Dissertations / Theses: 'IN 718'

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Chen, Qiguang. "Fatigue and fracture in Inconel 718-copper-Inconel 718 explosion-bonded composites." Thesis, Massachusetts Institute of Technology, 1990. https://hdl.handle.net/1721.1/128798.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990.
Title as it appears in the M.I.T. Graduate List, Feb. 1990: Fatigue and fracture in explosion-bonded Inconel 718-copper-Inconel 718 composites.
Includes bibliographical references.
by Chikuang Chen.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990.

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Zhao, Mengxiong. "Ultrasonic fatigue study of Inconel 718." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100063/document.

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L’Inconel 718 est utilisé dans les disques de turbine des moteurs d’avion, de par sa haute résistance à la corrosion, à l’oxydation, au fluage et sa haute résistance mécanique à très haute température. Le nombre total de cycles de ces composants mécaniques s’élève à 109~1010 durant sa vie. Ils subissent des chargements de grande amplitude à faible fréquence, comme les forces centrifuges ou les contraintes thermiques mais aussi des chargements de faibles amplitudes à très haute fréquence, du aux vibrations des pales. Dans ce travail, on se propose d’étudier la fatigue à très grand nombre de cycles (VHCF) de l’Inconel 718 en utilisant des machines de fatigue ultrasonique, fonctionnant à 20KHz. Le système d’acquisition utilise des cartes NI et le logiciel LabView pour superviser la fréquence, la température, les déplacements durant toute la durée des tests. Des capteurs laser Keyence utilisant deux sondes pour les faces supérieure et inférieure de l’éprouvette permettent de capturer la fréquence et les modes de vibration. La différence entre les valeurs moyennes mesurées permet d’accéder à l’allongement de l’éprouvette, dû à l’auto-échauffement.3 types de matériaux avec différents traitements thermiques, AR, DA et DAHQ de l’ONERA et SAFRAN sont comparés. La différence au niveau de la taille de grain, de la phase, des précipités, … est analysée par micrographie métallographique en utilisant un microscope optique (MO) et un microscope électronique à balayage (MEB). Le comportement en traction quasi-statique et sous chargement cyclique contrainte-déformation est aussi proposé. La transition entre durcissement et adoucissement cyclique apparait à l’issue du traitement thermique. Finalement, les surfaces de ruptures sont observées en utilisant des caméras optiques et un MEB afin d’identifier les mécanismes de ruptures de l’Inconel 718 dans le domaine de la fatigue à très grand nombre de cycles
Inconel 718 is widely used in turbine disk of aeronautic engines, due to its high resistance to corrosion, oxidation, thermal creep deformation and high mechanical strength at elevated temperature. The total cycle of these mechanical components is up to 109~1010 during its whole lifetime. It endures high-amplitude low-frequency loading including centrifugal force or thermal stress, and also low-amplitude high-frequency loading came from vibration of blade.In this work, the very high cycle fatigue (VHCF) behaviour of Inconel 718 with self-heating phenomenon without any cooling is studied using ultrasonic fatigue system at 20KHz. Acquisition system is improved using NI capture card with LabView for monitoring the frequency, temperature, displacement and so on during all the tests. Keyence laser sensor with two probes at the top and bottom surfaces of the specimens is used to reveal the frequency and vibration mode. The difference of mean values between these two probes is the elongation of the specimen caused by self-heating phenomenon.Three sets of materials with different heat treatment, As-Received (AR), Directly Aged (DA) and Directly Aged High Quality (DAHQ) from ONERA and SAFRAN are compared. The difference of grain size, phase, precipitate particle, etc. is investigated by metallographic micrograph using optical microscope (OM) and scanning electron microscope (SEM). Quasi-static uniaxial tensile property and cyclic stress-strain response is also proposed. The transition from cyclic hardening to cyclic softening appears after aged heat treatment. Finally, fracture surfaces are observed using optical camera and scanning electron microscope in order to identify the mechanism of fracture of Inconel 718 in the VHCF domain

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Cao, Pengcheng. "Characterization of Laser Deposited Alloy 718." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-182603.

