To see the other types of publications on this topic, follow the link: Deterioration.
Dissertations / Theses on the topic 'Deterioration'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Deterioration.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hine, Brooke A. "Growth and Deterioration." VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/929.
Full textAbstract:
I use porcelain clay because it allows me to focus on the subtle color shifts between white, beige, and gray. The forms I make in clay are associated with tangled roots, naked tree branches, hollow logs, and bones. I reveal this with a dense mass of curvilinear hollow forms that stack into a rhythmic linkage. They twist and turn, relying on gravity to dictate their structure within the installation. The ends of some are closed while others remain open to expose their interior. The tearing and perforations on the surface of each piece are employed to emphasize deterioration. In opposition to the tearing and perforations, I also add concave lines to the surface creating a flowing moving force. The surface is both visually active and smooth, allowing the eye to roam and focus on specific areas. I'm also working with the accumulation of pieces to communicate growth. The individual pieces rest on one another, growing into an interlocking structure. The pedestal is a formal presentation that is specific to the space. For this installation, I wanted to make the work monumental by elevating an accumulation of pieces. When walking around the artwork, there's an opening in the platform for one person to walk in and be surrounded by the two sides of the piece. The work is above eye level and surrounds the viewer at both sides. I want people to view the mass from the outside, but to also have an experience from the inside.
2
Yu, Ji. "Railway trackbed deterioration." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37918/.
Full textAbstract:
In this thesis, the main objective is to identify the resilient deformation behaviour of rail trackbed especially in ballast and calculate the stress distribution. A purpose-designed three dimensional Finite Element railway trackbed model is presented in which linear elastic behaviour is assumed in all parts of the model. The study has also evaluated the effects of different variables including moving load magnitude, loading speed and stiffness of materials on stress conditions and deflections based. A comprehensive literature review on a wide background of railway trackbed has been carried out. Railway ballast specifications, deformation mechanisms, resilient and permanent deformation behaviour of granular material, introduction of fouling material and its influence on ballast behaviour are explained to provide the basis for trackbed analysis. Results show that a higher vertical displacement underneath the sleeper may occur when the loading speed is higher than 120km/h. Also, higher speed and Young’s modulus of ballast can result in higher damaging stresses. A stiffer subgrade can result in less rotation of sleeper. A significant effect of subgrade stiffness on stress paths and rotation of sleeper can only be found when Young’s modulus of subgrade is in a low level. Stiffer rail pad can lead ballast element get cracked more easily. Softer pad results in less damaging stresses. In addition, there is no obvious change of either the stress ratio or sleeper rotation as stiffness of the ballast increased.
3
O'Donnell, Johanna. "Predicting heart failure deterioration." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:f7e51226-128b-44eb-8f6a-557f1d0c9a53.
Full textAbstract:
Chronic heart failure (HF) is a condition that affects more than 900,000 people in the UK. Mortality rates associated with the condition are high, with nearly 20% of patients dying within one year of diagnosis. Continuous monitoring and risk stratification can help identify patients at risk of deterioration and may consequently improve patients' likelihood of survival. Current repeated-measure risk stratification techniques for HF patients often rely on subjective perception of symptoms, such as breathlessness, and markers of fluid retention in the body (e.g. weight). Despite the common use of such markers, studies have shown that they offer limited effectiveness in predicting HF-related events. This thesis set out to identify and evaluate new markers for repeated-measure risk stratification of HF patients. It started with an exploration of traditional HF measurements, including weight, blood pressure, heart rate and symptom scores, and aimed to improve the performance of these measurements using a data-driven approach. A multi-variate model was developed from data acquired during a randomised controlled trial of remotely-monitored HF patients. The rare occurrence of HF-related adverse events during the trial required the developement of a careful methodology. This methodology helped identify the markers with most predictive ability, which achieved moderate performance at identifying patients at risk of HF-related adverse events, clearly outperforming commonly-used thresholds. Subsequently, this thesis explored the potential value of additional, accelerometer-derived physical activity (PA) and sleep markers. For this purpose, the ability of accelerometer-derived markers to differentiate between individuals with and without HF was evaluated. It was found that markers that summarise the frequency and duration of different PA intensities performed best at differentiating between the two groups and may therefore be most suitable for future use in repeated-measure applications. As part of the analysis of accelerometer-derived HF markers, a gap in the methodology of automated accelerometer processing was identified, namely the need for self-reported sleep-onset and wake-up information. As a result, Chapter 5 of this thesis describes the development and evaluation of a data-driven solution for this problem. In summary, this thesis explored both traditional and new, accelerometer-derived markers for the early detection of HF deterioration. It utilised sound methodology to overcome limitations faced by sparse and unbalanced datasets and filled a methodological gap in the processing of signals from wrist-worn accelerometers.
4
Kendall, Michaela. "Particulate pollution and stone deterioration." Thesis, Middlesex University, 1998. http://eprints.mdx.ac.uk/13410/.
Full textAbstract:
The soiling and damage of building surfaces may be enhanced by particulate air pollution, reducing the aesthetic value and lifetimes of historic buildings and monuments. This thesis focuses on the deposition of atmospheric particulate material to building surfaces and identifies potential sources of this material. It also identifies environmental factors influencing two deterioration effects: surface soiling and black crust growth. Two soiling models have been compared to assess their effectiveness in predicting the soiling rates of two materials - stone and wood - in five cities in Europe. An exponential decay model was found to describe the reduction of reflectance well at two of these sites, while a square root relationship is not as effective. Different measures of weekly particulate concentration were not statistically related to soiling rate, whereas S02, rainfall, and temperature were statistically related to reflectance loss over time. Wind speed and solar insolation were also indicated to influence soiling rates. Concentrations of total suspended particulate (TSP), particulate elemental carbon (PEC), total organic carbon (TOC) and thirty-nine particulate-associated hydrocarbons were measured in airborne particles at two sites in London, for one year. These hydrocarbons were also measured in black crusts from St Paul's Cathedral to relate atmospheric and deposited material, and to identify potential sources of the deposited particulate matter. Detailed scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis of black crust \ similarly indicated potential sources of these deposition layers. Analysis revealed the complex structure of these crusts, comprising gypsum "growth stems ", calcite and large numbers of particles mainly originating from oil combustion. Hydrocarbon analysis supported the fact that oil combustion - probably at Bank power station - was the dominant source of this deposited layer. Other particle morphologies were commonly found, such as those typical of coal combustion and diesel engine exhaust. Metals analyses also indicated other possible sources such as vehicles.
5
Zwebek, A. I. "Combined Cycle Performance Deterioration Analysis." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/10462.
Full textAbstract:
Combined
cycles are subject to degradations and hence performance deterioration.
According to the author's survey nothing was found in the open literature on this
subject. Therefore, it was anticipated that it would be of great achievement if a tool for
analysing and diagnosing the deterioration of combined cycle could be produced. So
this thesis
presents a procedure for combined cycle performance analysis and fault
diagnostic by way of simulation.
l order to
accomplish this task successfully it was necessary to developed two
pieces of software. These are STEAMOMATCH for steam cycle performance
deterioration
analysis, and GOTRESS for GPA of any system. STEAMOMATCH, which
is built on the basics of combined cycle thermodynamics, can simulate up to three levels
of
pressure with reheat. On the other hand GOTRESS uses a Gas Path Analysis
technique that enables the user the choice of conducting either linear or non-linear GPA
at the same time. I both cases single or multiple fault can be diagnosed. GOTRESS
was built in such a
way that it makes it a generalised code that can be used not only for
combined
cycle but to diagnose a wide range of power cycle plants.
The deterioration simulation results of the gas turbine power plant showed that the
isentropic efficiency deterioration of the turbine unit has the uppermost sever effect on
overall
gas turbine power output and thermal efficiency. This is also the case with
steam turbine
(bottoming) cycle power and Rankine efficiency. Also, the simulation
results obtained showed that the relationship between the gas turbine size and its
performance deterioration is almost constant, i.e. performance deterioration follows the
plant's size. Among the two major gas turbine parameters that affects the steam
bottoming cycle performance of a CCGT power plant, the gas turbine exhaust
temperature has a predominant effect on steam cycle efficiency over the exhaust mass
flow.' As a
general result, the obtained simulation results showed that the behaviour of
CCGT
power plant performance is more affected by gas turbine cycle conditions than
by steam turbine cycle conditions. The obtained results showed that GPA can be
successfully applied to either gas turbine cycle, steam turbine cycle, or the combination
of the two in a form of combined cycle. The GPA diagnostic results obtained showed
that it would be
possible to detect some faults that might occur within the gas turbine
that is a
part of a combined cycle power plant by monitoring the dependent parameters
of the steam turbine (bottoming) cycle such as live steam pressure and temperature and
steam turbine
power. In contrast, it would not been possible to detect the problems
(implanted faults) that might occur within the steam turbine by monitoring the
dependent parameters of the gas turbine unit.
