Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Failure physics.
Rozprawy doktorskie na temat „Failure physics”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Failure physics”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Kodger, Thomas Edward. "Mechanical Failure in Colloidal Gels". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226100.
Pełny tekst źródłaStreszczenie:
When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis.
Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form them.
2
Thaduri, Adithya. "Physics-of-failure based performance modeling of critical electronic components". Doctoral thesis, Luleå tekniska universitet, Drift, underhåll och akustik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16877.
Pełny tekst źródłaStreszczenie:
Reliability prediction of the electronic components used in industrial safety systems requires high accuracy and compatibility with the working environment. The traditional reliability prediction methods that draw on standard handbooks such as MIL-HDBK 217F, Telcordia, PRISM etc., are not appropriate to determine the reliability indices of these components. For one thing, technology is constantly advancing; for another, the empirical data do not always match the actual working environment.The newest reliability prediction methodology, the physics-of-failure (PoF), emphasizes the root cause of failure, failure analysis, and failure mechanisms based on the analysis of parameter characteristics. It involves a focused examination of failure point locations, considering the fabrication technology, process, materials and circuit layout obtained from the manufacturer. This methodology is capable of providing recommendations for the increased reliability of components using intuitive analysis.However, there is a limitation: it is sometimes difficult to obtain manufacturer’s details for failure analysis and quality information. Several statistical and probability modeling methods can be performed on the experimental data of these components to measure the time to failure. These experiments can be conducted using the accelerated-testing of dominant stress parameters such as Voltage, Current, Temperature, Radiation etc.In this thesis, the combination of qualitative data from PoF approach and quantitative data from the statistical analysis is used to create a modified physics-of-failure approach. This methodology overcomes the limitations of the standard PoF approach as it involves detailed analysis of stress factors, data modeling and prediction. A decision support system is created to select the best option from failure data models, failure mechanisms, failure criteria and other factors to ensure a growth in reliability.In this study, the critical electronic components used in certain safety systems from different technologies are chosen for reliability prediction: Optocoupler, Constant Fraction Discriminator, BJT Transistor, Voltage Comparator, Voltage Follower and Instrumentation amplifier. The study finds that the modified physics-of-failure methodology provides more accurate reliability indices than the traditional approaches using field data. Stress based degradation models are developed for each of the components. The modified PoF models developed using Response Surface Regression and Support Vector Machine (SVM) show better performance.Godkänd; 2013; 20130813 (aditha); Tillkännagivande disputation 2013-08-23 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Adithya Thaduri Ämne: Drift och underhållsteknik/Operation and Maintenance Avhandling: Physics-of-Failure Based Performance Modeling of Critical Electronic Components Opponent: Professor Hoang Pham, Dept of Industrial and Systems Engineering, Rutgers, The State University of New Jersey, USA Ordförande: Professor Uday Kumar, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Torsdag den 12 september 2013, kl 10.00 Plats: F1031, Luleå tekniska universitet
3
Smith, Christopher John. "Holistic physics-of-failure approach to wind turbine power converter reliability". Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12567/.
Pełny tekst źródłaStreszczenie:
As the cost of wind energy becomes of increasing importance to the global surge of clean and green energy sources, the reliability-critical power converter is a target for vast improvements in availability through dedicated research. To this end, this thesis concentrates on providing a new holistic approach to converter reliability research to facilitate reliability increasing, cost reducing innovations unique to the wind industry. This holistic approach combines both computational and physical experimentation to provide a test bench for detailed reliability analysis of the converter power modules under the unique operating conditions of the wind turbine. The computational models include a detailed permanent magnet synchronous generator wind turbine with a power loss and thermal model representing the machine side converter power module response to varying wind turbine conditions. The supporting experimental test rig consists of an inexpensive, precise and extremely fast temperature measurement approach using a PbSe photoconductive infra-red sensor unique in the wind turbine reliability literature. This is used to measure spot temperatures on a modified power module to determine the junction temperature swings experienced during current cycling. A number of key conclusions have been made from this holistic approach. -Physics-of-failure analysis (and indeed any wind turbine power converter based reliability analysis) requires realistic wind speed data as the temporal changes in wind speed have a significant impact on the thermal loading on the devices. -The use of drive train modelling showed that the current throughput of the power converter is decoupled from the incoming wind speed due to drive train dynamics and control. Therefore, the power converter loading cannot be directly derived from the wind speed input without this modelling. -The minimum wind speed data frequency required for sufficiently accurate temperature profiles was determined, and the use of SCADA data for physics-of failure reliability studies was subsequently shown to be entirely inadequate. -The experimental emulation of the power converter validated a number of the aspects of the simulation work including the increase in temperature with wind speed and the detectability of temperature variations due to the current's fundamental frequency. Most importantly, this holistic approach provides an ideal test bench for optimising power converter designs for wind turbine, or for other industries with stochastic loading, conditions whilst maintaining or exceeding present reliability levels to reduce wind turbine's cost of energy, and therefore, society.
4
Gu, Jie. "Prognostics of solder joint reliability under vibration loading using physics of failure approach". College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9266.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
5
Qin, Jin. "A new physics-of-failure based VLSI circuits reliability simulation and prediction methodology". College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7410.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Reliability Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
6
Xin, Xudong. "An analytical and numerical analysis of dynamic failure based on the multi-physics involved /". free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3025668.
Pełny tekst źródła
7
Siddique, Shahnewaz. "Failure mechanisms of complex systems". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51831.
Pełny tekst źródłaStreszczenie:
Understanding the behavior of complex, large-scale, interconnected systems in a rigorous and structured manner is one of the most pressing scientific and technological challenges of current times. These systems include, among many others, transportation and communications systems, smart grids and power grids, financial markets etc. Failures of these systems have potentially enormous social, environmental and financial costs. In this work, we investigate the failure mechanisms of load-sharing complex systems. The systems are composed of multiple nodes or components whose failures are determined based on the interaction of their respective strengths and loads (or capacity and demand respectively) as well as the ability of a component to share its load with its neighbors when needed. Each component possesses a specific strength (capacity) and can be in one of three states: failed, damaged or functioning normally. The states are determined based on the load (demand) on the component.
We focus on two distinct mechanisms to model the interaction between components strengths and loads. The first, a Loss of Strength (LOS) model and the second, a Customer Service (CS) model. We implement both models on lattice and scale-free graph network topologies. The failure mechanisms of these two models demonstrate temporal scaling phenomena, phase transitions and multiple distinct failure modes excited by extremal dynamics. We find that the resiliency of these models is sensitive to the underlying network topology. For critical ranges of parameters the models demonstrate power law and exponential failure patterns. We find that the failure mechanisms of these models have parallels to failure mechanisms of critical infrastructure systems such as congestion in transportation networks, cascading failure in electrical power grids, creep-rupture in composite structures, and draw-downs in financial markets. Based on the different variants of failure, strategies for mitigating and postponing failure in these critical infrastructure systems can be formulated.
8
Hulman, Andrea. "Breaking Glass: Exploring the Relationship Between Kinetic Energy and Radial Fracturing in Plate Glass". Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/scripps_theses/95.
Pełny tekst źródłaStreszczenie:
When glass breaks from the impact of an object, it exhibits a distinctive shattering pattern comprised of two different regions. This pattern was investigated using experimental impacts and predicted using Young’s Modulus. Results were not as expected, and it is likely that there exists error in some measurements. Further investigation of this topic is recommended.
9
Starkey, Carl Alan. "Analysis of the Failure Modes of Twisted Fiber Structures". Marietta College Honors Theses / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=marhonors1210352501.
Pełny tekst źródła
10
Petel, Oren E. "A study of the failure mechanism of detonations in homogeneous and heterogeneous explosives /". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99530.
Pełny tekst źródłaStreszczenie:
The present study measured the critical diameter and critical thickness of a variety of explosives. The explosives tested included two "unstable" homogeneous explosives (nitromethane and a nitromethane/nitroethane blend); a model heterogeneous explosive consisting of a packed bed of glass beads (Φ ~ 80 μm) saturated with the homogeneous nitromethane/nitroethane blend; and a commercial heterogeneous explosive, Apex Elite(TM). The comparison of the critical diameter and thickness of an explosive is used to identify the dominant propagation and failure mechanisms of the various explosives. The ratio of critical diameter to critical thickness for nitromethane, the nitromethane/nitroethane blend, the beaded heterogeneous explosive, and Apex Elite(TM) were found to be 3.2 +/- 0.6, 3.6 +/- 0.4, 2.3 +/- 0.1, and 3.5 +/- 1.2 respectively. According to accepted detonation failure theories, the energy losses associated with detonation front curvature are responsible for detonation failure. The curvature model, which is elaborated upon in the present work, leads to a predicted critical diameter to critical thickness ratio of exactly 2. The present study has shown that the only explosive which follows the behaviour predicted by curvature failure models is the beaded heterogeneous explosive, which exhibits fine scale heterogeneities. This seems to indicate that unstable liquid explosives and heterogeneous explosives with large scale heterogeneities do not fail simply due to the wave front curvature, but rather by a local mechanism of failure and reinitiation which dominates the detonation propagation.
11
DeLone, Scott F. McDonald Scott P. "The role of teacher guidance and failure during inquiry based labs in the physics classroom". [University Park, Pa.] : Pennsylvania State University, 2009. http://honors.libraries.psu.edu/theses/approved/WorldWideIndex/EHT-18/index.html.
Pełny tekst źródła
12
Oh, Yoonchan. "Multi-physics investigation on the failure mechanism and short-time scale wave motion in flip-chip configuration". Texas A&M University, 2004. http://hdl.handle.net/1969.1/2719.