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Additive Manufacturing (AM) is a method of producing three-dimensional objects using additive processes. It allows great flexibility in the processes and reduces the design-to-production time. Laser Metal Deposition (LMD) is one of AM methods under development and is based on the deposition technology. LMD has advantages in grain growth control, material functional grading, lower material storage requirement and more spatial freedom. Considering the outstanding features, it is important to study the characteristics of LMD products, which in this study is Alloy 718 for aerospace applications. Single-wall Laser LMD samples are built with varied process parameters using gas-atomized Alloy 718 powders. Two experiments were carried out with focuses on 1) evaluations and comparisons of the microstructural characteristics, porosity and hardness of the samples are performed; 2) The effect of heat treatments including solution treatment and aging on the microstructure as well as the hardness. The results of the experiments revealed directional solidification features and typical phases such as γ matrix, Laves phase and carbide. 0.06% average porosity and a majority of < 20 µm size are measured from the LMD samples. Only spherical gaseous pores are found while no lack-of-fusion pore is found. A hardness Vickers of 246 in average hardness is measured from the LMD samples. In the heat treated samples, δ phases were found; By direct-aging at 750 ℃ for 10 to 15 hours, the samples reach a maximum hardness of around 382 HV. The same hardness was reached by 1 hour of solution treatment at 950 ℃ followed by 5 hours aging at 750 ℃. The effects of processing parameters on the characteristics of LMD processed Alloy 718 are compared and discussed. A 2-dimentional map of porosity distribution along the length of the sample is made and the patterns are investigated along both the length and the height of the sample. It is found in the sample that the starting part of the deposit is higher in number of pores while the finishing part is larger in pore size. It is also found that the top layer of the deposit has the highest porosity level, pore number and pore size. Moreover, the hardness gradient along the build-up direction is evaluated and discussed. No significant hardness gradient was found. The precipitation hardening effect of LMD process and possible improvements are also discussed.

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Knock, Nathaniel Oscar. "CHARACTERIZATION OF INCONEL 718: USING THE GLEEBLE AND VARESTRAINT TESTING METHODS TO DETERMINE THE WELDABILITY OF INCONEL 718." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/396.

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Nickel based superalloys were developed to withstand the severe thermal and mechanical environment associated with rocket propulsion systems and jet engines. In many alloy systems the strength of a component rapidly deteriorates as the operating temperature increases. Nickel based superalloys, however, retain strength over a range of temperatures which includes the operating range for many propulsion systems. This improved performance is accomplished by a combination of solid-solution strengthening, precipitation strengthening and grain-boundary strengthening. Furthermore, super-alloy systems are designed for ease of fabrication, to include machining, welding and heat treating. Inconel 718 was developed to overcome problems with post-weld cracking that were common in precipitation hardened nickel based superalloys strengthened by γ’. Inconel 718 is strengthened by γ’’ and is less sensitive to cracking during post-weld thermal treatment. However, in some cases, compositional changes which improved the behavior of these alloys during stress relief actually led to greater difficulty during the joining process. Many approaches have been used to determine the hot-cracking sensitivity of Inconel 718. Historically, two approaches have been particularly valuable because of their repeatability, their ability to compare different alloy systems and their verisimilitude to actual fabrication. These are the Gleeble hot-ductility test and the Variable-Restraint (Varestraint) weld test. Varestraint samples were prepared as per standard preparation techniques and tested longitudinally with a GTAW. At a predetermined location a strain was applied perpendicular to weld direction. The applied strain varied from 0.25%, 0.5%, 1.0%, 2.0%, and 4.0%. The Inconel 718 yielded a maximum crack length of 0.6 mm with a saturation strain of 2.0%. Both the total crack length and the number of cracks did not have a saturation strain. Gleeble samples were prepared from rod stock and tested with standard methodology to determine the characteristic temperatures: nil ductility, nil strength, and ductility recovery temperature of Inconel 718. The samples were tested at various pull temperatures on-heating until the nil strength temperature then tested on-cooling with the nil strength temperature acting as the peak temperature. The nil strength temperature was 2273°F, nil ductility temperature was 2182°F, and the ductility recovery temperature was 1925°F. Both the Varestraint and Gleeble results were compared with relevant literature to determine the weldability of the Inconel 718. Four criteria were used to determine the weldability of Inconel 718 and in three of the four tests; the Inconel 718 had equal to or greater weldability than the compared materials. In the fourth test, the Inconel 718 demonstrated lower weldability than the compared alloy systems, however, Inconel 718 operates in different conditions specifically, the high temperature and pressure conditions mentioned above.