6
Liu, Yawen. "Prediction of pavement surface deterioration." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/48275/.
Full textAbstract:
Prediction of pavement performance is important to pavement engineers. Pavement surface deterioration is a dynamic and complicated process. Moisture damage and fatigue are considered as two major causes of pavement deterioration. During a pavement’s service life, the presence of water can lead to loss of stiffness and strength of the asphalt pavement structure. Apart from that, the presence of water can accelerate the propagation and severity of already existing distress. High tensile strain at the bottom of an asphalt layer results fatigue cracking in a pavement. The goal of this research was to develop a series of computational models to predict pavement surface deterioration under the effects of moisture and traffic. The first task was to calculate the pavement surface water pressure under a moving tyre. The water is compressed underneath the tyres, generating a water pressure pulse. This pressure allows surface water to penetrate into the pavement structure. Then the asphalt pavement internal structure (voids distribution) was determined and the water pressure distribution inside the pavement structure was calculated for both fully saturated and partially saturated condition using the surface water pressure. The water pressure expands the voids inside the pavement. Consequently, stress and strain at the edge of the voids, due to frequent traffic passes can lead to failure of the pavement. A ravelling failure probability line was then predicted with the help of cavity expansion theory and asphalt crack propagation law. The case study for the performance of four different asphalt types (HRA, SMA, AC, DBM) using the failure probability calculation shows a good correspondence with their real performance which indicates that this process of predicting failure probability is generally acceptable.
7
Monavari, Benyamin. "SHM-based structural deterioration assessment." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132660/1/Benyamin%20Monavari%20Thesis.pdf.
Full textAbstract:
This research has successfully developed an effective methodology to detect and locate deterioration as well as estimate its severity in the presence of environmental and operational (E&O) variations and high level of measurement noise. It developed a novel data normalization procedure to diminish the E&O variations and high level of noise content; and developed thirteen time-series based deterioration indicators to detect deterioration. The proposed methods were verified utilising measured data from different numerically simulated case studies and laboratory tests, and their efficiency is demonstrated using data acquired from a real-world instrumented building.
8
Suntaranond, Suphap. "Processes influencing deterioration in stored seeds." Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phs958.pdf.
Full text
9
Fairbrass, Sheila Ann. "Surface deterioration of poly(vinyl chloride)." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322083.
Full text
10
Strong, Neil. "Fungal deterioration of sawn softwood lumber." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285528.
Full textAbstract:
The colonisation of freshly sawn Corsican pine lumber by sapstain and mould fungi was investigated at a sawmill in Hampshire, UK. Three repeat trials encompassing the different seasons of the year were carried out over two years. Results show that fungal colonisation of sawn lumber is dependent on the effect of time of year. Sawlogs were stored for different intervals up to 16 weeks before conversion to boards. Boards were then stored for up to 12 weeks after milling and sampled every 4 weeks to determine the effect of timber ageing on fungal colonisation up to 28 weeks after felling. The metabolic activity of wood cells over the period after felling of the original tree was also measured. It was evident that the defacement of boards reached maximum levels after 12 weeks exposure irrespective of seasonal influences. Initial levels of fungal growth on lumber were reduced if the boards were milled from logs stored for a period prior to conversion. Investigations into the metabolic activity of the wood cells revealed significant levels of respiration taking place up to 28 weeks after felling of the original tree including 12 weeks post-conversion into boards. Boards were used to make a nested stack arrangement allowing plastic tanks top be placed in the centre. The tanks contained a sub-sample of the full-size boards in order to investigate insect activity and effects of gammairradiation. A total of 115 insect species representing 16 of the 34 British orders were collected during the trials. Seventy-two percent of these insects were collected from within the stacks of lumber and investigations using sealed tanks containing boards showed that the insects could influence the fungal colonisation of sawn lumber. Despite the relatively short length of the trials, a succession of insect colonisation from fungivores through to predators and detritivores was recorded. Boards, which were sterilised by gamma-irradiation, were preferentially colonised by mould fungi and subsequent internal staining was confined to the outer surface. Trials with short-length billets allowed the wood-colonising ability of selected sapstain fungi to be investigated under controlled conditions following sterilisation by gamma-irradiation or autoclaving, and storage at 30°C and 20°C. Lesion formation in gamma-irradiated tissue was solely due to the fungus potentially conditioning the wood for colonisation. Colonisation studies also revealed that different fungi exhibit different strategies enabling them to infect timber. Pathogenic species demonstrated a relatively fast initial growth rate to establish themselves before triggering any host anti-fungal responses in the wood. The characteristic lesions created in the billets were investigated using light and electron microscopy to reveal hyphal invasion and or/ wood cell modifications. Respiratory activity of the lesions was elucidated using radioactively labelled glucose allowing the metabolic pathways to be ascertained and demonstrated that wood tissue in the apparently healthy regions adjacent to the lesions reacted as if infected. Future work considers the possibility of biocontrol, using insects in combination with gamma-irradiation of sawn lumber and also further investigations into the reaction zones produced by the fungus growing in the wood.
11
Lydersen, Stian. "Reliability testing based on deterioration measurements." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for matematiske fag, 1988. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24391.
Full textAbstract:
In traditional reliability life testing and accelerated life testing, usally only the failure mode and the lifetime upon failure or censoring, are recorded. The information obtained from such testing may be signicantly improved by aslo recording one or more measures of deterioration, such as wear depth, crack length, leakage rate, etc. Failure occurs when a measure of deterioration, or a combination of them, reach a critical value. This approach calls for refined reliability models and estimation techniqes. Established derministic models for some physical deterioration mechanisms are described. Alternative appraches for stochastic models are studied, such as cumulative stochastic processes, regression models with random cofficients, Wiener processes with random drift, and the Bernstein distribution and related models. Special attention is attached to models where a parameter set in the stochastic process is considered as a stochastic variable with one realization per specimen. Maximum likelihood estimatiors are studied and compared for the Wiener process model, and the Wiener process with random drift.
12
Venkatasamy, R. "Mechanisms of bacterial deterioration of wood." Thesis, University of Portsmouth, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234521.
Full text
13
Ercisli, Safak. "Development of Enhanced Pavement Deterioration Curves." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56599.
Full textAbstract:
Modeling pavement deterioration and predicting the pavement performance is crucial for optimum pavement network management. Currently only a few models exist that incorporate the structural capacity of the pavements into deterioration modeling. This thesis develops pavement deterioration models that take into account, along with the age of the pavement, the pavement structural condition expressed in terms of the Modified Structural Index (MSI). The research found MSI to be a significant input parameter that affects the rate of deterioration of a pavement section by using the Akaike Information Criterion (AIC). The AIC method suggests that a model that includes the MSI is at least 10^21 times more likely to be closer to the true model than a model that does not include the MSI. The developed models display the average deterioration of pavement sections for specific ages and MSI values.
Virginia Department of Transportation (VDOT) annually collects pavement condition data on road sections with various lengths. Due to the nature of data collection practices, many biased measurements or influential outliers exist in this data. Upon the investigation of data quality and characteristics, the models were built based on filtered and cleansed data. Following the regression models, an empirical Bayesian approach was employed to reduce the variance between observed and predicted conditions and to deliver a more accurate prediction model.Master of Science
14
Morcous, George. "Case-based reasoning for modeling bridge deterioration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0011/NQ59227.pdf.
Full text
15
De, Almeida Rodrigues Andreia. "Concrete deterioration due to sulfide-bearing aggregates." Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26812.