Pełny tekst źródłaStreszczenie:
The demands for higher clock speeds and larger current magnitude in high-performance flip-chip electronic packaging configurations of small footprint have inevitably raised the concern over rapid thermal transients and large thermal spatial gradients that could severely compromise package performance. Coupled electrical-thermal-mechanical multi-physics were explored to evaluate the concern and to establish the knowledge base necessary for improving flip-chip reliability. It was found that within the first few hundred nanoseconds upon power-on, there were fast attenuating, dispersive shock waves of extremely high frequency propagating in the package. The notions of high cycle fatigue, power density and joint time-frequency analysis were employed to characterize the waves and the various failure modes associated with the moving of these short-lived dynamical disturbances in bulk materials and along interfaces. A qualitative measure for failure was also developed which enables the extent of damages inflicted by short-time wave propagation to be calculated in the probability sense. Failure modes identified in this study are all in agreement with what have been observed in industry. This suggests that micron cracks or interfacial flaws initiated at the short-time scale would be further propagated by the CTE-induced thermal stresses at the long-time scale and result in eventual electrical disruptions.
Although epoxy-based underfills with fillers were shown to be effective in alleviating thermal stresses and improving solder joint fatigue performance in thermal cycling tests of long-time scale, underfill material viscoelasticity was found to be insignificant in attenuating short-time scale wave propagation. On the other hand, the inclusion of Cu interconnecting layers in flip-chips was shown to perform significantly better than Al layers in suppressing short-time scale effects. These results imply that, if improved flip-chip reliability is to be achieved, all packaging constituent materials need to be formulated to have well-defined short-time scale and long-time scale properties. In addition, the results also suggest that the composition and layout of all packaging components be optimized to achieve discouraging or suppressing short-time scale dynamic effects. In summary, results reported herein and numerical procedures developed for the research would not just render higher packaging manufacturing yield, but also bring out significant impact on packaging development, packaging material formulation and micro-circuit layout design.
13
Markgren, Jakob. "CFD Modelling of Pressure-control Devices in Substations". Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96455.
Pełny tekst źródła
14
Chamberlain, Samuel Seamore. "Development of a physics of failure model and quantitative assessment of the fire fatality risk of compressed natural gas bus cylinders". College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1711.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Reliability Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
15
Arwidson, Jonas. "Thermal Fatigue Life Prediction of Solder Joints in Avionics by Surrogate Modeling : A Contribution to Physics of Failure in Reliability Prediction". Doctoral thesis, Linköpings universitet, Fysik och elektroteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91903.
Pełny tekst źródłaStreszczenie:
Manufacturers of aerospace, defense, and high performance (ADHP) equipment are currently facing multiple challenges related to the reliability of electronic systems. The continuing reduction in size of electronic components combined with increasing clock frequencies and greater functionality, results in increased power density. As an effect, controlling the temperature of electronic components is central in electronic product development in order to maintain and potentially improve the reliability of the equipment. Simultaneously, the transition to lead-free electronic equipment will most probably propagate also to the ADHP industry. Compared to well-proven tin-lead solder, the knowledge about field operation reliability of lead-free solders is still limited, as well as the availability of damage evaluation models validated for field temperature conditions. Hence, the need to fill in several knowledge gaps related to reliability and reliability prediction of lead-free solder alloys is emphasized. Having perceived increasing problems experienced in the reliability of fielded equipment, the ADHP industry has suggested inclusion of physics-of-failure (PoF) in reliability prediction of electronics as one potential measure to improve the reliability of the electronic systems. This thesis aims to contribute to the development of reliable ADHP systems, with the main focus on electronic equipment for the aerospace industry. In order to accomplish this, the thesis provides design guidelines for power distribution on a double-sided printed circuit board assembly (PBA) as a measure to improve the thermal performance without increasing the weight of the system, and a novel, computationally efficient method for PoF-based evaluation of damage accumulation in solder joints in harsh, non-cyclic field operation temperature environments. Thermal fatigue failure mechanisms and state‑of‑the‑art thermal design and design tools are presented, with focus on the requirements that may arise from avionic use, such as low weight, high reliability, and ability to sustain functional during high vibration levels and high g-forces. Paper I, II, and III describes an in-depth investigation that has been performed utilizing advanced thermal modeling of power distribution on a double-sided PBA as a measure to improve the thermal performance of electronic modules. Paper IV contributes to increasing the accuracy of thermal fatigue life prediction in solder joints, by employing existing analytical models for predicting thermal fatigue life, but enhancing the prediction result by incorporating advanced thermal analysis in the procedure. Papers V and VI suggest and elaborate on a computational method that utilizes surrogate stress and strain modeling of a solder joint, to quickly evaluate the damage accumulated in a critical solder joint from non-cyclic, non-simplified field operation temperature profiles, with accuracy comparable to finite element modeling. The method has been tested on a ball grid array package with SnAgCu solder joints. This package is included in an extensive set of accelerated tests that helps to qualify certain packages and solder alloys for avionic use. The tests include -20°C to +80°C and -55°C to +125°C thermal cycling of a statistically sound population of a number of selected packages, assembled with SnAgCu, Sn100C, and SnPbAg solder alloys. Statistical analysis of the results confirms that the SnAgCu-alloy may outperform SnPbAg solder at moderate thermal loads on the solder joints. In Papers VII and VIII, the timeframe is extended to a future, in which validated life prediction models will be available, and the suggested method is expected to increase the accuracy of embedded prognostics of remaining useful thermal fatigue life of a critical solder joint. The key contribution of the thesis is the added value of the proposed computational method utilized in the design phase for electronic equipment. Due to its ability for time-efficient operation on uncompressed temperature data, the method gives contribution to the accuracy, and thereby also to the credibility, of reliability prediction of electronic packages in the design phase. This especially relates to applications where thermal fatigue is a dominant contributor to the damage of solder joints.
16
Kitto, Kirsty, i Kirsty Kitto@flinders edu au. "Modelling and Generating Complex Emergent Behaviour". Flinders University. School of Chemistry, Physics and Earth Sciences, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20060626.132947.
Pełny tekst źródłaStreszczenie:
Despite a general recognition of the importance of complex systems, there is a dearth of general models capable of describing their dynamics. This is attributed to a complexity scale; the models are attempting to describe systems at different parts of the scale and are hence not compatible. We require new models capable of describing complex behaviour at different points of the complexity scale. This work identifies, and proceeds to examine systems at the high end of the complexity scale, those which have not to date been well understood by our current modelling
methodology. It is shown that many such models exhibit what might be termed contextual dependency, and that it is precisely this feature which is not well understood by our current modelling methodology. A particular problem is
discussed; our apparent inability to generate systems which display high end complexity, exhibited by for example
the general failure of strong ALife. A new model, Process Physics, that has been developed at Flinders University is discussed, and arguments are presented that it exhibits high end complexity. The features of this model that
lead to its displaying such behaviour are discussed, and the generalisation of this model to a broader range of complex systems is attempted.
17
Rukavina, Ivan. "Cyber-physics intrinsic modelling for smart systems". Thesis, Compiègne, 2021. http://bibliotheque.utc.fr/EXPLOITATION/doc/IFD/2021COMP2581.
Pełny tekst źródłaStreszczenie:
Dans le cadre de cette thèse, une approche de calcul de couplage multi-échelle et multi-physique en 2D et en 3D est présentée. La modélisation multi-échelle d’une structure consiste de l’échelle macro qui représente la réponse homogénéisée de la structure entière, tandis que l’échelle micro peut capturer les détails du comportement à la petite échelle du matériau, où des mécanismes inélastiques, tels que la plasticité ou l’endommagement, peuvent être pris en compte. L’intérieur de chaque macro-élément est rempli par le maillage à l’échelle micro qui s’y adapte entièrement. Les deux échelles sont couplées à travers le champ de déplacements imposé à l’interface. Le calcul par éléments finis est effectué, en utilisant une procédure de solution operator-split sur les deux échelles. En 2D, une discontinuité dans le champ de déplacements est introduite à l’échelle macro dans un élément fini Q4, pour pouvoir capturer l’adoucissement comportement d’un matériau piézoélectrique. Un degré de liberté supplémentaire qui représente le voltage est ajouté aux noeuds des macro-éléments de tétraèdre et d’hexaèdre en 3D. La poutre de Timoshenko comportant un modèle de commutation de polarisation est utilisée à l’échelle micro. Également, une formulation multi-échelle de Hellinger-Reissner a été développée et implémentée pour un simple patch test en électrostatique. La procédure proposée est mise en œuvre dans le logiciel de calcul par éléments finis FEAP - Finite Element Analysis Program. Pour simuler le comportement aux deux échelles, FEAP est modifié, et deux versions différentes du code sont obtenues - macroFEAP et microFEAP. Le couplage de ces codes est réalisé avec Component Template Library - CTL qui rend possible l’échange d’informations entre les deux échelles. Les capacités de cette approche multi-échelle en 2D et en 3D sont démontrées dans un environnement purement mécanique, mais aussi multi-physique. La formulation théorique et l’application algorithmique sont présentées, et les avantages de la méthode multi-échelle pour la modélisation des matériaux hétérogènes sont illustrés avec plusieurs exemples numériquesIn this thesis, a multi-scale and multi-physics coupling computation procedure for a 2D and 3D setting is presented. When modeling the behavior of a structure by a multi-scale method, the macro-scale is used to describe the homogenized response of the structure, and the micro-scale to describe the details of the behavior on the smaller scale of the material where some inelastic mechanisms, like damage or plasticity, can be taken into account. The micro-scale mesh is defined for each macro-scale element in a way to fit entirely inside it. The two scales are coupled by imposing a constraint on the displacement field over their interface. The computation is performed using the operator split solution procedure on both scales, using the standard finite element method. In a 2D setting, an embedded discontinuity is implemented in the Q4 macroscale element to capture the softening behavior happening on the micro-scale. For the micro-scale element, a constant strain triangle (CST) is used. In a 3D setting, a macro-scale tetrahedral and hexahedral elements are developed, while on the micro-scale Timoshenko beam finite elements are used. This multi-scale methodology is extended with a multi-physics functionality, to simulate the behavior of a piezoelectric material. An additional degree of freedom (voltage) is added on the nodes of the 3D macro-scale tetrahedral and hexahedral elements. For the micro-scale element, a Timoshenko beam element with added polarization switching model is used. Also, a multi-scale Hellinger- Reissner formulation for electrostatics has been developed and implemented for a simple electrostatic patch test. For implementing the proposed procedure, Finite Element Analysis Program (FEAP) is used. To simulate the behavior on both macro and micro-scale, FEAP is modified and two different version of FEAP code are implemented – macroFEAP and microFEAP. For coupling, the two codes are exchanging information between them, and Component Template Library (CTL) is used. The capabilities of the proposed multi-scale approach in a 2D and 3D pure mechanics settings, but also multi-physics environment have been shown. The theoretical formulation and algorithmic implementation are described, and the advantages of the multi-scale approach for modeling heterogeneous materials are shown on several numerical examples
18
Matsson, Ingvar. "Studies of Nuclear Fuel Performance Using On-site Gamma-ray Spectroscopy and In-pile Measurements". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6912.