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Tavakoli, Manshadi Salar. "Laser assisted machining of Inconel 718 superalloy." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40803.

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This research work assesses the effect of Laser Assisted Machining (LAM) on the machinability of Inconel 718 using a triple layer coated carbide and a sialon ceramic tool. This study was motivated by issues related to poor machinability of IN718 under conventional machining operations. In this work a focused Nd:YAG laser beam was used as a localized heat source to thermally soften the workpiece prior to material removal. Finishing operations were assumed throughout the experiments. Optimization screening tests were performed over a wide range of cutting speeds (ranging from 100 to 500 m/min) and feeds (ranging from 0.125 to 0.5 mm/rev). Results showed a significant drop in all three components of cutting force when thermal softening caused by the laser power was in effect. These tests yielded the optimum cutting speed and feed to be 200 m/min and 0.25 mm/rev for the coated carbide and 300 m/min and 0.4 mm/rev for the ceramic tool. Under these optimum conditions tool life tests were carried out. Drastic increase in terms of the material removal rate (MRR) was demonstrated under LAM conditions as compared to conventional machining. A nearly %300 increase in MRR was established for the coated carbide tool while slightly reducing tool life, mainly because the coatings offering thermal and wear protection could not withstand the high temperatures associated with LAM. Nearly %800 increase in MRR for the ceramic tool was achieved while improving tool life (about %50). In all cases, improvements in surface finish and surface integrity were observed. The dominant mode of tool failure was observed to be average flank wear for all tools tested. However, the coated carbide tool exhibited signs of chipping and flaking in the coatings. The morphology of the chips produced was analyzed and it was shown that temperature and increased chip thickness were the main causes of transition from steady state to shear localized chip structure. Shear localized or sawtooth chips tended to
Cette recherche évalue l'effet de l’usinage assisté par Laser (UAL) sur l’usinabilité d'Inconel 718 en utilisant deux outils : Le premier est enrobé d’une triple couche de carbure et le second est en céramique sialon. Cette étude a été motivée par la difficulté d’usiner IN718 conventionnellement. Dans ce travail, un rayon laser Nd:YAG a été utilisé comme une source de chaleur localisée pour adoucir thermiquement la pièce avant l'usinage. Les expériences représentaient les opérations de finitions. Une optimisation a été exécutée à travers une sélection unitaire pour une large gamme de vitesses de coupes (aux limites de 100 à 500 m/min) et de vitesses d’avance (aux limites de 0.125 à 0.5 mm/rév). Les résultats ont manifesté une réduction significative dans toutes les trois composantes de la force de coupe quand l'adoucissement thermique provoqué par le laser était mis en effet. D’après les tests, les valeurs optimales de vitesse de coupe et d’avance sont 200 m/min et 0.25 mm/rév pour l’outil avec la couche de carbure et 300 m/min et 0.4 mm/rév pour l’outil en céramique. Dans ces conditions optimales, des épreuves de tenue d’outils ont été réalisées. Une augmentation du taux d’enlèvement de matière a été démontrée lors de l’application de l’UAL en comparaison à l’usinage conventionnel. Une augmentation dans le taux d’enlèvement de matière de 300% a été établie pour l’outil enrobé de carbure avec une légère réduction en tenue d’outil. La raison de cette réduction est le fait que ces couches qui offrent une protection thermique et une résistance d’usure ne pouvaient pas résister aux températures élevées associées à l’UAL. Une augmentation de 800% dans le taux d’enlèvement de matière a été accomplie pour l’outil en céramique avec une amélioration de tenue d’outils d’environ 50%. Dans tous les cas, une amélioration de l’intégrité de la surface à ét

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Balachandramurthi, Arun Ramanathan. "Fatigue Properties of Additively Manufactured Alloy 718." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13186.