Full textAbstract:
Dans la région de Trois-Rivières (Québec, Canada), plus de 1 000 bâtiments résidentiels et commerciaux montrent de graves problèmes de détérioration du béton. Les problèmes de détérioration sont liés à l'oxydation des sulfures de fer incorporés dans le granulat utilisé pour la confection du béton. Ce projet de doctorat vise à mieux comprendre les mécanismes responsables de la détérioration de béton incorporant des granulats contenant des sulfures de fer, et ce afin de développer une méthodologie pour évaluer efficacement la réactivité potentielle de ce type de granulats. Un examen pétrographique détaillé de carottes de béton extraites de fondations résidentielles montrant différents degré d’endommagement a été réalisé. Le granulat problématique contenant des sulfures de fer a été identifié comme un gabbro à hypersthène incorporant différentes proportions (selon les différentes localisations dans les deux carrières d’origine) de pyrrhotite, pyrite, chalcopyrite et pentlandite. Les produits de réaction secondaires observés dans les échantillons dégradés comprennent des formes minérales de "rouille", gypse, ettringite et thaumasite. Ces observations ont permis de déterminer qu’en présence d'eau et d'oxygène, la pyrrhotite s’oxyde pour former des oxyhydroxides de fer et de l'acide sulfurique qui provoquent une attaque aux sulfates dans le béton. Tout d'abord, la fiabilité de l'approche chimique proposée dans la norme européenne NF EN 12 620, qui consiste à mesurer la teneur en soufre total (ST, % en masse) dans le granulat pour détecter la présence (ou non) de sulfures de fer, a été évaluée de façon critique. Environ 50% (21/43) des granulats testés, représentant une variété de types de roches/lithologies, a montré une ST > 0,10%, montrant qu'une proportion importante de types de roches ne contient pas une quantité notable de sulfure, qui, pour la plupart d’entre eux, sont susceptibles d'être inoffensifs dans le béton. Ces types de roches/granulats nécessiteraient toutefois d'autres tests pour identifier la présence potentielle de pyrrhotite compte tenu de la limite de ST de 0,10 % proposée dans les normes européennes. Basé sur une revue exhaustive de la littérature et de nombreuses analyses de laboratoire, un test accéléré d’expansion sur barres de mortier divisé en deux phases a ensuite été développé pour reproduire, en laboratoire, les mécanismes de détérioration observés à Trois-Rivières. Le test consiste en un conditionnement de 90 jours à 80°C/80% RH, avec 2 cycles de mouillage de trois heures chacun, par semaine, dans une solution d’hypochlorite de sodium (eau de javel) à 6% (Phase I), suivi d’une période pouvant atteindre 90 jours de conditionnement à 4°C/100 % HR (Phase II). Les granulats ayant un potentiel d'oxydation ont présenté une expansion de 0,10 % au cours de la Phase I, tandis que la formation potentielle de thaumasite est détectée par le regain rapide de l'expansion suivi par la destruction des échantillons durant la Phase II. Un test de consommation d'oxygène a également été modifié à partir d’un test de Drainage Minier Acide, afin d'évaluer quantitativement le potentiel d'oxydation des sulfures de fer incorporés dans les granulats à béton. Cette technique mesure le taux de consommation d'oxygène dans la partie supérieure d'un cylindre fermé contenant une couche de matériau compacté afin de déterminer son potentiel d'oxydation. Des paramètres optimisés pour évaluer le potentiel d'oxydation des granulats comprennent une taille de particule inférieure à 150 μm, saturation à 40 %, un rapport de 10 cm d'épaisseur de granulat par 10 cm de dégagement et trois heures d’essai à 22ᵒC. Les résultats obtenus montrent que le test est capable de discriminer les granulats contenant des sulfures de fer des granulats de contrôle (sans sulfures de fer) avec un seuil limite fixé à 5% d'oxygène consommé. Finalement, un protocole d'évaluation capable d’estimer les effets néfastes potentiels des granulats à béton incorporant des sulfures de fer a été proposé. Le protocole est divisé en 3 grandes phases: (1) mesure de la teneur en soufre total, (2) évaluation de la consommation d'oxygène, et (3) un test accéléré d’expansion sur barres de mortier. Des limites provisoires sont proposées pour chaque phase du protocole, qui doivent être encore validées par la mise à l’essai d'un plus large éventail de granulats.In the Trois-Rivières area (Quebec, Canada), more than 1 000 houses and commercial buildings are showing serious concrete deterioration problems. The deterioration problems are related to the oxidation of sulfide-bearing aggregates used for concrete manufacturing. This PhD project aims to better understand the mechanisms responsible for the deterioration of concrete incorporating sulfide-bearing aggregates in order to develop a methodology to efficiently evaluate the potential reactivity of such types of aggregates. A detailed petrographic examination of core samples extracted from concrete house foundations showing various degrees of severity was carried out. The problematic aggregate was identified as an hypersthene’s gabbro incorporating various proportions (according to different locations in the two originating quarries) of pyrrhotite, pyrite, chalcopyrite and pentlandite. Secondary reaction products observed in degraded core samples include “rust” mineral forms, gypsum, ettringite and thaumasite. For those observations, it was concluded that, in presence of water and oxygen, pyrrhotite oxidizes to form iron oxyhydroxides and sulfuric acid that provokes a sulfate attack in concrete. First, the reliability of the chemical approach proposed in the European Standards NF EN 12 620, which consists in the measurement of the total sulfur content (ST, % by mass) in the aggregate to detect the presence (or not) of iron sulfide minerals, was critically evaluated. About 50% (21/43) of the aggregate materials tested, representing a variety of rock types / lithologies, showed a ST > 0.10%, showing that a significant proportion of rock types does contain a noticeable amount of sulfide, which for most of them, are likely to be innocuous in concrete. Such rock types / aggregates would however require further testing to identify the potential presence of pyrrhotite considering the ST limit of 0.10% proposed in European standards. Based on extensive literature reviews and laboratory investigations, a two-phase accelerated mortar bar expansion test was then developed to reproduce, in the laboratory, the deterioration mechanisms observed on site. The test consists in 90 days of storage at 80°C/80% RH, with 2 three-hour wetting cycles per week in a 6% sodium hypochlorite (bleach) solution (Phase I) followed by up to 90 days of storage at 4°C/100% RH (Phase II). Aggregates with oxidation potential presented an expansion over 0.10% during Phase 1, while thaumasite formation potential is detected by rapid regain of expansion followed by destruction of the samples during Phase II. Also, an oxygen consumption test was modified from research carried out in the context of acid rock drainage, to quantitatively assess the sulfide oxidation potential of concrete aggregates. The technique measures the oxygen consumption rate at the top of a closed cylinder containing a layer of compacted material to determine its oxidation potential. Optimized testing parameters include an aggregate particle size inferior to 150 μm at 40% saturation, a ratio of 10 cm of aggregate material thickness for 10 cm headspace and 3 hours testing at 22ᵒC. The results thus obtained showed that the test is able to discriminate the aggregates containing iron sulfide minerals from the control aggregates with a threshold limit fixed at 5% oxygen consumed. Finally, an assessment protocol was proposed to evaluate the potential deleterious effects of iron sulfide bearing aggregates when used in concrete. The protocol is divided into 3 major phases: (1) total sulfur content measurement, (2) oxygen consumption evaluation, and (3) an accelerated mortar bar expansion test. Tentative limits are proposed for each phase of the protocol, which still need to be validated through the testing of a wider range of aggregates.
16
Astruc, Salud. "A prevention of significant deterioration case study." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09052009-040712/.
Full text
17
Thorpe, G. Leigh. "Identifying and predicting deterioration during psychotherapeutic interventions." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2160/.
Full textAbstract:
The literature review critically evaluated research articles focusing on deterioration in psychotherapy published since a watershed review by Mohr (1995). This review adopted the recommendations made by Mohr (1995) as a framework for the literature. A total of 28 studies were identified and reviewed using a quality rating system derived from Mohr's recommendations according to the extent to which these recommendations were implemented in the identified studies. The review yielded a higher average rate of deterioration (9-17%) in comparison with Mohr's review (5-10%). It was concluded that research into deterioration generally has continued to suffer from methodological limitations. The intention of the research report was to investigate the phenomena of overall deterioration and sudden deterioration in a routinely collected data set collected from the Improving Access to Psychological Therapies (IAPT) initiative. Sudden deterioration was explored to determine whether it existed and how it may be defined. The rates of deterioration within the IAPT data were identified, and predictors of these were assessed. It was determined that an appropriate definition for sudden deterioration was a reliable between-session change using the Patient Health Questionnaire-9; PHQ-9), that was not allied to sudden gains. Rates of sudden deterioration and overall deterioration were found to be 3.4% and 3.1% respectively. It was concluded that sudden deterioration exists as a phenomenon, is closely related to overall deterioration and that rates of deterioration in the IAPT dataset were relatively low.
18
SILVA, Rodrigo Bernardo da. "A Bayesian approach for modeling stochastic deterioration." Universidade Federal de Pernambuco, 2010. https://repositorio.ufpe.br/handle/123456789/5610.