Pełny tekst źródła
19
CASTANHEIRA, MYRTHES. "Analise dos mecanismos de degradacao de varetas combustiveis falhadas em reatores PWR". reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11141.
Pełny tekst źródłaStreszczenie:
Made available in DSpace on 2014-10-09T12:48:49Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:01:00Z (GMT). No. of bitstreams: 1 09634.pdf: 20502766 bytes, checksum: d7ca137617708ba2e112264b734dcd6e (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
20
Procopio, Marcos Vinicios Rabelo. "FRACASSO UNIVERSITÁRIO: UM ESTUDO SOBRE A PERMANÊNCIA DOS ACADÊMICOS DO CURSO DE FÍSICA". Pontifícia Universidade Católica de Goiás, 2014. http://localhost:8080/tede/handle/tede/711.
Pełny tekst źródłaStreszczenie:
Made available in DSpace on 2016-07-27T13:44:53Z (GMT). No. of bitstreams: 1
MARCOS VINICIOS RABELO PROCOPIO.pdf: 2565052 bytes, checksum: 28d41a89feb201236a4777de11b6efde (MD5)
Previous issue date: 2014-08-28The university failure has become a problem of world order, especially in courses such as Physics. Facing this reality, after an exhaustive search in databases of theses and dissertations and journals of the past two decades, we find a paucity of studies that seek to understand more fully the factors that can influence the performance of this academic. In this context, this research aimed to clarify the relationship between the prevailing social, cultural and academic conditions between the reprobate and academic failure in the higher physics courses at universities in Brazil and Portugal. To this end, we seek as a research field two public universities located in the central region of two Portuguese-speaking countries with nearby cultures: Brazil and Portugal. The research methodology consisted of two studies, the first was called primary that led to the creation of a data collection instrument, called QACSCA (Questionnaire Assessment of social, cultural and academic conditions) and the second titled principal that has a sample of 118 students of physics at the Federal University of Goiás and 97 at the University of Aveiro. The method used for data analysis triangulation was sequenced, and the preliminary study conducted a qualitative analysis and quantitative main study and still looked like Bourdieu, Charlot Vygotsky and theoretical support for discussion of results. So that the discussion of the collected data was performed with the support of four categories of analysis "Subject", "Subject and Society", "Relationship to know" and "Zone proximal student" which emerged from the discussions related to the conduct subject in interaction with certain groups, the tensions and conflicts in the field where cultural capital is distributed, desire and knowledge in order to enrich the human heritage and mediation between capital that the student has to enter the university and the he can acquire during their university studies. The data showed that 78.6% of the sample are students who have had 2-7 failures during the course, which leads them to extrapolate up to two years the period of four years of training. It was evident that the disciplines of Mathematics & Physics, together confirmed its high failure rate reaching 53.3% of the total sample, 31.6% and 23.7% identified as grounds of abandonment, rejection or locking disciplines, respectively, learning difficulties, transportation, relationships and the negative performance in different subjects, little time for studies and prior to his entry into the physics course unsatisfactory training. Discussions explained the complexity of the problem linked to the theoretical support failure used in order to raise the habitus, the field and the area of academic development that presents during his journey in physics courses.
O fracasso universitário se tornou um problema de ordem mundial, sobretudo em cursos como o de Física. Frente a esta realidade, após uma exaustiva pesquisa nos bancos de teses e dissertações e nos periódicos das duas últimas décadas, verificamos uma escassez de estudos que buscam compreender mais a fundo os fatores que podem influenciar no desempenho desse acadêmico. Neste contexto, objetivamos nesta investigação explicitar as relações existentes entre as condições sociais, culturais e acadêmicas preponderantes entre os acadêmicos reprovados e o fracasso nos cursos superiores de Física das universidades do Brasil e de Portugal. Para tal, buscamos como campo de pesquisa duas universidades públicas localizadas na região central de dois países de língua portuguesa com culturas próximas: Brasil e Portugal. A metodologia da investigação foi composta por dois estudos, o primeiro foi chamado de preliminar que propiciou a criação de um instrumento de coleta de dados, denominado de QACSCA (Questionário de Avaliação das condições sociais, culturais e acadêmicas) e o segundo intitulado de principal que conta com uma amostra de 118 acadêmicos do curso de Física da Universidade Federal de Goiás e 97 da Universidade de Aveiro. O método utilizado para a análise dos dados foi a triangulação sequenciada, sendo que no estudo preliminar realizou-se a análise qualitativa e no estudo principal a quantitativa e ainda buscou-se como suporte teórico Bourdieu, Charlot e Vygotsky para discussão dos resultados. De forma que a discussão sobre os dados coletados foi realizada com o apoio de quatro categorias de análise Sujeito , Sujeito e Sociedade , Relação com o saber e Zona proximal do aluno das quais surgiram discussões relacionadas às condutas do sujeito em interação com determinados grupos, as tensões e os conflitos existentes no campo onde o capital cultural é distribuído, o desejo e o saber de forma a enriquecer o patrimônio humano e a mediação entre o capital que o aluno apresenta ao entrar na universidade e o que ele pode adquirir durante o seu percurso universitário. Os dados demonstraram que 78,6% da amostra são de alunos que tiveram de 2 a 7 reprovações no decorrer do curso, o que os leva a extrapolar em até dois anos o período de 4 anos de formação. Evidenciou-se que as disciplinas de Cálculo e Física, juntas confirmaram seu alto índice de reprovação chegando a 53,3% do total da amostra, 31,6% e 23,7% apontaram como motivo de abandono, reprovação ou trancamento das disciplinas, respectivamente, as dificuldades de aprendizagem, de transporte, de relacionamento e o desempenho negativo nas disciplinas, pouco tempo para estudos e uma formação insatisfatória anterior à sua entrada no curso de Física. As discussões explicitaram a complexidade do problema do fracasso atrelada ao suporte teórico utilizado de forma a levantar o habitus, o campo e a zona de desenvolvimento que o acadêmico apresenta durante seu percurso nos cursos de Física.
21
Kiilavuori, Kai. "Physical training in chronic heart failure". Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/kiilavuori/.
Pełny tekst źródła
22
Dwyer, Todd Douglas. "Development of a physical slope failure model /". free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421132.
Pełny tekst źródła
23
Souguir, Sabri. "Simulation numérique de l'initiation de la rupture à l'échelle atomique". Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1082/document.