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Additive Manufacturing (AM), commonly known as 3D Printing, is a disruptive modern manufacturing process, in which parts are manufactured in a layer-wise fashion. Among the metal AM processes, Powder Bed Fusion (PBF) technology has opened up a design space that was not formerly accessible with conventional manufacturing processes. It is, now, possible to manufacture complex geometries, such as topology-optimized structures, lattice structures and intricate internal channels, with relative ease. PBF is comprised of Electron Beam Melting (EBM) and Selective Laser Melting (SLM) processes. Though AM processes offer several advantages, the suitability of these processes to replace conventional manufacturing processes must be studied in detail; for instance, the capability to produce components of consistent quality. Therefore, understanding the relationship between the AM process together with the post treatment used and the resulting microstructure and its influence on the mechanical properties is crucial, to enable manufacturing of high-performance components. In this regard, for AM built Alloy 718, only a limited amount of work has been performed compared to conventional processes such as casting and forging. The aim of this work, therefore, is to understand how the fatigue properties of EBM and SLM built Alloy 718, subjected to different thermal post-treatments, is affected by the microstructure. In addition, the effect of as-built surface roughness is also studied. Defects can have a detrimental effect on fatigue life. Numerous factors such as the defect type, size, shape, location, distribution and nature determine the effect of defects on properties. Hot Isostatic Pressing (HIP) improves fatigue life as it leads to closure of most defects. Presence of oxides in the defects, however, hinders complete closure by HIP. Machining the as-built surface improves fatiguelife; however, for EBM manufactured material, the extent of improvement is dependent on the amount of material removed. The as-built surface roughness, which has numerous crack initiation sites, leads to lower scatter in fatigue life. In both SLM and EBM manufactured material, fatigue crack propagation is transgranular. Crack propagation is affected by grain size and texture of the material.

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Banazis, Michael. "Development of tools for surveillance of Coxiella burnetii in domestic ruminants and Australian marsupials and their waste." Banazis, Michael (2009) Development of tools for surveillance of Coxiella burnetii in domestic ruminants and Australian marsupials and their waste. PhD thesis, Murdoch University, 2009. http://researchrepository.murdoch.edu.au/718/.

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The aim of this study was to develop improved methods to detect viable Coxiella burnetii in wastes from livestock production. The impetus for this work arose because there is a significant risk of infection for humans attributed to contact with waste products from the livestock production industry. This situation is further compounded by the lack of suitable tools to detect viable C. burnetii in these wastes. In addition, effective disinfection strategies for livestock wastes are also required to reduce the risk of infection with C. burnetii for individuals that come into contact with these waste products. A quantitative real-time PCR system (qPCR) with high sensitivity and specificity was developed to detect the C. burnetii in environmental samples associated with domestic ruminants and native Australian marsupials. Different detection chemistries and procedures were evaluated based on their sensitivity, specificity and reproducibility. Overall it was found that the TaqMan PCR targeting the IS1111a locus provided the most sensitive and reproducible test. The Geneworks PowerSoil(tm) DNA isolation kit provided the best compromise between reproducibility and recovery of DNA from livestock wastes. When combined, the IS1111a TaqMan qPCR and Geneworks PowerSoil DNA Extraction Kit provided a test which was capable of detecting as few as two C. burnetii genome equivalents in 0.2g of soil or faeces. Coxiella burnetii has been shown to display extreme resistance to environmental exposure. Therefore, assessment of the viability of the organism in environmental matrices is more useful for risk assessment programs than detection of DNA alone. A quantitative reverse transcriptase PCR was developed that was able to detect viable C. burnetii cells in soil. The sensitivity of the assay was enhanced by heat-treating the soil samples prior to extraction of RNA. The factor most often associated with transfer of C. burnetii to humans is exposure to livestock or their waste. Therefore, decontamination of waste from livestock production industries is a key factor in preventing outbreaks of Q fever. A system was developed to determine the efficacy of various disinfectant treatments against the environmental pathogen C. burnetii. Treatments evaluated included sodium hypochlorite, ozone, ultraviolet light, peracetic acid (PAA), and Virkon S®. Sodium hypochlorite at a concentration of 0.1 mM reduced the infectivity of C. burnetii by over 92% while treatment with the same sodium hypochlorite concentration in wastewater showed significantly reduced efficacy. Despite this reduced potency, sodium hypochlorite is still useful for control of C. burnetii in the liquid waste of animal production. Commercially available ELISA and CFT assays exist for ruminants but there are no immunological tests available for detecting C. burnetii in marsupials even though Australian marsupials are known to be susceptible to C. burnetii. An indirect ELISA for detecting anti-Coxiella antibodies in kangaroos was developed. Paired serum and faecal samples were taken from 379 ruminants from Western Australia and the serum was tested with a commercially available ELISA and the complement fixation test while the faeces was tested using the qPCR developed during this study. Paired serum and faecal samples were taken from 343 kangaroos from WA and were tested with the antibody-ELISA developed during this study and by qPCR. A very low prevalence of anti-Coxiella antibodies was observed in the ruminants sampled and results from immunological tests correlated poorly with qPCR data. The development of an ELISA for use with kangaroo serum was problematic because of the lack of reference sera from animals known to be infected with C. burnetii. Despite this results from the ELISA developed suggested that the apparent seroprevalence in the WA animals surveyed was approximately 34%. Results from testing kangaroo faeces with the qPCR correlated poorly with the results from the antibody-ELISA. These data suggest that kangaroos may be a significant reservoir of C. burnetii in Western Australia and due to cohabitation of kangaroos and domestic ruminants, may provide a link between the wildlife and domestic cycles of C. burnetii.