Full textAbstract:
Made available in DSpace on 2014-06-12T17:40:37Z (GMT). No. of bitstreams: 2
arquivo720_1.pdf: 2087569 bytes, checksum: 4e440439e51674690e086dbc501c7a58 (MD5)
license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5)
Previous issue date: 2010Conselho Nacional de Desenvolvimento Científico e Tecnológico
A modelagem de deterioracão tem estado na vanguarda das analises Bayesianas de confiabilidade. As abordagens mais conhecidas encontradas na literatura para este proposito avaliam o comportamento da medida de confiabilidade ao longo do tempo a luz dos dados empiricos, apenas. No contexto de engenharia de confiabilidade, essas abordagens têm aplicabilidade limitada uma vez que frequentemente lida-se com situacões caracterizadas pela escassez de dados empiricos. Inspirado em estrategias Bayesianas que agregam dados empiricos e opiniões de especialistas na modelagem de medidas de confiabilidade não-dependentes do tempo, este trabalho propõe uma metodologia para lidar com confiabilidade dependente do tempo. A metodologia proposta encapsula conhecidas abordagens Bayesianas, como metodos Bayesianos para combinar dados empiricos e opiniões de especialistas e modelos Bayesianos indexados no tempo, promovendo melhorias sobre eles a fim de encontrar um modelo mais realista para descrever o processo de deterioracão de um determinado componente ou sistema. Os casos a serem discutidos são os tipicamente encontrados na pratica de confiabilidade (por meio de simulacão): avaliacão dos dados sobre tempo de execucão para taxas de falha e a quantidade de deterioracão, dados com base na demanda para probabilidade de falha; e opiniões de especialistas para analise da taxa de falha, quantidade de deterioracão e probabilidade de falha. Estes estudos de caso mostram que o uso de informacões especializadas pode levar a uma reducão da incerteza sobre distribuicões de medidas de confiabilidade, especialmente em situacões em que poucas ou nenhuma falha e observada.
19
Dimitriadi, Rafaela. "Willy Loman's Deterioration : From a Psychoanalytical Perspective." Thesis, Högskolan i Gävle, Avdelningen för humaniora, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-29706.
Full textAbstract:
This essay will analyze the protagonist of Arthur Miller’s, Death of a Salesman, Willy Loman, from a psychoanalytical perspective. The purpose is to establish the reason for his suicide. The thesis is that Willy Loman seems to have developed a narcissistic and borderline personality disorder and as a consequence his mentality was affected and that led him to commit suicide. Willy Loman is a self-centered man who has an obsession with success both as a salesman but also as a husband and a father, in such a way that his mental health is questioned. This suggests that his final decision to commit suicide has been affected by some type of mental disorder that derives from his neuroses. Therefore, Willy Loman’s behavior will be investigated by using Freud’s psychoanalytical theory of neuroses and mental disorders.
20
O'Leary, Jessica A. "Recognising paediatric deterioration in a simulated environment." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/84892/1/Jessica_O%27Leary_Thesis.pdf.
Full textAbstract:
This thesis examined the impact of high fidelity patient simulation on paediatric critical care nurses' self-efficacy and knowledge for recognising and responding to paediatric deterioration. This research highlights the positive effect simulation education can have on nursing learning outcomes which may influence patient safety through the timely recognition and management of the deteriorating child.
21
CASARI, Nicola. "Modeling approaches for gas turbine deterioration analysis." Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2478784.
Full textAbstract:
Nonostante le turbine a gas siano una comune fonte di energia sia per applicazioni
stazionarie che per il campo aeronautico, l’effetto della presenza di particolato nell’aria
processata `e un aspetto che `e stato spesso sottostimato nella letteratura. Le particelle
presenti nell’aria possono risultare, a seguito dell’impatto con le superfici bagnate dal
flusso, in una variazione di geometria e comportare una riduzione delle performance o
piuttosto della vita utile della macchina. Sabbia o, in generale, altri tipi di contaminant
possono causare erosione o deposizione sia nelle sezioni fredde (compressore) che calde
(turbina) della macchina.
Questo problema si verifica tipicamente per turbine a gas stazionarie che lavorano in
ambienti ostili, aventi alta concentrazione di particolato nell’aria: in tali casi, il problema
pu`o essere solo mitigato, ma non completamente evitato, dall’installazione di sistemi
di filtrazione all’aspirazione della macchina. Tali filtri non vengono invece utilizzati in
caso di turbomacchine per la propulsione aeronautica. Perci`o, a seguito di tempeste
di sabbia o eruzioni vulcaniche, possono essere presenti particelle all’altezza di crociera.
In alternativa, il decollo, l’atterragio o il volo a bassa quota in localit`a remote possono
rappresentare un’ulteriore rischio per l’ingestione di particelle.
Un’analisi completa di tutti gli aspetti del deterioramento delle turbine a gas e della
loro modellazione numerica, tenendo in considerazione erosione, formazione del deposito
ed evoluzione del deposito nel tempo non `e ancora stata presentata in letteratura. In
questo lavoro viene presentata la modellazione di tutti questi meccanismi, di entrambe
le sezioni della macchina. In particolare, per tutti i fenomeni analizzati, il processo di
contaminazione delle pale `e basato sullo studio numerico tramite CFD (Computational
Fluid Dynamics), con un approccio Euleriano-Lagrangiano. La traiettoria delle particelle
`e calcolata considerando il contributo stocastico derivante dalla turbolenza del moto.
Con tale approccio possono essere considerati sia il tracciamento transitorio che quello
stazionario: entrambi i metodi saranno utilizzati e la scelta dell’uno piuttosto che dell’altro
verr`a giustificata in base al tempo caratteristico del fenomeno che si sta considerando.
Infatti la decisione sar`a basata sul confronto del tempo caratteristico del fenomeno di
erosione/deposizione con quello relativo alla rapidit`a con cui si manifesta il degrado delle
prestazioni a livello di macchina.
La modifica delle condizioni al contorno del dominio e, in particolare, delle pareti interessate dall’impatto di particelle costituisce il passaggio fondamentale per rappresentare
il loro effetto. L’implementazione presentata in questo lavoro `e stata ottenuta mediante
due diversi approcci: mesh mobili (moving mesh) e una serie di tecniche innovative che
verranno prersentate nel seguito.
Da questo lavoro possono essere ottenute alcune informazioni importanti riguardo le aree che sono maggiormente affette dalla presenza di particelle. Inoltre alcune tecniche che
possono essere usate per la valutazione dell’effetto dell’interazione parete-particella vengono illustrate. Infine viene presentata un’analisi non-dimensionale del comportamento
della particella all’impatto, suggerendo come pu`o essere realizzata una mappa universale
per la classificazione delle conseguenze di tale impatto. Dalle considerazioni e dai modelli
sviluppati, viene infine proposta una metodologia preliminare per la progettazione della
pala in condizioni di presenza di particelle.Gas turbines are a popular source of power for aerospace and land-based applications. Nevertheless the importance of particle ingestion and its implication is an often underestimated problem which can lead to the variation of geometry of aerodynamic surfaces, entailing performance degradation and, possibly, a reduction in engine life. The presence of sand and other type of particles can cause erosion or deposition in both the compressor and turbine sections. This problem can occur for land based turbines operating in harsh environment, where the problem can be mitigated (but not eliminated) by installing filtration systems. For what concern the aerospace field, filtration systems cannot be used. Volcanic eruptions and sand dust storms can send particulate to aircraft cruising altitudes. Also, aircraft operating in remote locations or at low altitude can be subjected to particle ingestion, especially in desert environments. A thorough analysis of the deterioration mechanisms of gas turbines, and of their modelling, including erosion, deposit formation and deposit evolution over time has not been presented in the literature so far. In this work, the modelling of all such mechanisms has been performed for both the hot and the cold section. In all the presented approaches, the blade contamination process analysis is based on the Computational Fluid Dynamics (CFD) study, with a Eulerian-Lagrangian approach. The stochastic particle tracking for the trajectory computation has been employed. With this approach, both the transient and the steady state tracking can be performed, and both the methods will be employed: the choice of the time treatment will be made by comparing the time scale of the deposition/erosion phenomena to the time scale of the performance degradation. The boundary variation as a consequence of the particle impact has been implemented, either with a mesh morphing approach or innovative techniques that are proposed to include the particle impact consequences on the flow field. The displacement of the boundary, or the variation of some of its characteristics (e.g. roughness), represents the most important effect of the deposit/erosion and, therefore, particular care should be taken when dealing with it. From this work, some important information regarding the areas which are affected the most by the particles ingestion can be retrieved and the techniques that can be employed for the evaluation of the effects of the particle-wall interaction are explained. Indeed, Thanks to the model here proposed, a preliminary methodology for the robust design under fouling conditions is proposed. Eventually a non-dimensional analysis of the behaviour of particles upon impact is proposed, suggesting that a universal map for the classification of the consequences of the impingement can be outlined. Such map is proposed as a tool for the detection of the effect of the impact. Eventually, starting from the considerations and the models developed, a design-for-fouling oriented optimization is proposed.
22
LeBoeuf, Leighton Lee Jr. "Investigation of rabid low temperature depolymerization of polyethylene terephthalate : a novel approach." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/8588.