Pełny tekst źródłaStreszczenie:
En ingénierie mécanique, la rupture des matériaux est un risque qu'il convient d'anticiper et qui reste aujourd'hui une menace pour les structures. La rupture des systèmes pré-fissurés a lieu quand l'énergie libérée par la propagation de la fissure préexistante excède un seuil critique (taux de restitution d'énergie) qui représente une propriété du matériau. Au contraire, la rupture de systèmes sans défauts préexistants survient lorsque la contrainte appliquée atteint la résistance, également propriété du matériau. L'existence de deux critères pour la rupture semble indiquer des mécanismes d'amorçage différents, ce qui soulève la question des cas réels intermédiaires qui présentent des concentrations de contrainte modérées. Différentes approches existantes sont cohérentes avec les deux situations limites mais il n'y a pas de consensus clair dans la communauté scientifique. Dans cette thèse, nous étudions les mécanismes de la rupture fragile à l'échelle atomique afin d'en comprendre l'origine physique pour différentes concentrations de contraintes. La rupture provient de la rupture des liaisons à l'échelle atomique. Nous utilisons donc des techniques de simulation moléculaire pour étudier la physique élémentaire de l'initiation de la rupture fragile. Dans ce but, on étudie deux types de structure atomique. Le premier est un matériau modèle à maille triangulaire, dont le potentiel permet d'interpréter analytiquement, et avec précision, les résultats des simulations moléculaires. L'étude est étendue à un système plus réel : le graphène. Ce matériau, qui présente une résistance élevée au regard de sa faible ténacité, a l'une des plus petites tailles de zone d'élaboration par rapport aux autres matériaux fragiles, ce qui permet d'appliquer numériquement les concepts de la rupture fragile jusqu'à l'échelle nanométrique de la simulation moléculaire. On s'intéresse dans un premier temps à la rupture des matériaux à 0K. À cette température, un système atomique est en équilibre statique. La rupture peut donc être traitée comme une instabilité. L'analyse du profil énergétique du système atomique fournit un moyen d'identifier les mécanismes de rupture. Nous montrons qu'on peut identifier la rupture en cherchant les valeurs propres nulles ou négative de la matrice hessienne. Les vecteurs propres correspondants indiquent les modes de rupture et montrent l'apparition de bandes de transition entre mouvements de groupes d'atomes pour des systèmes intacts, dont la largeur rappelle la longueur d'élaboration, généralement introduite dans des théories macroscopiques d'initiation de la rupture. On étudie aussi l'effet de la présence de défauts sur les modes d'instabilité et leur dégénérescence. Cette étude fournit une technique générale pour identifier les mécanismes d'initiation de rupture quelle que soit la concentration de contrainte dans la structure. On s'intéresse ensuite aux températures non nulles. On étudie les effets combinés de la température, de la taille du système et du taux de chargement. En partant de la théorie cinétique, nous montrons qu'il existe des lois d'échelle générales fournissant une équivalence taille-vitesse de chargement-température et permettant de relier résistance et ténacité à la limite à 0K. La différence entre la loi d'échelle en résistance et celle en ténacité réside dans le fait que la rupture ne soit pas sensible à la taille du système pré-fissuré mais au nombre de pointes de fissure. Cela indique une différence statistique essentielle entre la rupture en résistance et la fracture ce qui permet de mieux comprendre la transition de l'une à l'autre. Dans l'esprit de mieux comprendre la transition entre les deux types de rupture, on traite le cas de trous elliptiques à différents rapports d'aspects et on analyse en même temps l'effet de cette transition sur les modes d'instabilité. On étudie en dernière partie, l'effet des surfaces libres et les différents paramètres caractérisant cette situationIn mechanical engineering, failure is a risk that must be anticipated and is still a threat for structures. The failure of pre-cracked systems occurs when the energy released by the propagation of the pre-existing crack exceeds a critical threshold (Griffith's energy release rate) which represents a property of the material. On the contrary, the failure of systems without pre-existing defects occurs when the applied stress reaches the strength, also property of the material. The existence of two criteria for failure suggests different driving mechanisms, which raises the question of intermediate cases with moderate stress concentrations. Different existing approaches are consistent with the two limit cases but there is no clear consensus in the scientific community.In this work, we study the mechanisms of brittle failure on the atomic scale in order to understand the underlying physical mechanisms. Macroscopic failure comes from the breaking of bonds at the atomic scale. We therefore use molecular simulation techniques to study the elementary physics of brittle failure initiation. Two types of atomic structure are studied. The first one is a triangular lattice toy model whose simplicity allows precise analytical interpretation of the molecular simulation results. The study is extended to a more realistic system: graphene. This material, which has a high strength and a rather low toughness in comparison, has one of the smallest process zones compared to other brittle materials, which makes it possible to apply the concepts of brittle failure up to the nanometric scale of molecular simulation. We first investigate the failure of materials at 0K. At this temperature, an atomic system is in static equilibrium. The breaking of bonds can be treated as instability. The analysis of the energy profile of the atomic system provides a means of identifying the mechanisms of failure. We show that we can identify failure initiation by looking for negative or zero eigenvalues of the Hessian matrix. The corresponding eigenvectors indicate the modes of failure and show the appearance of transition bands between motions of groups of atoms for intact systems, whose width recalls the size of the process zone, generally introduced in macroscopic theories of failure initiation. We also study the effect of defects on the instability modes and their degeneracy. This study provides a general technique to capture fracture initiation mechanisms irrespective of the stress concentration in the structure. We focus afterwards on finite temperatures. We study the combined effects of temperature, system size and loading rate. Starting from the kinetic theory, we identify general scaling laws providing a size-loading rate-temperature equivalence and relating the strength and toughness to the limit at 0K. The difference between the scaling law of strength and that of toughness lies in the fact that failure is not sensitive to the size of the pre-cracked system but to the number of crack tips. This indicates an essential statistical difference between strength and fracture failures which makes it possible to better understand the transition from one to the other.In order to better understand the transition between the two types of failure, we treat the case of elliptic holes with different aspect ratios and we focus at the same time on the effect of this transition on instability modes. We study in the last part the case of non-periodic structures with free surfaces. We determine the various parameters characterizing this situation and the effect of the presence of surface phenomena on instability modes
24
Rimmer, R. A. "High power microwave window failures". Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233566.
Pełny tekst źródła
25
Haedtke, Christine Ann. "Pain and physical activity in older depressed heart failure patients". Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/5943.
Pełny tekst źródłaStreszczenie:
Background/Significance: Heart failure patients have high mortality, co-morbidity, hospitalization rates, costs and numerous recommendations to follow. Non-cardiac pain is common and an additional compounding problem as it decreases heart failure (HF) patients’ ability to follow recommendations, decreases quality of life and increases the likelihood of being hospitalized. When depression is combined with HF and pain, patients are even less able to follow recommendations, treatment plans, and self-care behaviors.
Exercise is an important, low-cost intervention for pain that has considerably fewer adverse effects/interactions than pharmacologic therapies. Given the low rates of participation in exercise and the many barriers that discourage exercise participation, an essential first step is to establish current physical activity levels and how pain may further influence potential engagement in exercise programs.
Objectives: To characterize and describe: the experience of pain, pain management, the self-reported physical activity level including relationships between pain intensity, pain interference, total activity time, sitting time, perceptions of exercise, and depression, in older depressed HF participants.
Methods: This prospective cross-sectional study analyzed data from 62 participants with depression and Class II-IV HF. Data from the Brief Pain Inventory, Rand 36, International Physical Activity Questionnaire, Beck Depression Inventory II, and Exercise and Pain Management Questionnaire were used in the analysis.
Results: The majority of depressed HF patients had moderate to severe pain intensity and interference and no differences were found in demographics between those who had pain and those who didn’t. Depression level did not have an additional impact on pain intensity or pain interference. Non-pharmacological treatments were severely underutilized. The majority of participants think exercise will be helpful to treat their pain. The most common barriers to exercise for depressed HF patients include: shortness of breath 72%, having no one to exercise with 59%, fatigue 56%, other health conditions 56%, and the weather is too hot or too cold 55%. Those who had higher pain intensity, pain interference, or depression scores were not more likely to say exercise would be unhelpful than those with lower scores. Lastly, the majority would like to be more physically active.
Conclusion: The prevalence of pain reported by this sample, combined with the diverse pain locations, reliance on medications that are well-known for having untoward side-effects in this population, and generally poor treatment responses reported, make it clear that thorough pain assessment and additional pain treatment strategies are needed to decrease the impact of pain on this population. Findings suggest that depressed patients with HF believe exercise would be helpful to treat their pain and would also like to be more active. Decreasing sitting time and increasing light activity levels hold promise to improve pain and depression symptoms. Interventions to increase physical activity levels that are acceptable to depressed HF patients need to be identified and offered as treatment options, including referral to cardiac rehab as an important starting point for individualized support and education that may increase long-term adherence.
26
Raischel, Frank. "Fibre models for shear failure and plasticity". [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29619.
Pełny tekst źródła
27
Huang, Zhen. "Interdependent Cyber Physical Systems: Robustness and Cascading Failures". Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31517.
Pełny tekst źródłaStreszczenie:
The cyber-physical systems (CPS), such as smart grid and intelligent transportation system, permeate into our modern societies recently. The infrastructures in such systems are closely interconnected and related, e.g., the intelligent transportation system is based on the reliable communication system, which requires the stable electricity provided by power grid for the proper function. We call such mutually related systems interdependent networks.
This thesis addresses the cascading failure issue in interdependent cyber physical system. We consider CPS as a system that consists of physical-resource and computational-resource networks. The failure in physical-resource network might cause the failures in computational-resource network, and vice versa. This failure may recursively occur and cause a sequence of failures in both networks.
In this thesis, we propose two novel interdependence models that better capture the interdependent networks. Then, we study the effect of cascading failures using percolation theory and present the detailed mathematical analysis on failure propagation in the system. By calculating the size of functioning parts in both networks, we analyze the robustness of our models against the random attacks and failures.
The cascading failures in smart grid is also investigated, where two types of cascading failures are mixed. We estimate how the node tolerance parameter T (ratio of capacity to initial workload) affect the system performance. This thesis also explores the small clusters. We give insightful views on small cluster in interdependent networks, under different interdependence models and network topologies.
28
Echeverri, Duarte Andres. "Etude de la Fiabilité des Transistors HEMTs AIGaN/GaN de puissance en condition opérationnelle". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR014.
Pełny tekst źródłaStreszczenie:
Cette thèse porte sur l’étude des transistors de puissance à haute mobilité électronique en Nitrure de Gallium à enrichissement récemment apparus sur le marché. Ces travaux se focalisent sur l’analyse physique de la défaillance lors du vieillissement de ces composants sous des profils de mission réels de commutation. Un banc de stress a été conçu et construit, permettant d’imposer des conditions de fonctionnement réel sur le transistor sans utiliser des charges et donc en minimisant la consommation d’énergie. Une autre originalité de ce banc est qu’il contient des transistors témoin qui subissent une partie du stress imposé au transistor sous test, aidant ainsi à la compréhension des dégradations. Les composants vieillis sont caractérisés électriquement pour établir les modes de défaillance. Des méthodes de décapsulation de composants et de préparation d’échantillons mulit-échelle (mm au nm) ont été également développées afin d’accéder à la zone active des transistors. Par l’analyse de la microstructure des dispositifs, avec des techniques de photoémission spectrale, microscopie électronique à balayage et en transmission, les mécanismes de défaillance sont déterminés et la corrélation avec les modes dedéfaillance correspondants est réaliséeThis PhD Thesis is about the reliability of enhancement Gallium Nitride high electron mobility power transistors, recently on the market. This work is focused on physics of failure analysis on aged devices under real mission switching profiles. A novel stress bench able of stablish real operating conditions on a transistor without using a load, so minimizing energy consumption. Also, the circuit has two additional devices that undergo separate current and voltage stresses and are used for better understanding of degradations on main device under test. Electric characterization of aged devices allows determination of failure modes. Decapsulation and sample preparation procedures at different scales were developed to access the active zone of the devices and perform micro-structural analyses by the means of spectral photoemission, scanning and transmission electronic microscopies. Then, failure mechanisms are correlated with the corresponding modes
29
Meyur, Rounak. "Cascading Events in the Aftermath of a Targeted Physical Attack on the Power Grid". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/88795.