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Dussauge, Laguna Mauricio Ivan. "Cross-national policy learning and administrative reforms : the making of 'management for results' policies in Chile and Mexico (1990-2010)." Thesis, London School of Economics and Political Science (University of London), 2013. http://etheses.lse.ac.uk/718/.

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The study of whether and how learning from abroad matters for policy changes is a fundamental but hugely contested subject at the heart of contemporary policy transfer, policy diffusion, and cognate literatures. Cross-national learning is said to be one of the key mechanisms by which ideas, policies, and administrative reforms travel across jurisdictions. However, it is also said to be fraught with several difficulties, and thus to hardly exert any significant influence on policymaking. This thesis addresses this puzzle through various means. It asks a set of research questions and proposes an analytical framework to explore the relationship between cross-national learning and policy change. It then traces the making of Management for Results policies in Chile and Mexico, comparing policy developments in both countries across two decades (1990-2010). The thesis challenges conventional scholarly accounts on this subject. It shows that cross-national learning might bring about significant policy changes. However, this does not necessarily occur through the transfer or diffusion of policies or models intact. It happens through policymakers’ use of knowledge from policies abroad in many ways and at various stages of the policymaking process. Moreover, policy changes are neither secured once policy elements are adopted, nor are they completed once their process of adaptation to a receiving environment has started. In fact, policymakers need to devise strategies to ensure the new policies are effective, legitimate, and durable. Full policy convergence does not necessarily happen, but neither does absolute divergence. Across time, through sequences of learning and change, policymakers learn how to overcome cognitive biases and national barriers; how to combine experiential learning and knowledge from policies abroad; and how to better fit policies to their national conditions, while also keeping them in tune with international policy developments.

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Oleksik, Gerard. "Music in the age of the Internet : an investigation into the relationship between music, music use and technology." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/718/.

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Landa, Tucto Apolos Baltazar. "Health and healing in mission work at the start of the twenty-first century a biblical, historical and contemporary study /." Thesis, Thesis restricted. Connect to e-thesis record to view abstract. Move to record for print version, 2008. http://theses.gla.ac.uk/718/.

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Thesis (MTh.(R)) - University of Glasgow, 2008.
MTh.(R) thesis submitted to the Department of Theology and Religious Studies, Faculty of Arts, University of Glasgow, 2008. Includes bibliographical references. Print version also available.

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Stapley, Torstein. "A grounded theory study on the development of a professional identity in trainee counselling psychologists." Thesis, London Metropolitan University, 2014. http://repository.londonmet.ac.uk/718/.