Full text
23
Ondrásik, Martin. "Some thermodynamics of pore water in rock deterioration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ30923.pdf.
Full text
24
Habel, Simon G. "An assessment of Heysen Trail wear and deterioration /." Title page, table of contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09ENV/09envh113.pdf.
Full text
25
Singh, Grewal M. "Gas Turbine Engine Performance Deterioration Modelling and Analysis." Thesis, Cranfield University, 1988. http://dspace.lib.cranfield.ac.uk/handle/1826/8068.
Full textAbstract:
In-service performance deterioration of gas turbine engines
can be identified, at the engine module level, in terms of
reductions in the component mass flow and the efficiency.
Continued operation of a deteriorated gas turbine is (i)
uneconomical and (ii) unsafe. Timely identification of the
faults and ensuing maintenance could prevent both. Gas Path
Analysis is a technique to establish the current performance
level of the gas turbines and identify the faulty modules.
Computer models can predict the off_design performance of gas
turbines by aero-thermo-dynamically matching the engine
components. This thesis describes the development of DETEM
(DEeteriorated Turbine Engine Model), a generalised computer
program, developed to model degraded gas turbine engines and
analyse faults.
The program has an integrated graphics module and creates
windows on the VDU terminal,for displaying the program output
and accepting the user input. This enables the user to compare
the results of two different types of runs at the same time.
The program incorporates sensor models that modify the output,
with noise and in bias, based on the sensor characteristics,
thus simulating a real engine. It is possible to simulate the
engine performance at design point, off-design and under
transient conditions. The runs could be for a "clean" and a
deteriorated engine.
Three techniques, iterative, fault coefficient matrix, and
a statistical best-estimation technique, have been used to
analyse the engine performance and identify the fault.
Analysis of two and three shaft turbo-shaft engines and two
spool turbo-fan and turbo-jet engines have been worked out in
the thesis. Effects of reducing the number of measurements and
measuring different engine parameters, on the accuracy of the
fault identification, have been studied.
The program is considered to have a potential for the
generation of fault trees for rule-based expert system
applied to gas turbine diagnostics. Because of the controlled
output to the screen, a direct comparison of two different
runs side by side, on the same screen, makes the program a
good teaching aid for gas turbine diagnostics.
26
Griffin, Isobel Margaret. "Deterioration mechanisms of historic cement renders and concrete." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8104.
Full textAbstract:
Since the introduction of Portland cement in the early nineteenth century the number of buildings constructed from concrete or using cement mortars and renders has grown exponentially, and cement is one of the most common building materials in use today. Consequently a significant proportion of the built heritage contains cementitious materials. The relative youth of these buildings means that less research has been undertaken to understand how and why they deteriorate than for traditional buildings, and that the development of appropriate conservation methods and techniques is less advanced. The primary aim of this research was to understand the causes and mechanisms of some of the types of deterioration commonly found in historic concrete and cement buildings and structures, with reference to the Second World War reinforced concrete and cement-rendered buildings at East Fortune airfield in East Lothian, Scotland. Additional aims were to investigate the efficacy of the building repairs and maintenance regimes undertaken to date, and to make recommendations for the future conservation of the buildings. East Fortune airfield contains a number of cement-rendered brick masonry buildings and a reinforced concrete air raid shelter. The initial visual survey identified several types of deterioration, from which the blistering and flaking of the render; the cracking and delamination of the render; and the spalling of the concrete in the air raid shelter were selected for further research. The research included time lapse photography, non-destructive testing, environmental monitoring and the physical, chemical and petrographic characterisation of the building materials. Hypotheses regarding the causes of deterioration were tested in the laboratory, for example with linear variable displacement transducer measurements, and modelled using crack propagation theories and models for water transport through porous media. It is demonstrated that the blistering and flaking of the render is caused by shale aggregate particles, which undergo sufficient expansion during freeze-thaw cycles to crack the surrounding render. This phenomenon is termed ‘pop-outs’ in the concrete literature. The more catastrophic cracking and delamination of the renders is also due to freeze-thaw cycling, which is shown to cause significant damage provided the moisture content of the render is above a certain threshold level. This type of deterioration has occurred at an accelerated rate for some of the modern render repairs, due to an inadequate understanding of the properties of the original and repair materials. In particular, the properties of the bricks are critical to the performance of the cement renders, and it is found that the sorptivity of historic bricks may vary considerably depending upon the orientation of the brick. Finally, the diagnosis for the air raid shelter is that the corrosion of the steel reinforcements is caused by high levels of chlorides present within the raw materials used to make the pre-cast concrete sections. The results of the investigations are used to suggest building conservation solutions for this particular site. Furthermore, since the deterioration mechanisms investigated are common for historic cement and concrete, the findings are relevant to many other sites. The over-arching methodology used to investigate the deterioration at the site and the methodologies developed to test particular hypotheses are also applicable for other investigations of historic building materials. There is much about this research that is innovative and new. The work on render cracking compares the results of dilation tests on cementitious and ceramic materials, which has not been done previously, and the pop-outs diagnosed in the work on render flaking have rarely, if ever, been reported for cement renders. The modelling work undertaken to quantify the stresses produced by the pop-outs and to explain the inclined crack formation patterns is entirely original. The use of petrography to diagnose causes of render failure is described in the literature, but this is one of very few case studies to be written up, and the work on the air raid shelter constitutes the only formal investigation of this type of Stanton shelter.
27
Luxton, William Booth. "The exposure and deterioration of granitic building stone." Thesis, Middlesex University, 1997. http://eprints.mdx.ac.uk/10167/.
Full textAbstract:
The study of building stone decay is a field of increasing impOliance. Many previous studies have focused on limestone, and recently on sandstone. These studies can provide information on the spatial and temporal distribution of weathering forms and the degree of impact of polluted urban atmospheres. Several of these schemes rely on subjective visual appraisal by the examiner, which is unreliable and prone to measurement error. To counter these problems, and address the relative paucity of studies on granitic building stone, a novel semi-quantitative measure of rock quality was created. The creation of the Stone Deterioration Index (SDI) allowed the evaluation of longterm granitic building stone decay, while the short-term response of fresh granite to atmospheric exposure was examined through the use of microcatchment units (MCV' s). The measurement of run-off water and the physical response of fresh granite over a 91 week exposure period at three sites of varying pollution concentrations, allowed an assessment of the relative importance of surface roughness, composition and, dry & total deposition on deterioration rates. The exposure programme used MCV's containing granodiorite slabs with different degrees of surface roughness (finish) to collect run-off. This was measured for volume, pH, conductivity, and selected anion and metal concentrations. Run-off concentrations were measured by a Dionex 2000i ion chromatograph and a Perkin-Elmer ICP 40 inductively coupled plasma spectrometer respectively.Site was the most important factor in determining run-off concentrations showing significant variations between the urban and rural sites. Surprisingly, MCl) composition and surface roughness variations had little influence on component concentrations, and there were no systematic significant inter-finish variations. The MCV slabs showed no significant changes in weight, surface roughness or composition as a result of exposure. Granitic carousel tablets of varying composition, designed to assess the relative influence of dry and total deposition on granitic deterioration, also showed no systematic effects from exposure. The lack of significant variation between the pre- and post-exposure characteristics of the MCV slabs and carousel tablets could indicate that exposure length was not sufficient to generate measurable decay features. The assessment of long-term decay rates by the SDI, which was non-destructive and applied in situ, involved the measurement and rating of four parameters (surface strength, surface roughness, surface coatings and discolouration), to form a semi-quantifiable measure of rock quality. Eleven churches in Dartmoor, built between 1430AD-1896AD, were assessed by the SDI to provide a measure of long-term deterioration rates. Cross-church comparisons revealed no consistent effects on deterioration rates with increasing stone height. Aspect, however, did playa major role in influencing deterioration rates. The south facing walls (mean: 60 SDI points) showed the least amount of decay and had the slowest deterioration rate, while west (mean: 56 SDI) and north facing walls (mean: 53 SDI) deteriorated 6% and 14% faster than south facing walls respectively. Results suggest biological weathering was the major process in granite building stone deterioration in the Dartmoor region. These findings correspond to research by Robinson and Williams (1996) on sandstone churches. They ranked aspect by weathering scores derived from visual assessment of individual stone block, and found deterioration features were strongly affected by aspect, in the order; East>North>West>South. Although there is convergence in the decay pattern between aspects for the two stone types, the SDI index was formulated for coarse-grained igneous rocks, where it shows a strong statistical relationship between building age and rock quality (1=0.74). This allowed the formulation of an average linear deterioration rate for granite buildings in a clean, rural environment of 4.59 SDI points per hundred years.