Pełny tekst źródłaStreszczenie:
This work studies the consequences of a human-initiated targeted attack on the electric power
system by simulating the detonation of a bomb at one or more substations in and around
Washington DC. An AC power flow based transient analysis on a realistic power grid model
of Eastern Interconnection is considered to study the cascading events. A detailed model
of control and protection system in the power grid is considered to ensure the accurate
representation of cascading outages. Particularly, the problem of identifying a set of k
critical nodes, whose failure/attack leads to the maximum adverse impact on the power
system has been analyzed in detail. It is observed that a greedy approach yields node sets
with higher criticality than a degree-based approach, which has been suggested in many
prior works. Furthermore, it is seen that the impact of a targeted attack exhibits a nonmonotonic
behavior as a function of the target set size k. The consideration of hidden failures
in the protective relays has revealed that the outage of certain lines/buses in the course of
cascading events can save the power grid from a system collapse. Finally, a comparison with
the DC steady state analysis of cascading events shows that a transient stability assessment
is necessary to obtain the complete picture of cascading events in the aftermath of a targeted
attack on the power grid.M.S.
The modern day power system has been identified as a critical infrastructure providing crucial support to the economy of a country. Prior experience has shown that a small failure of a component in the power grid can lead to widespread cascading events and eventually result in a blackout. Such failures can be triggered by devastating damage due to a natural calamity or because of a targeted adversarial attack on certain points in the power system. Given limited budget to avoid widespread cascading failures in the network, an important problem would be to identify critical components in the power system. In this research an attempt has been made to replicate the actual power system conditions as accurately as possible to study the impact of a targeted adversarial attack on different points in the network. Three heuristics have been proposed to identify critical nodes in the network and their performance has been discussed. The case studies of cascading events have been performed on a synthetic power system network of Washington DC to achieve the actual system conditions of an operating power grid.
30
Sunny, Danish Ali [Verfasser], i Guido [Akademischer Betreuer] Schneider. "Failure of amplitude equations / Danish Ali Sunny ; Betreuer: Guido Schneider". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1124465987/34.
Pełny tekst źródła
31
Da, Re Gregory 1970. "Physical mechanisms controlling the pre-failure stress-strain behavior of frozen sand". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/31088.
Pełny tekst źródłaStreszczenie:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references.
The physical mechanisms controlling the pre-failure stress-strain behavior of frozen sands are investigated in triaxial compression. The pre-failure, or small strain behavior (Ea
Ph.D.
32
Tailony, Rauf. "Internal Combustion Engine Cold Test Driveline Modeling, Analysis and Development". University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1564765172535669.
Pełny tekst źródła
33
Nichols, Melanie. "Self-Efficacy, Outcome Expectancy, and Fear of Failure as Predictors of Physical Activity". OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/638.
Pełny tekst źródłaStreszczenie:
Though the benefits of physical activity are well-studied and accepted, researchers have struggled to identify models of health behavior that accurately predict exercise. This dissertation utilized two components of Bandura's Social-Cognitive Model (self-efficacy and outcome expectancies) and added the construct of fear of failure in order to evaluate what factors influence an individual's decision to exercise or avoid physical activity. Self-report data assessing fear or failure, self-efficacy, outcome expectancies, and physical activity were collected from 248 university students and were analyzed using structural equation modeling techniques in order to evaluate the proposed structural model, which hypothesized that fear of failure would negatively relate to the two Social-Cognitive variables, which were expected to positively predict physical activity engagement. Results revealed that although fear of failure did not add significantly to the Social-Cognitive model, a large portion of the variance in physical activity (i.e., 49%) could be accounted for by the model. Additionally, results indicated that outcome expectancies were a much stronger predictor of physical activity than self-efficacy beliefs. This finding is discussed in relation to how individual differences and genetics may influence how rewarding or aversive individuals find exercising. Implications for intervention and directions for future study, including alternate ways of adding affect to the model are discussed.
34
Barlow, Jacob Aaron. "Heart Failure Readmission and the Physical Activity Vital Sign (PAVS): Is There a Relationship?" BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/9064.
Pełny tekst źródłaStreszczenie:
Background - Heart failure costs Americans billions of dollars a year and takes a toll on the patients afflicted by the disease. Recent changes in how healthcare systems and providers are reimbursed have motivated them to find new ways to prevent heart failure readmission. There is no cure for heart failure so healthcare providers try to help patients manage their symptoms. Physical activity is one of the interventions healthcare providers recommend for their patients in the management of heart failure. The Physical Activity Vital Sign is a tool that can be quickly administer and has significant validity. Objective - The purpose of our research is to determine if physical activity, as measured by the Physical Activity Vital Sign, influences 30-day heart failure readmissions. Methods - A retrospective chart review was used to evaluate patients' charts that had a heart failure admission between January 1, 2016 and August 31, 2018. We used multiple regression to analyze how the Physical Activity Vital Sign predicts 30-day heart failure readmission rates, while controlling for age, sex, race, ejection fraction, body mass index, length of hospital stay, brain natriuretic peptide, and compliance with the heart failure core measures. Results - Data was analyzed from 270 heart failure admissions in the study period. The average duration of moderate intensity PA was 20.9 minutes per week; just less than three minutes per day on average. A Pearson Correlation matrix illustrated significant relationships between some of the independent variables. Multiple linear regression demonstrated p=0.376, which was statistically insignificant. Conclusions - The study did not find a significant relationship between physical activity, as measured by the Physical Activity Vital Sign, and heart failure readmissions but physical activity remains important in managing heart failure.
35
Adsett, Julie. "Exercise rehabilitation for people with stable heart failure". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/384942.
Pełny tekst źródłaStreszczenie:
Heart failure (HF) is a condition associated with high levels of morbidity and mortality.
For people with this condition, exercise training is recommended as part of standard
management as it improves exercise capacity, symptoms and quality of life and has been
shown to reduce hospital readmissions. Guidelines recommend that all people with stable
HF undertake 150 minutes of moderate intensity activity per week. For many years,
centre-based exercise programmes, such as cardiac rehabilitation or HF rehabilitation,
have been the traditional approach to assist individuals to meet these guidelines, however,
uptake at these programmes is poor and recent studies suggest that fewer than 40% of
people with HF meet recommended physical activity targets. This has led clinicians to
deviate from the traditional “one size fits all” exercise model in search of strategies which
assist individuals to attend these programmes, and to explore alternative exercise
opportunities to increase exercise adherence at scale. This thesis aims to examine
exercise participation in people recently hospitalised with HF and to explore aquatic
exercise training as a potential exercise option for this population.
The thesis was developed in two parts. Section one (Studies 1 and 2) aimed to describe
and identify variables associated with exercise participation and exercise capacity
measured by six minute walk distance (6MWD). Study 1 was a sub-study of the
EJECTION-HF trial, a multicentre randomised controlled trial which investigated the
impact of supervised exercise training in addition to a disease management programme,
in people recently hospitalised with HF. Primary outcomes of this trial were death or
readmission at 12 months. The objectives of Study 1 were to describe exercise
participation in this clinical HF population and to identify variables related to exercise
participation which are associated with improvements in 6MWD. Data were available
from 140 participants for exercise programme attendance variables and 117 participants
for self-reported physical activity undertaken outside of the health facility. Results
confirm that exercise participation is poor in this cohort and also identify that frequent
exercise programme attendance (at least weekly) and being physically active (meeting
exercise guidelines), are independently and strongly associated with improvements in
functional exercise capacity. Following on from these findings, Study 2 sought to identify predictors of these important
variables (frequent programme attendance and meeting exercise guidelines). This study
was also a sub-study of the EJECTION-HF trial. Variables entered into logistic regression
models included common participant and clinical characteristics such as age, gender, HF
aetiology, disease severity, new versus decompensated HF, presence of comorbidities and
baseline physical activity. Findings indicated that a new diagnosis of HF was strongly
associated with exercise participation, including both frequent programme attendance as
well as meeting exercise guidelines. Baseline physical activity was also associated with
being physically active at 12 weeks. Results from Studies 1 and 2 provide new insight
into the exercise behaviour of people recently hospitalised with HF and identify
opportunities for clinicians to target exercise services more specifically for greatest effect.
Section two of this thesis (Studies 3, 4 and 5) aimed to explore the safety, efficacy and
acceptability of aquatic exercise training, thus determining if this mode of exercise is a
suitable option for people with HF seeking alternative exercise opportunities. Study 3
produced a systematic review and meta-analysis of existing literature with particular
focus on the impact of aquatic exercise training interventions on exercise capacity, muscle
strength, quality of life, haemodynamics and B-type natriuretic peptide. Compared to no
exercise controls, aquatic exercise training was associated with significant improvements
in exercise capacity, muscle strength and quality of life. Based upon the absence of
serious adverse events in any of the small studies included in this review, aquatic exercise
training was deemed to be safe for people with stable HF.