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This study set out to explore the development of a professional identity in trainee Counselling Psychologists in the United Kingdom. Professional identity development involves the acquisition of attitudes, values, knowledge and skills pertaining to the profession (Page, 2005), as well as the acquirement of new role behaviours and new views of the self (McElhinney, 2008). Bucher and Stelling (1977) argued that the basic foundation of a professional identity is constructed during the professional training period when the individual undergoes an initial socialisation to the profession. Yet, research exploring professional identity development in trainee Counselling Psychologists in the UK is limited. Adopting a constructivist grounded theory approach (Charmaz, 2006), this research expected to identify and understand which factors aid and inhibit professional identity development in trainee Counselling Psychologists. Semi-structured interviews were used to explore how nine trainee Counselling Psychologists from a selection of universities and training stages experienced the development of their professional identity. Four interconnected concepts were identified as influential in professional identity development: process, competing/selling, character and subjugating. The results indicated that professional identity development involves attaining a sense of authority, competence, responsibility and autonomy in the professional role through engagement with self, others and the wider contexts of the training. Role ambiguity and role conflict were found to impede the trainee’s identification with the professional role. It appears that the process of developing a professional identity includes a willingness to negotiate tensions between the subjective and the objective, engage with a multitude of demands, and that the development of a professional identity occurs throughout the training. The findings were discussed, with particular consideration to how trainee Counselling Psychologists can be facilitated in their development of a professional identity.

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Del, Giovane Cinzia <1979&gt. "Modello multilevel a classi latenti: estensione al modello multidimensionale." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/718/.

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Chang, Min Carleton University Dissertation Engineering Mechanical. "Damage tolerance of Inconel 718 turbine disc material." Ottawa, 1991.

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Yang, Libin. "Modelling of the inertia welding of Inconel 718." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/760/.

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In this study, the inertia welding process was studied by both an FEM model and three analytical models. The thermal analysis shows that there is a steep temperature gradient near the mating surface, which is the cause for the existence of a band of high hydrostatic stress near the weld line. The holding effect of this high static stress is the reason for the presence of the very soft material at the welding interface. The models were used to predict the displacement of the weld line (upset) with a lambda model to describe the constitutive relation of IN718 at high temperature. The results from the different models are in broad agreement. The shear stress induced by friction at the interface is found to enlarge the upset value; its effect must be taken into account if the upset is to be predicted accurately. The extrusion of the burr during the last second of the welding is a direct result of the quick stop of the rotating part due to the balance of the momentum, which is clearly explained by the analytical mechanical model put forward in this work.

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Kumara, Chamara. "Microstructure Modelling of Additive Manufacturing of Alloy 718." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13197.

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In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

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Deng, Dunyong. "Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties." Licentiate thesis, Linköpings universitet, Konstruktionsmaterial, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-144491.

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Additive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome. Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases λ’/λ’’ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships. The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments. For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture. Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is “work-hardened” by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can minimize this difference. Results from this licentiate thesis provide the basis for the further research on the cyclic mechanical properties of EBM and SLM IN718, which would be the focus of following phase of the Ph.D. research.

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Gustafsson, David. "High temperature fatigue crack propagation behaviour of Inconel 718." Doctoral thesis, Linköpings universitet, Hållfasthetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85934.

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The overall objective of this work has been to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. The fatigue crack propagation behaviour under high temperature hold times has been studied. Firstly, the main fatigue crack propagation phenomena have been investigated with the aim of setting up a basis for fatigue crack propagation modelling. Secondly, modelling of the observed behaviour has been performed. Finally, the constitutive behaviour of the material has been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures. This thesis is divided into two parts. The first part describes the general framework, including basic observed fatigue crack propagation behaviour of the material when subjected to hold times at high temperature as well as a background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the seven included papers.

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Gustafsson, David. "Constitutive and fatigue crack propagation behaviour of Inconel 718." Licentiate thesis, Linköpings universitet, Hållfasthetslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72610.

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In this licentiate thesis the work done in the TURBO POWER project Influence of high temperature hold times on the fatigue life of nickel-based superalloys will be presented. The overall objective of this project is to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. Firstly, the constitutive behaviour of the material has been been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures. Secondly, the fatigue crack propagation behaviour under high temperature hold times has been studied. Focus has here been placed on investigating the main fatigue crack propagation phenomena with the aim of setting up a basis for fatigue crack propagation modelling. This thesis is divided into two parts. The first part describes the general framework, including basic constitutive and fatigue crack propagation behaviour as well as a theoretical background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the four included papers.

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Bach, H. T., T. A. Saleh, S. A. Maloy, O. Anderoglu, T. J. Romero, M. A. Connors, C. T. Kelsey, E. R. Olivas, and K. D. John. "Post irradiation evaluation of inconel alloy 718 beam window." Helmholtz-Zentrum Dresden - Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-166275.