28
RUNGTHONGBAISUREE, Somkiat. "FUNDAMENTAL INVESTIGATIONS ON CORROSION DETERIORATION OF STEEL STRUCTURES." Kyoto University, 1991. http://hdl.handle.net/2433/138450.
Full text
29
Johansson, Anna. "Air pollution and paper deterioration : causes and remedies /." Göteborg : Göteborg university, Department of chemistry, 2000. http://catalogue.bnf.fr/ark:/12148/cb376268384.
Full text
30
Nicholson, Dawn Theresa. "Deterioration of excavated rockslopes : mechanisms, morphology and assessment." Thesis, University of Leeds, 2000. http://etheses.whiterose.ac.uk/334/.
Full textAbstract:
Results are reported of laboratory simulated weathering processes on a range of sedimentary rocks and the investigation of the deterioration of rock masses as observed on engineered and quarried rockslopes. The simulated weathering processes include freeze-thaw, wetting and drying, salt weathering and slaking. It is found that the rock properties of pore volume, saturation coefficient and microporosity exert greatest influence on susceptibility to breakdown. For stronger rocks it is found that durability correlates well with high strength and elasticity. A range of rock flaws visible in hand specimen are described and their influence on rock deterioration assessed. Linear flaws such as laminations and stylolites are more likely to be associated with breakdown, and the role of structural weaknesses is most evident in stronger rocks. Rock breakdown mode due to experimental weathering is found to closely resemble material weathering of source slopes in the field. A range of rock breakdown mechanisms are inferred from changes in pore microstructure and rock strength. There are indications of a progression from deterioration which is invisible and involves modification of the existing pore structure, to macro deterioration resulting from generation of new void space and microcracks. After field investigation of more than two hundred rockslopes deterioration is found to be widespread, and there is little evidence of a systematic approach to its assessment or mitigation. Fracture spacing, rock strength and lithology are found to be the most influential factors in rockslope deterioration and these are used to define a characteristic range of rock mass types. A range of morphological forms attributed to deterioration are defined and described. An engineering classification of deterioration modes is presented, based on constituent material size, velocity of movement and frequency of occurrence. Deterioration modes correlate well with rock mass type. A new rock mass classification, called Rockslope Deterioration Assessment (RDA) is proposed, dealing specifically with shallow, weathering and erosion-related rockslope processes. RDA is divided into three stages; a ratings assessment of deterioration risk, a qualitative review of the likely deterioration hazard, and guidance on appropriate mitigation. The findings of the experimental work are incorporated into stage one of RDA where appropriate. Notable in this respect is the emphasis in RDA on evaluation of fracture spacing on the basis of all fractures present, whether open or incipient, and whether natural, or induced by blasting, weathering or stress release. RDA is applied to the slopes investigated in the fieldwork and shows that certain types of rock mass are associated with higher risk of failure. There is also an element of predictability in the occurrence of deterioration modes. Correlation between stage one of RDA and Rock Mass Rating is examined and it is shown that, although there are some similarities, a fundamental difference relates to the basis upon which fracture spacing is assessed.
31
Sultana, Masuda. "Assessment and Modelling Deterioration of Flood Affected Pavements." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/367367.
Full textAbstract:
The efficiency of the road management system is increasingly challenged due to the frequent occurrences of extreme weather events, such as intense heavy rainfall, cyclones and flooding. The unpredictable events such as Hurricanes Katrina and Rita in the USA (2005), extreme flooding in January 2011 in South-East Queensland, Cyclones Oswald (2013) and Marcia (2015) in Queensland had severe impacts upon the road infrastructure. These roads are now subject to a wider range of climatic conditions over their service life than was originally anticipated during their design. To date, no deterioration model can accurately predict the impact of floods on pavements. To understand the impact of January 2011 flood on the structural performance of flood affected pavements, Falling Weight Deflectometer (FWD) deflection data and surface condition data (rutting and roughness), on flood-affected roads managed by Brisbane City Council, Department of Transport and Main Roads (TMR), Queensland and Roads and Maritime Services, New South Wales (RMS, NSW), Australia, were collected and examined.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text
32
Cox, Diane Marie 1968. "Category and attribute knowledge deterioration in Alzheimer's Disease." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278124.
Full textAbstract:
Changes associated with Alzheimer's Disease (AD) in the association cortices of temporal, occipital, and parietal lobes of the brain, result in significantly impaired performance of AD subjects on tests of semantic memory. The most prevalent theory regarding the deterioration of semantic memory is that it is a bottom-up process. That is, the knowledge of attributes becomes lost or inaccessible prior to the knowledge of categories. Previous research of this theory has resulted in conflicting results. The purpose of this study was to test further the theory, while taking into account task difficulty. Thirty probable AD and 28 normal elderly subjects were administered tasks of attribute and categorical knowledge. Results revealed significant differences in performance as a result of task difficulty. These results call into question the methodology previously used to assess the bottom-up theory, as well as the ability to use attribute and categorical knowledge separately.
33
Harris, Norma Patricia. "Preparing Novice Nurses for Early Recognition Acute Deterioration." ScholarWorks, 2018. https://scholarworks.waldenu.edu/dissertations/6039.
Full textAbstract:
Hospitalized patients increasingly present with complex health issues that place them at risk for acute patient deterioration (APD). Novice nurses are ill-equipped with the critical clinical skills to function competently in recognizing APD, placing patients at risk for negative health outcomes. This project addressed the need to educate novice nurses to recognize APD and answered the project focused questions that asked if an educational intervention with high-fidelity simulation (HFS) would improve nurse knowledge and clinical confidence in recognizing APD. Benner's novice-to-expert and the constructivism theory were used to guide the project. Based upon a review of the literature, the HFS was developed to provide scenarios in which participants would view APD evolving case studies and demonstrate knowledge and skill for caring for patients with APD. A convenience sample of 11 novice nurses participated in the pre- and posttest design project to determine if knowledge and clinical competence increased. Data from the HFS program were analyzed; results showed no statistically significant change in knowledge or confidence post intervention (p = 0.441). A larger sample size is recommended for future HFS interventions at the site to determine if the program of education will increase knowledge and clinical confidence with future iterations of HFS. The project has the potential to promote positive social change as novice nurses learn to recognize and respond to APD and as APD events are reduced.
34
Won, Chee-Youb. "Depolymerization of nylon 6,6 in the presence of phase transfer catalyst." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/8707.
Full text
35
Argyropoulos, Dimitris S. "Synthesis and degradation of model network polymers." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72032.
Full textAbstract:
Theoretical expressions essentially based on the Flory-Stockmayer statistics of gelation were experimentally examined for their applicability beyond the gel point. By studying the crosslinking process of a polyester network formed from 1,3,5-benzenetriacetic acid and 1,10-decamethylene glycol beyond the gel point, the validity of the expressions was quantitatively confirmed, and their limitations were delineated.On stepwise degradation of a similar network, increasingly large soluble fractions were obtained at each step, and their weight-average molecular weights increased as the degelation point was approached. The molecular weights and distributions of these fractions were in close quantitative agreement with theory, i.e., they represented a near-mirror image of the molecular weights of sol fractions obtained on crosslinking beyond the gel point. Similar results were obtained by degrading a network prepared by the random crosslinking of monodisperse primary chains of polystyrene.
Experimental support was thus obtained for treating random network degradation by reversing the statistics of the Flory-Stockmayer theory of gelation.
36
Asiedu, Ernest Assah. "The response of cowpea (Vigna unguiculata L. Walp) seeds differing in seed coat colour to storage and reduced water availability during germination." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU482662.
Full textAbstract:
These studies were conducted to determine the response of cowpea cultivars differing in seed coat colour to storage and reduced water availability during germination, and to relate these to the chemical composition of their seed coats. Seeds of five cowpea cultivars were stored under simulated tropical conditions (30°C/75.5% r.h.) for 6 months, subjected to accelerated ageing (40°C/100% r.h.) for 6 days or controlled deterioration (40°C/20% m.c.) for 4 days. Unpigmented seeds showed more rapid deterioration which was revealed by low germinations, high leachate conductivity and poor vital staining with 2, 3, 5 Triphenyl Tetrazolium Chloride (TTC). These differences were attributed to differences in moisture contents that occurred in storage as well as genotypic differences. Increased susceptibility to imbibition damage occurred during storage particularly in unpigmented seeds. The seed vigour parameters at the end of the stimulated tropical storage correlated well with accelerated ageing, suggesting the possible use of rapid ageing to predict the storage potential of cowpea seeds. Percentage radicle emergence was high in the pigmented cultivars germinated at -0.0015, -0.1 and -0.15 MPa and lower in unpigmented cultivars as matric potential was reduced. Imposition of reduced water availability (-0.15 Mpa) after 12, 24 and 48 hours germination at -0.0015 MPa led to slower rates of radicle emergence in all seeds transferred at 12 and 24 hours. In the unpigmented cultivars, these early transfers led to reduced radicle emergence after 7 days and low final normal germination after transfer to -0.0015 MPa for a further 7 days. This deleterious effect was revealed by poor vital staining of the embryonic axes. Protein synthesis of root tips after 24 hours -0.0015 MPa, 96 hours -0.15 MPa followed by a recovery period of 48 hours -0.0015 MPa was twice as much in the pigmented cultivar which explained its greater ability to recover from stress. Screening of a further ten cultivars for tolerance of reduced water availability revealed three groupings, (1) unpigmented cultivars that showed low final normal germination and rapid rates of water uptake in water, (2) smooth-coated pigmented cultivars that showed high final germination and slow rates of water uptake and (3) wrinkled -coated pigmented cultivars which showed intermediate germination and high rates of water uptake.