Study 4 expanded on these findings by examining the feasibility and efficacy of aquatic
exercise training, compared to a land-based exercise programme in a clinical
environment. This randomised 2x2 crossover design trial enrolled people with HF who
were in an exercise training maintenance phase at two metropolitan hospitals and
compared six weeks of aquatic and land-based exercise training with respect to 6MWD,
grip strength and measures of balance. Data from 51 participants with stable HF
confirmed that aquatic exercise training is safe and feasible in a clinical environment and
is equally effective as land-based exercise training for maintaining each of the outcome
measures listed above. This study also identified biventricular HF as a potential contraindication
for this type of exercise training. Study 5 aimed to explore individuals’ experiences with aquatic and land-based exercise
training using a mixed methods approach to determine acceptability of aquatic exercise
training in a clinical HF population. A purpose designed questionnaire gathered
information about experiences and preferences and was provided to participants at the
completion of Study 4. Semi-structured interviews further explored perceptions,
experiences, motivators and barriers to exercise participation in 14 participants, seven of
whom had chosen not to participate in the aquatic programme. Results confirmed that
people with HF perceive aquatic exercise training to be a safe, acceptable and enjoyable
mode of exercise, similar to land-based exercise training. Latent fatigue was identified as
a common symptom of the aquatic programme, however was not associated with the landbased
programme. Important motivators for exercise participation were identified and
included a skilled and compassionate workforce, sense of safety, perceived benefit,
programme tailored to the individual and sense of inclusiveness and enjoyment. These
themes were common to both exercise interventions.
This thesis, in two sections, examines concepts relating to exercise adherence in a clinical
HF population. Section one describes exercise behaviour in people recently hospitalised
with HF and explores variables associated with both exercise participation and outcomes.
These studies identified potentially vulnerable groups who are less likely to meet
recommended exercise guidelines, thus presenting opportunity to tailor services for best
effect. Section two presents a comprehensive report of aquatic exercise training in people
with HF. Based upon these results, this mode of exercise is safe, effective and acceptable
for people with stable HF and thus provides an additional and viable option for these
individuals to be physically active.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School Allied Health Sciences
Griffith Health
Full Text
36
Іванович, Рудик Юрій, Victor Kuts, Andrii Gavryliuk, Roman Naumchuk i Rudyk Yuriy. "Required safety component of automotive cyber - physical systems". Thesis, IEEЕ, 2020. http://hdl.handle.net/123456789/7112.
Pełny tekst źródłaStreszczenie:
This identification of possible hazardous events
is a task for the risk assessment procedure. Current practices
for risk characterization is based on known threats, their
consequences and damage expectance.
Modern technologies, such as electric, electronic, cyber-
physical systems etc. have proven the existence of many
challenges related to their practice and there is potential for
improvements in how the hazard characterization can be
conducted.
Our purpose is to present practical methods that should
be applied for hazardous events’ evaluation. Features of
electric vehicles fire safety studies are highlighted. These
approaches include furthering studies regarding rankings of
risk factors and assumptions supporting the analysis.
Focusing on events not included in existing studies. A simple
example is used to illustrate how efficiency is reduced, due to
a lack of a proper risk assessment perception from a safety
standpoint. For the wires with polyvinylchloride insulating
material with a most widespread cross-sectional areas the
temperature and the time of the reaches the point of self-
ignition was established.
37
Sridharan, Sivakumar. "Energy expenditure in kidney failure : implications for management". Thesis, University of Hertfordshire, 2014. http://hdl.handle.net/2299/14932.
Pełny tekst źródłaStreszczenie:
Renal replacement therapy, in the form of dialysis or transplantation, is the cornerstone of management for end-stage renal disease. UK renal registry shows nearly half of those needing renal replacement therapy are treated by dialysis – predominantly by haemodialysis. Patients on renal replacement therapy have increased mortality risk compared to age matched general population. Moreover, some specific subgroups of patients on haemodialysis have increased risk of mortality than expected. The survival benefit seen in women in the general population is attenuated resulting in similar survival for men and women on haemodialysis therapy. In addition, obese individuals and those of non-Caucasian origin have better survival outcome. Though the underlying reason for these findings is not clear and is likely to be multi-factorial, it has been hypothesised that this paradox could be due to the current practice of normalising dialysis dose to total body water. A number of metabolic factors – body surface area, resting energy expenditure and total energy expenditure – have been proposed as alternative to total body water for scaling dialysis dose. There were two overarching aims of this work – one was to study the effect of declining renal function on resting and total energy expenditure and to study the influence of various energy expenditure measures on uraemic toxin generation. The second was to study the impact on survival outcome of using these alternate parameters for normalising dialysis dose and to derive dialysis dose adjustments based on these metabolic parameters. In order to study these aims, studies were designed to explore different aspects of energy expenditure measures along with a longitudinal study to examine the impact of these parameters on survival outcome. The relationship between energy metabolism, body composition and uraemic toxin generation was studied with a retrospective analysis of 166 haemodialysis patients in whom urea generation rate was used as surrogate marker of uraemic toxin generation. It was found that total energy expenditure and fat-free mass predicted uraemic toxin generation after adjustment for other relevant variables. This study provided the preliminary data which was useful in designing further studies for this work. The effect of renal function on resting and total energy expenditure was studied in 80 patients with varying stages of chronic kidney disease who were not on renal replacement therapy. Resting and total energy expenditures were measured directly using gold-standard methods. It was found that declining renal function did not have a significant influence on either of these measures. This supports the hypothesis that metabolic rate is the driving force for glomerular filtration rate and not vice-versa. The directly measured energy expenditure measures were also found to have a moderately strong relationship with urea generation rate in these patients not on renal replacement therapy. The impact of physical activity on uraemic toxin generation, and thereby dialysis requirement, was studied in a prospective cross-sectional study of 120 haemodialysis patients in whom the physical activity was measured by an accelerometer device. Results from the study showed physical activity level to be a significant predictor of uraemic toxin generation after adjustment for gender and body size differences. This study results stressed the importance of adjusting dialysis dose based on individual’s physical activity level. To study the impact of using metabolic factors as normalising parameter for scaling dialysis dose on survival outcome, a large-scale longitudinal study was conducted with 1500 maintenance haemodialysis patients recruited for the study. Dialysis dose-related parameters and survival outcomes were collected at baseline and at various time points during the follow-up period of 18 months. Study results were analysed in two parts - the theoretical basis for using these metabolic factors as scaling parameters was explored which showed that current minimum target dialysis dose risks under-dialysis in certain subgroups of patients and using these alternative parameters may provide a more equivalent dialysis dose across individuals of different body sizes and gender. With these results arguing for potential use of the alternative parameters, the impact on survival of using them were examined. It was found that all three parameters performed better than the current parameter (total body water) with regards to predicting mortality. Total energy expenditure was found to be the best parameter with the lowest hazard ratio for risk of death. The study data was also analysed to derive an algorithm for adjustment of minimum target dialysis dose based on body size and physical activity level. This newly derived minimum dose target was also shown to impact on survival with those underdialysed based on this criteria having poorer survival outcomes. To understand the impact of whole body protein turnover on resting energy expenditure and uraemic toxin generation, a cross-sectional study was conducted on 12 patients with advanced CKD – 6 each in pre-dialysis CKD and haemodialysis group. It was found that haemodialysis patients had higher rate of protein turnover compared to pre-dialysis patients. Whole body protein turnover was found to contribute significantly to resting energy expenditure and had a moderately strong relationship with urea generation rate. In the course of these studies, two questionnaire tools have been validated for use for clinical and research purposes – one is a self-report comorbidity questionnaire and the other, the Recent Physical Activity Questionnaire. The comorbidity questionnaire was developed as part of this work and was validated against Charlson Comorbidity Index. The Recent Physical Activity Questionnaire was validated for physical activity data collection and energy expenditure calculation against the gold-standard doubly labelled water method. In conclusion, it has been demonstrated that metabolic factors such as body surface area, resting energy expenditure and total energy expenditure are more closely related to uraemic toxin generation compared to total body water. It has also been demonstrated that physical activity contributes to metabolic waste production and may necessitate changes in dialysis requirement. It has been shown that these metabolic factors, when used as scaling parameter for dialysis dosing, may predict survival better than the current parameter in use. The algorithm for dialysis dose adjustment and the questionnaires validated in this work have provided novel tools for further research studies and clinical practice. The central hypothesis of this work is that some metabolic factors may be better markers of uraemic toxin generation compared to total body water. It is hypothesised that modifications in dialysis practice based on these factors may improve the quality of haemodialysis and favourably impact on survival outcome for patients with end-stage renal disease. The work presented here largely supports this hypothesis.
38
Andersen, Kasper. "Physical Activity and Cardiovascular Disease". Doctoral thesis, Uppsala universitet, Institutionen för medicinska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-217309.
Pełny tekst źródłaStreszczenie:
The aim was to investigate associations of fitness and types and levels of physical activity with subsequent risk of cardiovascular disease. Four large-scale longitudinal cohort studies were used. The exposures were different measures related to physical activity and the outcomes were obtained through linkage to the Swedish In-Patient Register. In a cohort of 466 elderly men without pre-existing cardiovascular disease, we found that skeletal muscle morphology was associated with risk of cardiovascular events. A high amount of type I (slow-twitch, oxidative) skeletal muscle fibres was associated with lower risk of cardiovascular events and high amount of type IIx was associated with higher risk of cardiovascular events. This association was only seen among physically active men. Among 39,805 participants in a fundraising event, higher levels of both total and leisure time physical activity were associated with lower risk of heart failure. The associations were strongest for leisure time physical activity. In a cohort of 53,755 participants in the 90 km skiing event Vasaloppet, a higher number of completed races was associated with higher risk of atrial fibrillation and a higher risk of bradyarrhythmias. Further, better relative performance was associated with a higher risk of bradyarrhythmias. Among 1,26 million Swedish 18-year-old men, exercise capacity and muscle strength were independently associated with lower risk of vascular disease. The associations were seen across a range of major vascular disease events (ischemic heart disease, heart failure, stroke and cardiovascular death). Further, high exercise capacity was associated with higher risk of atrial fibrillation and a U-shaped association with bradyarrhythmias was found. Higher muscle strength was associated with lower risk of bradyarrhythmias and lower risk of ventricular arrhythmias. These findings suggest a higher rate of atrial fibrillation with higher levels of physical activity. The higher risk of atrial fibrillation does not appear to lead to a higher risk of stroke. In contrast, we found a strong inverse association of higher exercise capacity and muscle strength with vascular disease. Further, high exercise capacity and muscle strength are related to lower risk of cardiovascular death, including arrhythmia deaths. From a population perspective, the total impact of physical activity on cardiovascular disease is positive.