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Introduction Annealed Inconel 718 alloy was chosen for the beam window at the Los Alamos Neutron Science Center (LANSCE) Isotope Production Facility (IPF) [1]. The window was replaced after 5 years of operation. Mechanical properties and microstructure changes were measured to assess its expected lifetime. Material and Methods A cutting plan was developed based on the IPF rasterred beam profile (FIG. 1). 3-mm OD samples were cut out from the window and thinned to 0.25-mm thick. Shear punch tests were per-formed at 25 °C on 21 samples to quantify shear yield, ultimate shear stress, and ductility. From 1-mm OD, 0.25-mm thick shear punched out disks, 4 TEM specimens of ~30×10×2 μm were obtained using standard FIB lift-out techniques. TEM was performed on an FEI Tecnai TF30-FEG operating at 300 kV. Results and Conclusions TABLE 1 shows MCNPX tally results of accumulated dpa, He and H content from both protons and neutrons fluences and ANSYS steady-state irradiation temperature for the 3-mm OD samples [2]. These peak values are at the peak density of Typically increases in shear yield and shear maximum stress occur with increasing dose. In this case, highest shear yield and ultimate stress was on the lowest dose samples at the outer edge (FIG. 2). Optical microscopy images of the fracture surfaces on the shear punched out disks show no significant change in the fracture mode or reduction in ductility in the un-irradiated, high and low dose irradiated samples. One un-irradiated and 4 irradiated samples (5, E, 16 and 19) were selected for TEM analysis. Figure 3 shows bright field TEM images of an un-irradiated, high and low dose irradiated samples. Un-irradiated sample shows some dislocations and some large precipitates. The high dose sample #5 (~11 dpa, 122 oC) shows small loops and dislocations (left and center images) and no γ\' or γ\'\' precipitates in SAD from z = [011] (right image). Low dose sample #19 (~0.7 dpa, 40 oC) shows a high density of dislocation loops (left image), high density of H/He bubbles (center image) and presence of γ\'\' precipitates in SAD from z = [011] (right image). Radiation induced-hardening is highest at the low dose region in the outer most edge. The hardening from γ\'\' precipitates is determined to be more pronounced than that from trapped bubbles. The lack of significant hardening in the highest dose region is attributed to a lower dis-location density and no γ” precipitates or bubbles [3]. Identification of H or He bubbles and the higher accumulation of these bubbles in the low dose region (no direct beam hitting) warrant further studies. Despite the evidence of irradiation-induced hardening, this spent beam window appears to retain useful ductility after 5 years in service. At the conclusion of 2013 run cycle, the current in-service beam window had reached the same dpa as of the spent window. We plan to extend the service of the current in-service window until it reaches its intended design threshold limit of ~20 dpa (in the highest dose region). Additional measurements at higher dpa values will enable better decision-making in managing risks of the window failure.

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Tanner, David W. J. "Life assessment of welded INCONEL 718 at high temperature." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10796/.

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The overall aim behind this work was to gain and apply an understanding of the mechanical effects of welding, in order to mitigate distortions that had previously hampered uniaxial testing of tungsten inert gas (TIG) butt-welded, thin-section, nickel-base superalloy INCONEL 718 (IN718). With this aim achieved, better test data could be obtained, leading to more reliable material data for IN718 welds, which can be used for more accurate life assessments for shell structures and components. ABAQUS finite element (FE) simulations of the arc welding process were used to understand the development of welding-induced distortions and reduce their prevalence. An efficient, distortion-mitigating welding procedure, devised using the numerical simulations, was used to manufacture TIG butt-welded specimens that were free of distortion. Uniaxial tensile, creep and high temperature (620°C) fatigue tests were performed on both welded and non-welded IN718 specimens. It was found that IN718 welds are significantly less ductile than the parent material, and although welded IN718 exhibits comparatively little loss of tensile strength, its creep and high temperature fatigue properties are severely compromised. The lower performance of the welded specimens was attributed to the microstructural differences when compared with the non-welded material. The mechanical properties of the IN718 weld material were calculated and verified using FE analyses, based on the test data obtained. A continuum damage mechanics approach was employed for creep modelling and the necessary material constants were determined. A Smith, Watson and Topper (SWT) strain range parameter was proposed for fatigue life assessment, based on validation obtained using the test data. Three-dimensional, quasi-static elastic-plastic and creep FE analyses were used for a life assessment case study of an IN718 generic spoke structure. The effect of including a weld in a critical region was investigated for both constant (creep) and cyclic loading conditions at 620°C.