37
Zou, Tao. "Non-Destructive Bridge Deck Condition Assessment with a Probability-Based Deterioration Threshold." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49384.
Full textAbstract:
Deterioration of bridge decks is an ongoing problem faced by transportation agencies across the country. In past decades, Non-Destructive Evaluation (NDE) techniques, capable of detecting various deteriorations types, e.g., cracking, delamination and reinforcing steel corrosion, have emerged. These techniques generate large amounts of data representing different underlying physics, (decibels for ground penetrating radar and volts for half-cell potential), making data interpretation and comparison difficult for bridge owners and practitioners. The deterioration threshold, or the transition between healthy and deteriorated areas, is essential in understanding NDE data. However, this threshold is determined empirically in former research and engineering practice. In the present research, a probability-based method is proposed to identify deterioration thresholds for specified confidence levels. NDE data measuring different underlying physics are transformed into a binary format by threshold values to compare and combine multiple NDE techniques for bridge deck assessment. The finite element method is also implemented to correlate bridge deck surface stresses with deteriorations measured by NDE techniques, and to study the causes on concrete bridge deck degradation. The general methodology developed in this study will be demonstrated on three bridges, i.e., Virginia, New Jersey and New York Pilot Bridges, which were studied under Federal Highway Administration (FHWA)'s Long-Term Bridge Performance (LTBP) Program.Ph. D.
38
Syverud, Elisabet. "Axial Compressor Performance Deterioration and Recovery through Online Washing." Doctoral thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2080.
Full textAbstract:
Gas turbine performance deterioration can negatively affect overall production capacity of power plants and cause major economic losses. Gas turbines deteriorate from fouling in the compressor section, and online washing is often applied to recover their performance. The success of online washing depends on site-specific issues, and current systems are inconsistent in use and their effectiveness is difficult to test. The objective of this work is to determine the fundamental mechanisms of axial compressor performance deterioration and recovery through online washing.
Empirical data from online washing of RB211-24G at an offshore site were analyzed in the initial phase of research. Empirical data from accelerated salt deterioration and online water washing of a GE J85-13 jet engine were unique to this project. First overall compressor deterioration and single stage performance deterioration were measured using inter-stage gas path instrumentation. Secondly, salt deposits were analyzed to characterize the stage surface roughness and fouling distribution. Finally, recovery through online washing was evaluated. Quasi-one-dimensional models were developed for the GE J85-13 to aid in the test data analysis and to verify the applicability of deterioration loss models to fouled compressors.
The study shows that detection of compressor deterioration can be hampered by nonlinear sensitivities to fouling. Engine control modes must be accounted for to avoid misreading the deterioration rate and production capacity. Flow rate was found as the most sensitive deterioration parameter in the GE J85-13. Fouling affected all parts of the stage characteristics reducing flow, pressure and head. The models successfully reflected the deterioration mechanisms although the effects of deterioration were under-predicted. This study shows the importance of applying Reynolds corrections to deteriorated compressors.
Online washing efficiency is predominantly affected by the water flow rate. Small droplets and low flow rates increase the fouling in the aft stages, and increased injection time cannot compensate for low flow rates. For effective water washing of the entire compressor section the recommended water-to-air ratio is between 0.8 to 2%.
The major contributions of this work are presented in four papers contained in the Appendices.
39
Welte, Thomas. "Deterioration and Maintenance Models for Components in Hydropower Plants." Doctoral thesis, Norwegian University of Science and Technology, Department of Productions and Quality Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2205.
Full text
40
Akoglu, Alp Osman. "Archaeometric Investigations Of Stone Deterioration In Kalecik (ankara) Castle." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614224/index.pdf.
Full textAbstract:
Kalecik Castle is an important historical building. However, dacitic building stone sed is deteriorating mainly because of atmospheric conditions. The purpose of this tudy is to understand the deterioration mechanisms affecting the dacitic stones used n the castle&rsquos walls. To achieve this purpose various arhaeometrical methods such as etrography, X-ray diffraction analyses, analyses for determining physical poperties density, porosity, and water absorption capacities), ultrasonic velocity easurements and some mechanical tests are used. The results of this study show that the deterioration of Kalecik Castle results mostly rom physical factors such as frost action, wetting and drying and thermal shock. According to the study, chemical and biological factors that may also be an mportant cause of deterioration are negligible in Kalecik Castle&rsquo
s building stones.
41
McCormack, Katrina. "The deterioration of concrete by heterothrophic bacteria and fungi." Thesis, University of Central Lancashire, 2001. http://clok.uclan.ac.uk/20212/.
Full textAbstract:
The aim of this investigation was to design and develop a novel decontamination process for concrete, which could harness the deteriorative effect of various microorganisms found within the natural environment by a process known as biodecontamination. Whilst the majority of existing research into concrete deterioration has focused on the effect of sulphur or nitrogen bacteria, this study has investigated the effect of the lesser documented heterotrophic bacteria and fungi on concrete deterioration, and their possible use within a biodecontamination system. A number of heterotrophic bacteria and fungi were isolated and characterised from samples of deteriorating concrete removed from four similar cellars. The deteriorative ability of ten of these bacterial and fungal isolates was established using weight loss analysis. A further evaluation of the deteriorative activity of two of the heterotrophic bacterial and fungal isolates, was investigated by means of Dionex ion exchange chromatography and atomic absorption spectrophotometry, which traced the liberation of key cations as indicators of the deterioration of the calcite binary material which cemented the concrete particulate material together. The results obtained from this study indicated that the calcite binary material was deteriorated after a short period of time as a consequence of ion exchange reactions at the surface of the material between magnesium and calcium cations. Environmental scanning electron microscopy was used to visualise microorganisms at the concrete surface. This technique provided evidence of deterioration, as indicated by the expansion of pores at the material surface. The microorganisms isolated were used to develop two mixed consortia (consortium 1 and consortium 2) in different media. The deteriorative activity of these organisms was compared with an axenic culture of Aspergillus carbonarius, since this fungus produces citric acid, a known deteriorative agent of concrete. Following the selection of these microorganisms, various conditions within the liquid culture medium were altered in an attempt to enhance the levels of deterioration obtained. As a consequence of results obtained from these investigations, it was recommended that the growth medium was supplemented with 5% (w/v) glucose or sucrose and adjusted to pH 6.5 prior to inoculation. It was found that the levels of weight loss, were not enhanced by the addition of sodium chloride or magnesium sulphate salts to the medium. Whilst inoculum level was found to have had an initial effect on the rate at which deterioration occurred, this effect was felt less after a period of twelve weeks. Results obtained from a continuous culture study of consortium 1 and A.carbonarius indicated that biofllms consisting of these microorganisms could be grown on concrete under conditions of minimal surveillance and maintenance. As part of this study, it was decided to develop a gel-based delivery system which consisted of the paint thickener, hydroxyethylcellulose. A gel system was found to confer the advantages of an 'artificial' biofllm environment, and improve the chances of colonisation by increasing the residence time of the microorganisms at the surface. The results obtained indicated that the gel did not inhibit the growth or deteriorative activity of the microorganisms even if the gel was dehydrated.
42
Shetty, Navilkumar. "System reliability of fixed offshore structures under fatigue deterioration." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/7581.
Full text
43
Itoh, Yoshito, Haosheng Gu, Kazuya Satoh, and Yoshihisa Yamamoto. "Long-term Deterioration of High Damping Rubber Bridge Bearing." 土木学会, 2006. http://hdl.handle.net/2237/7459.
Full text
44
Mubaraki, Muhammad. "Predicting deterioration for the Saudi Arabia Urban Road Network." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11171/.