39
Hardy, Nicholas Richard. "The physical modelling of two phase releases following the sudden failure of pressurised vessels". Thesis, London South Bank University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291746.
Pełny tekst źródła
40
Garcia, Sarah L. "THE CONTRIBUTION OF PHYSICAL ACTIVITY TO NEUROIMAGING INDICES AND COGNITIVE FUNCTION IN HEART FAILURE". Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1366114402.
Pełny tekst źródła
41
Heiwe, Susanne. "Experienced physical functioning and effects of resistance training in patients with chronic kidney disease /". Stockholm, 2004. http://diss.kib.ki.se/2004/91-7349-865-3/.
Pełny tekst źródła
42
Song, Mingxia. "Propagation des plasmons de surface dans des nanofils métalliques". Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00842236.
Pełny tekst źródłaStreszczenie:
Plasmonic circuitry is considered as a promising solution-effectivetechnology for miniaturizing and integrating the next generation ofoptical nano-devices. The realization of a practical plasmonic circuitry strongly depends on the complete understanding of the propagation properties of two key elements: surface plasmons and electrons. The critical part constituting the plasmonic circuitry is a waveguide which can sustain the two information-carriers simultaneously. Therefore, we present in this thesis the investigations on the propagation of surface plasmons and the co-propagation of surface plasmons and electrons in single crystalline metal nanowires. This thesis is therefore divided into two parts. In the first part, we investigate surface plasmons propagating in individual thick penta-twinned crystalline silver nanowires using dual-plane leakage radiation microscopy. The effective index and the losses of the mode are determined by measuring the wave vector content of the light emitted in the substrate. Surface plasmon mode is determined by numerical simulations and an analogy is drawn with molecular orbitals compound with similar symmetry. Leaky and bound modes selected by polarization inhomogeneity are demonstrated. We further investigate the effect of wire geometry (length, diameter) on the effective index and propagation losses. On the basis of the results obtained during the first part, we further investigate the effect of an electron flow on surface plasmon properties. We investigate to what extend surface plasmons and current-carrying electrons interfere in such a shared circuitry. By synchronously recording surface plasmons and electrical output characteristics of single crystalline silver and gold nanowires, we determine the limiting factors hindering the co-propagation of electrical current and surface plasmons in these nanoscale circuits. Analysis of wave vector distributions in Fourier images indicates that the effect of current flow on surface plasmons propagation is reflected by the morphological change during the electromigration process. We further investigate the possible crosstalk between co-propagating electrons and surface plasmons by applying alternating current bias
43
Du, HuiYun. "Home-Heart-Walk : evaluation of an intervention to promote and monitor physical activity". Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1961.
Pełny tekst źródłaStreszczenie:
Chronic heart failure is a complex and multifaceted clinical syndrome and impacts adversely on health related quality of life and also increases the risk of hospitalisation and major acute coronary events. Self-care in chronic heart failure requires lifestyle changes, such as dietary modifications, fluid restriction, medication adherence and increasing physical activity. Enhancing self-care has been shown to result in better health outcomes and improved quality of life. Promoting better self-care is an important and effective strategy in chronic heart failure management. Exercise and physical activity are part of best practice recommendation. Despite compelling evidence to support the benefits of physical activity in improving functional capacity and quality of life, physical activity adherence remains low. Many people find following physical activity recommendations more difficult than following their medication regime, fluid restriction and diet. To date, the majority of interventions have focused on improving physical functioning of people living with CHF involving supervised, clinic based exercise programs although the benefits for home based programs is evident. Nevertheless, the impressive gains people have achieved through physical activity programs are often lost as many fail to maintain a physically active lifestyle after they complete the program.Based upon a comprehensive literature review and theoretical framework, the Home-Heart-Walk has been developed. The Home-Heart-Walk is a novel theoretically informed self-monitoring intervention, sought to promote physical functioning in people living with chronic heart failure. This model is a self-administered intervention adapted from the standard six minute walk test. It comprised six months of weekly Home-Heart-Walk and monthly telephone follow-up. This doctoral project evaluated the effect of the Home-Heart-Walk in promoting physical functioning in a group people with chronic heart failure.Based upon a comprehensive literature review and theoretical framework, the Home-Heart-Walk has been developed. The Home-Heart-Walk is a novel theoretically informed self-monitoring intervention, sought to promote physical functioning in people living with chronic heart failure. This model is a self-administered intervention adapted from the standard six minute walk test. It comprised six months of weekly Home-Heart-Walk and monthly telephone follow-up. This doctoral project evaluated the effect of the Home-Heart-Walk in promoting physical functioning in a group people with chronic heart failure.Participants were followed up at three months and six months. The primary outcome was the physical function domain of the Medical Outcome Study Short Form-36. Secondary outcomes included the Six Minute Walk Test (6MWT) distance, European Heart Failure Self-care Behaviour Scale, Bandura’s exercise self-efficacy, generic health related quality of life (Medical Outcome Study Short Form-36) and disease specific (Minnesota Living with Heart Failure Questionnaire) as well as Physical Activity Scale.This thesis presents the conceptual underpinnings of a theoretically derived intervention, clinical trial methodology and the interim analysis of the first 67 participants who have completed the six-month study. All participants’ data were analysed on the basis of the intention to treat principle. Despite there were no statistical or clinical significant difference observed between the intervention and the control group at six-month follow-up, there was a significant increase in the 6MWT distance over the six-month study period, in the intervention group (p=0.05). A trend of improved self-reported health related quality of life was also observed in the intervention group, with a slight decreased Minnesota Living with Heart Failure Questionnaire score (baseline: 45.4 [95% CI: 37.0-53.9]; three-month: 41.7 [95% CI: 32.6-50.9]) compared to the clinically meaningful deterioration (increased score) in the control group (baseline: 36.3 [95% CI: 27.8-44.7]; three-month: 43.9 [95% CI: 35.3-52.6]). The deterioration observed in control group was sustained at six-month follow-up. Similarly, score in self-care behaviour was also slightly decreased (improvement) (26.2 [95% CI: 23.4-29.0] to 24.0 [95% CI: 21.6-26.3]) compared to a slight increase (deterioration) in the control group (25.6 [95% CI: 22.9-28.5] to 26.5 [95% CI: 23.4-29.6]), over the study period.While results from this interim analysis will not allow conclusion to be made on the effectiveness of the Home-Heart-Walk, they have provided preliminary data and insights into the challenge of promoting physical functioning in people living with chronic heart failure. This study highlights the challenges of achieving long-term physical activity adherence for people living with CHF. This has been demonstrated in recruitment challenges, and the refractory dimension of increasing physical activity.
44
Pap, Ilona. "Productivity enhancement in optical semiconductor manufacturing: Early warning of failures in BHet laser fabrication". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26736.
Pełny tekst źródłaStreszczenie:
There are unique challenges in the fabrication and testing of optical semiconductor devices because, unlike typical silicon semiconductor devices, which can be tested cost-effectively on the wafer, many optical devices can only be 'fully' tested once the individual die is bonded to a heat sink. As a result, both the manufacturing process and test strategy need to be capable of predicting yields and product quality attributes based on limited sampling from a batch of the product. The large number of product quality and process variables that are measured for each device when it is manufactured makes it almost impractical to manually analyze them for valuable decision-making information. There is a need for understanding the complex, interactive effects of process variables on the product quality variables as well as automated analysis and discovery tools for extracting useful knowledge from the raw data. Such knowledge could have a significant impact on productivity and quality improvement. The objective of the present study is to identify useful correlations amongst the numerous process variables and to develop simple empirical models to predict important process quality indicators.
Quality is assessed using statistical data analysis, focusing on the primary functions of major failures. Validation of the data set also demonstrated that linear models were accurate in predicting new data points for some of the output variables, whereas the variation of some output variables could not be explained using the available industrial data bank. Some models were powerful in making predictions and to provide a clearer insight in determining the key factors in manufacturing of BHet. BHet is a directly modulated laser operating at 2.5 Gb/s and reaches up to 360 km. Application of this research for failure prediction at an early stage of the manufacturing line could result in a dramatic reduction in the number of defective wafers that are completely processed and thereby lowering the overall manufacturing cost.
45
Klompstra, Leonie. "Physical activity in patients with heart failure : motivations, self-efficacy and the potential of exergaming". Doctoral thesis, Linköpings universitet, Avdelningen för omvårdnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-130933.