Full textAbstract:
Pavements represent an important infrastructure to all countries. In Saudi Arabia, huge investments have been made in constructing a large network. This network requires great care through conducting periodic evaluation and timely maintenance to keep the network operating under acceptable level of service. Pavement distress prediction and pavement condition prediction models can greatly enhance the capabilities of a pavement management system. These models allow pavement authorities to predict the deterioration of the pavements and consequently determine the maintenance needs and activities, predicting the timing of maintenance or rehabilitation, and estimating the long range funding requirements for preserving the performance of the network. In this study, historical data of pavement distress and pavement condition on the main and secondary road network of Riyadh, Saudi Arabia were collected. These data were categorized, processed, and analyzed. These data have been employed to generate prediction of pavement distress and condition models for the Saudi Arabia Urban Road Network (SAURN). Throughout the study, the most common types of pavement distress on SAURN have been identified. The behavior of these distress types has been investigated. A sigmoid function was found to be an excellent representation of the data. Seven for urban main pavement distress models (UMPDM) have been developed. In addition, six urban secondary pavement distress models (USPDM) have been developed. Moreover, two pavement condition models have also been developed, one for urban main pavement condition (UMPCM), and the other for urban secondary pavement condition (USPCM). The developed models provide a reasonable prediction of pavement condition. The models were assessed by standard error and residual analysis. A suitable procedure for the implementation of the models has also been proposed.
45
Louvros, Dimitrios. "Investigation of the reliability deterioration of ageing marine structures." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8470.
Full textAbstract:
In the present work, an investigation of the fatigue life benefits emerging from
fillet weld geometries optimization has been carried out.
At first, an introduction to ageing mechanisms, corrosion and especially fatigue,
acting on operating marine structures has been made. Residual stresses at
weld toes, stress modes, and types, geometrical factors (weld angle, toe radius,
leg length), welding techniques selected, post-welding treatment and plate‟s
material are some of the principal factors affecting the fatigue life of a fillet weld
joint.
Especially, the accuracy of various approaches in fatigue life estimation of
specific geometries under pre-set types and levels of stress is studied. It is
evident so far that even the notch stress concept is the most accurate method
based on S-N curves, the Fracture Mechanics approach can offer more
accurate solutions of a crack development through the material. Towards this, a
literature review on crack evolution aspects in welded and non-welded plates
under bending and tension was performed; substantial parameters were
determined and finally implemented in the LEFM model which was used for the
simulation purposes of Chapter 6.
As far as the crack aspect ratio evolution is concerned, an extensive reference
is available in literature since many researchers have investigated its
contribution to the determination of geometrical paths, commonly known as
“Preferred Propagation Paths”. Their significance is related with our ability to
determine accurate SIF solutions leading to precise fatigue life estimations.
A typical fillet weld joint 2-D model has been developed in CAE Abaqus
software and a Finite Element Analysis of subject T-profile has been carried out.
Through this analysis, the fillet weld angle, the weld leg length, the weld toe
curvature radio ρ and the carrying load plate thickness are examined for their
impacts on the maximum surface stress. Finally, a number of stress mitigating
measures are proposed and their effects are analyzed.
Undoubtedly, the notch stress concept today is gradually gaining more and
more acceptance among other fatigue analysis practices, hence the need for an
estimation of the actual surface stresses along fillet weld toes, has become
imperative. Towards this, different 2-D geometries are tested against stress
concentration factors developed at weld toes, which are calculated on the basis
of maximum in-plane principal stresses over nominal stresses in mode I pure
bending and pure tension respectively. Moreover, validation with corresponding
results from literature is provided. Finally, three different concepts for reducing
the maximum surface stresses are presented. The first one proposes grinding
of the weld toe area and formulation of an artificial U-notch or a part- circular
profile. The second one applies to non-penetrating welds and assumes the
existence of a root gap of a specific geometry which is related to the fatigue life
and stress concentration factor of the fillet weld joint. Last but not least, the
relatively recent concept of the variable radius notch is discussed, even though
it is applicable mostly to notched bodies, not weld joints.
Afterwards, a Linear Elastic Fracture Mechanics analysis of reference 2D fillet
weld model is demonstrated. A number of geometrical parameters considered
at previous stage for their impact on surface Stress Concentration levels at the
weld toe region, have been correlated to fatigue life benefits in terms of
increased number of stress cycles till failure.
An extensive analysis of 9 different T-butt weld joint geometries has been
provided in order to investigate how positively a possible SCF reduction can
affect the fatigue life of a weld joint. Essential geometric variations (weld angle,
length, toe radius, root slot) were considered in the 2D model. All calculated
benefits both in pure bending and pure tension cases have been reported
accordingly.
Based on a linear interpolation of the points scatter (SCF, N-cycles) both in
banding and tension, it was observed that a surface stress mitigation of 1%
could lead to 1,33 up to 2,5% fatigue life benefit in the range of SCF=2 – 2,5. It
is evident so far that the geometrical optimization of a weld joint in respect of
notch stress mitigation can be a powerful tool both in shipbuilding and
maintenance practice in the future. However, technically wise their application
may incur high initial costs of improved tools of welding and post welding
treatment and robots even though it would consist a cost effective solution in a
medium/long term basis.
Finally, the above process is followed by a reliability analysis of the most critical
geometrical parameters affecting the fatigue life of a fillet weld joint. Reliability
assessment results concerning medium, high and low cycle fatigue are provided
and a comparative analysis of each factor‟s impact on fatigue life has been
carried out.
46
Isiklar, Ali Gungor. "An analysis of Turkish-American relations improvement or deterioration." Thesis, Monterey, California. Naval Postgraduate School, 2008. http://hdl.handle.net/10945/3835.
Full textAbstract:
Turkish-American relations date back to the 1800s; however, they were far from well developed and did not solidify until the end of World War II. After an alliance of fifty years, the Second Iraq War indicated doomsday scenarios in terms of U.S.-Turkish relations in the minds of many scholars. The Turkish Parliament's rejection of the proposal of a second Turkish front for American troops in Northern Iraq, as well as, the July 4 incident in Sulaymaniyah in 2003, froze the dynamics of the relations. Yet, when the history of the relations from the end of World War II until 2003 is examined carefully, it should be clear that every time there was a deterioration of the mutual relations, they were replaced by a period of improvement, as the common interests of both countries outweigh the differences. This thesis aims to show that regardless of the level of deterioration, in terms of mutual relations, Turkish-American relations are inclined to improve. For this reason, it can be assumed that the deteriorated relations of the Second Iraq War will follow the trend toward improvement in the future.
47
Bull, Simon. "Study of post-harvest physiological deterioration in transgenic Cassava." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544507.
Full text
48
Ciccarelli, Gregory Alan. "Early warning of patient deterioration in the inpatient setting." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/100870.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 161-166).
Early signs of patient deterioration have been documented in the medical literature. Recognition of such signs offers the possibility of treatment with sufficient lead time to prevent irreversible organ damage and death. Pediatric hospitals currently utilize simple, human evaluated rubrics called early warning scores to detect early signs of patient deterioration. These scores comprise subjective (patient behavior, clinician's impression) and objective (vital signs) components to assess patient health and are computed intermittently by the nursing staff. At Boston Children's Hospital (BCH), early warning scores are evaluated at least every four hours for each patient. Many hospitals monitor inpatients continuously to alert caregivers to changes in physiological status. At BCH, each hospital bed is equipped with a bedside monitor that continuously collects and archives vital sign data, such as heart rate, respiration rate, and arterial oxygen saturation. Continuous access to these physiological variables allows for the definition of a continuously evaluated early warning score on a reduced rubric. This thesis quantitatively assesses the performance of BCH's current Children's Hospital Early Warning Score (CHEWS). We also apply several standard machine learning approaches to investigate the utility of automatically collected bedside monitoring trend data for prediction of patient deterioration. Our results suggest that CHEWS offers at least a 6-hour warning with sensitivity 0.78 and specificity 0.90 but only with a prohibitively large uncertainty (48 hours) surrounding the time of transfer. Performance using only standard bedside trend data is no better than chance; improvement may require exploiting additional intra-beat features of monitored waveforms. The full CHEWS appears to capture significant clinical features that are not present in the monitoring data used in this study.
by Gregory Alan Ciccarelli.
S.M.
49
Hann, Alistair. "Multi-parameter monitoring for early warning of patient deterioration." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670068.
Full text
50
Isiklar, Ali Grungor. "An analysis of Turkish-American relations improvement or deterioration /." Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Dec/08Dec%5FIsiklar.pdf.
Full textAbstract:
Thesis (M.A. in Security Studies (Europe and Eurasia))--Naval Postgraduate School, December 2008.Thesis Advisor(s): Abenheim, Donald. "December 2008." Description based on title screen as viewed on January 29, 2009. Includes bibliographical references (p. 115-116). Also available in print.