Pełny tekst źródłaStreszczenie:
Background: Adherence to recommendations for physical activity is low in patients with heart failure (HF). It is essential to explore to what extent and why patients with HF are physically active. Self-efficacy and motivation for physical activity are important in becoming more physically active, but the role of self-efficacy in the relationship between motivation and physical activity in patients with HF is unknown. Alternative approaches to motivate and increase self-efficacy to exercise are needed. One of these alternatives might be using exergames (games to improve physical exercise). Therefore, it is important to obtain more knowledge on the potential of exergaming to increase physical activity. The overall aim was to describe the physical activity in patients with HF, with special focus on motivations and self-efficacy in physical activity, and to describe the potential of exergaming to improve exercise capacity. Methods: Study I (n = 154) and II (n = 101) in this thesis had a cross-sectional survey design. Study III (n = 32) was a 12-week pilot intervention study, including an exergame platform at home, with a pretest-posttest design. Study IV (n = 14) described the experiences of exergaming in patients who participated in the intervention group of a randomized controlled study in which they had access to an exergame platform at home. Results: In total, 34% of the patients with HF had a low level of physical activity, 46% had a moderate level, 23% reported a high level. Higher education, higher selfefficacy, and higher motivation were significantly associated with a higher amount of physical activity. Barriers to exercise were reported to be difficult to overcome and psychological motivations were the most important motivations to be physically active. Women had significantly higher total motivation to be physically active. Self-efficacy mediated the relationship between exercise motivation and physical activity; motivation leads to a higher self-efficacy towards physical activity. More than half of the patients significantly increased their exercise capacity after 12 weeks of using an exergame platform at home. Lower NYHA-class and shorter time since diagnosis were factors significantly related to the increase in exercise capacity. The mean time spent exergaming was 28 minutes per day. Having grandchildren and being male were related to more time spent exergaming. The analysis of the qualitative data resulted in three categories describing patients’ experience of exergaming: (i) making exergaming work, (ii) added value of exergaming, (iii) no appeal of exergaming. Conclusion: One-third of the patients with HF had a low level of physical activity in their daily life. Level of education, exercise self-efficacy, and motivation were important factors to take into account when advising patients with HF about physical activity. In addition to a high level of motivation to be physically active, it is important that patients with HF have a high degree of exercise self-efficacy. Exergaming has the potential to increase exercise capacity in patients with HF. The results also showed that this technology might be suitable for some patients while others may prefer other kinds of physical activity.Achtergrond: Het aantal patiënten met hartfalen (HF) dat zich kan houden aan de aanbevolen lichamelijke activiteit is over het algemeen klein. Het is essentieel om te onderzoeken in hoeverre en waarom patiënten met HF lichamelijk actief zijn. Het hebben van self-efficacy (een persoonlijke overtuiging dat hij/zij capabel is om te doen wat nodig is om een taak te volbrengen op een bepaald kwaliteitsniveau) en motivatie voor lichamelijke activiteit is belangrijk om meer lichamelijk actief te worden. Het is echter niet duidelijk wat de rol van self-efficacy is in relatie tot motivatie en lichamelijke activiteit bij patiënten met HF. Alternatieve benaderingen zijn nodig om patiënten te motiveren lichamelijk actiever te zijn en de self-efficacy te verhogen. Een van de mogelijke alternatieven om patiënten met HF te helpen lichamelijk actiever te zijn is de inzet van exergames: computerspellen om fysieke activiteit te bevorderen. Er is tot nu toe geen onderzoek is gedaan naar de inzet van exergaming bij patiënten met hartfalen en de mogelijkheden van exergaming om patiënten te stimuleren tot meer lichamelijke activiteit. Het doel van dit proefschrift is het beschrijven van de lichamelijke activiteit van patiënten met HF met extra aandacht voor de motivatie en self-efficacy ten opzichte van lichamelijke activiteit. Een tweede doel is om inzicht te krijgen in de mogelijkheid om exergaming te gebruiken om de lichamelijke activiteit van patiënten met HF te verhogen. Methode: In dit proefschrift worden gegevens van 4 studies beschreven (studie I-IV). Studie I (n = 154) en II (n = 101) hebben een crosssectioneel survey design. Studie III (n = 32) is een 12 weken durende pilot-interventie studie met een pretest-posttest design waarbij patiënten 12 weken lang een exergame platform thuis konden gebruiken. Studie IV (n = 14) beschrijft de ervaringen van patiënten die deelnamen aan de interventiegroep van een gerandomiseerde studie waarin zij een exergame platform thuis kregen. Resultaten: In totaal hebben 34% van alle patiënten met hartfalen een laag niveau van lichamelijke activiteit, 46% had een matig niveau, en 23% een hoog niveau. Een hoger opleidingsniveau, self-efficacy en motivatie significant werd geassocieerd met een hogere hoeveelheid lichamelijke activiteit. Het bleek dat barrières voor fysieke activiteit moeilijk te overbruggen waren. Met betrekking tot motivatie, bleek dat psychologische motivatie de belangrijkste drijfveer was om fysiek actief te zijn. Verder bleek dat vrouwen een significant hogere motivatie voor fysieke activiteit hebben dan mannen. Een ander belangrijk resultaat was dat self-efficacy de relatie tussen motivatie en lichamelijke activiteit beïnvloedt; motivatie leidt tot een hogere self-efficacy wat leidt tot hogere fysieke activiteit. Met betrekking tot de resultaten van exergaming bleek dat de inspanningscapaciteit van meer dan de helft van de patiënten aanzienlijk was toegenomen na 12 weken gebruik gemaakt te hebben van een exergame platform thuis. Patiënten met een lager NYHA-klasse en een kortere tijd na de diagnose verhogen significant meer hun inspanningscapaciteit. Ook bleek dat het hebben van een partner en kleinkinderen gerelateerd is aan meer tijd besteden aan exergaming. De analyse van de ervaringen van patiënten in de kwalitatieve studie resulteerde in drie categorieën: (i) zorgen dat exergaming werkt, (ii) toegevoegde waarde van exergaming, (iii) geen aantrekking tot exergaming. Conclusie: Een derde van de patiënten met HF heeft een laag niveau van lichamelijke activiteit in hun dagelijks leven. Opleidingsniveau, self-efficacy en motivatie zijn belangrijke factoren om rekening mee te houden bij het geven van advies aan patiënten met HF betreffende fysieke activiteit. Naast een hoge motivatie tot bewegen is het belangrijk dat patiënten met HF een hoog niveau van self-efficacy hebben om fysiek actief te zijn. Exergaming heeft potentie om inspanningscapaciteit bij patiënten met HF te verhogen. Uit de resultaten blijkt ook dat deze techniek geschikt is voor een deel van de patiënten, terwijl een deel van de patiënten wellicht liever andere vormen van lichamelijke activiteit beoefenen.
46
Ingemarsson, Philip. "The daily movement pattern and physical activity in a Swedish cohort of heart failure patients". Thesis, Örebro universitet, Institutionen för medicinska vetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-82520.
Pełny tekst źródła
47
Nordmann, Joachim [Verfasser], Holm [Gutachter] Altenbach i Manja [Gutachter] Krüger. "Failure analysis of coatings under thermo-mechanical loading / Joachim Nordmann ; Gutachter: Holm Altenbach, Manja Krüger". Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/122003519X/34.
Pełny tekst źródła
48
Eastwood, Bryan J. "A fundamental study of the electrochemical failure mechanisms of a novel impressed current cathodic protection system". Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363874.
Pełny tekst źródła
49
Suna, Jessica Mary. "The effect of exercise training on sleep quality in heart failure". Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/61340/1/Jessica_Suna_Thesis.pdf.
Pełny tekst źródłaStreszczenie:
Background: Heart failure is a serious condition estimated to affect 1.5-2.0% of the Australian population with a point prevalence of approximately 1% in people aged 50-59 years, 10% in people aged 65 years or more and over 50% in people aged 85 years or over (National Heart Foundation of Australian and the Cardiac Society of Australia and New Zealand, 2006). Sleep disturbances are a common complaint of persons with heart failure. Disturbances of sleep can worsen heart failure symptoms, impair independence, reduce quality of life and lead to increased health care utilisation in patients with heart failure. Previous studies have identified exercise as a possible treatment for poor sleep in patients without cardiac disease however there is limited evidence of the effect of this form of treatment in heart failure.
Aim: The primary objective of this study was to examine the effect of a supervised, hospital-based exercise training programme on subjective sleep quality in heart failure patients. Secondary objectives were to examine the association between changes in sleep quality and changes in depression, exercise performance and body mass index.
Methods: The sample for the study was recruited from metropolitan and regional heart failure services across Brisbane, Queensland. Patients with a recent heart failure related hospital admission who met study inclusion criteria were recruited. Participants were screened by specialist heart failure exercise staff at each site to ensure exercise safety prior to study enrolment. Demographic data, medical history, medications, Pittsburgh Sleep Quality Index score, Geriatric Depression Score, exercise performance (six minute walk test), weight and height were collected at Baseline. Pittsburgh Sleep Quality Index score, Geriatric Depression Score, exercise performance and weight were repeated at 3 months.
One hundred and six patients admitted to hospital with heart failure were randomly allocated to a 3-month disease-based management programme of education and self-management support including standard exercise advice (Control) or to the same disease management programme as the Control group with the addition of a tailored physical activity program (Intervention). The intervention consisted of 1 hour of aerobic and resistance exercise twice a week. Programs were designed and supervised by an exercise specialist. The main outcome measure was achievement of a clinically significant change (.3 points) in global Pittsburgh Sleep Quality score.
Results: Intervention group participants reported significantly greater clinical improvement in global sleep quality than Control (p=0.016). These patients also exhibited significant improvements in component sleep disturbance (p=0.004), component sleep quality (p=0.015) and global sleep quality (p=0.032) after 3 months of supervised exercise intervention. Improvements in sleep quality correlated with improvements in depression (p<0.001) and six minute walk distance (p=0.04). When study results were examined categorically, with subjects classified as either "poor" or "good" sleepers, subjects in the Control group were significantly more likely to report "poor" sleep at 3 months (p=0.039) while Intervention participants were likely to report "good" sleep at this time (p=0.08).
Conclusion: Three months of supervised, hospital based, aerobic and resistance exercise training improved subjective sleep quality in patients with heart failure. This is the first randomised controlled trial to examine the role of aerobic and resistance exercise training in the improvement of sleep quality for patients with this disease.
While this study establishes exercise as a therapy for poor sleep quality, further research is needed to investigate the effect of exercise training on objective parameters of sleep in this population.
50
Anagnostakis, Ioannis. "Experimental investigations of physical factors which influence runoff and failure behavior of aircraft de-icing fluids". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/49934.
Pełny tekst źródła