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Sugahara, Tarcila. "Estudo do comportamento em fluência da superliga Inconel 718." Instituto Tecnológico de Aeronáutica, 2011. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2001.

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Esta proposta de trabalho de mestrado tem como objetivo estudar o comportamento em fluência da superliga Inconel 718. A liga foi submetida a ensaios de fluência na modalidade de carga constante, nas temperaturas de 650, 675 e 700C. A faixa de tensão utilizada foi determinada por ensaio de tração a quente e variou de 625 a 814 MPa. Deve ser ressaltado que estudos completos de ensaio de fluência da superliga Inconel 718 são escassos na literatura. O presente projeto é inovador, permitindo o conhecimento mais detalhado da superliga Inconel 718. Foram obtidos conjuntos de curvas e parâmetros experimentais relativos às regiões primária, secundária e terciária, em função das tensões e temperaturas aplicadas. Foram avaliados a ductilidade, a taxa de fluência estacionária e o tempo de vida. A caracterização microestrutural, com o emprego da técnica de microscopia eletrônica de varredura, foi uma ferramenta valiosa para a compreensão dos mecanismos de fluência. Foram realizados ensaios de tração a quente, a fim de se determinar as propriedades mecânicas da superliga nas temperaturas de ensaio de fluência e ensaios de oxidação, a fim de se analisar a influência da formação de óxidos nos resultados dos ensaios de fluência. As técnicas de caracterização utilizadas nesse trabalho foram: microscopia eletrônica de varredura (MEV), para análise fractográfica e microestrutural; microscopia eletrônica de transmissão (MET), para análise de precipitados; difração de raios X rasante, para análise de formação de óxidos; indentaçãop Vickers. A liga apresenta comportamento típico em fluência com a presença dos três estágios de fluência. O estágio secundário foi predominante durante o ensaio; a taxa mínima de fluência apresentou aumento significativo com o aumento da tensão aplicada. A análise do valor do expoente de tensão (n=36,48527) e da energia de ativação (Qc= 512,97), sugere que o mecanismo de fluência a 650 C é o mecanismo de escalagem de discordâncias. Dependendo da temperatura de trabalho do Inconel 718, podem ocorrer dois tipos de fratura: fratura dúctil a 650 e 700C e fratura do tipo intergranular a 675C.

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Marques, Armando. "Torneamento de Inconel 718 com aplicação de lubrificantes sólidos." Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/14776.

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Fundação de Amparo a Pesquisa do Estado de Minas Gerais
The nickel-based superalloys have a high mechanical strength which remains at elevated temperature, high creep and fatigue resistances and excellent oxidation resistance. This makes these alloys highly recommended for use in high temperature working environments such as mechanical components for the aerospace industry. However, these characteristics are major problems when machining them, as it promotes high heat generation in the flow zone, resulting in the development of high wear rates on the cutting tools. In order to reduce the problems caused by the high temperatures generated, the application of a cutting fluid, when possible, is essential to reduce friction at the chip-tool-workpiece interfaces and lower the temperatures in the cutting zone. Seeking to further increase in the efficiency of cutting fluids during machining of nickel alloys, this work presents a study of the influence of solid lubricants, graphite and molybdenum disulphide (MoS2) mixed to a vegetal based cutting fluid, applied by conventional method (flooding) and minimal quantity of fluid - MQF in turning of Inconel 718 with carbide and ceramic (mixed, whisker and SiAlON) tools. When turning with cemented carbide tools the addition of graphite to the cutting fluid provided the best results, while with ceramic tools MoS2 presented the best performance. The life of the carbide tool had an average increase above 200% in conventional flooding application of cutting fluid when compared to MQF, regardless the addition of solid lubricant. The addition of solid lubricants promoted an increase in the life of whisker and SiAlON tools. The flank wear was dominant for cemented carbide tools and SiAlON ceramics, while for whisker and mixed ceramics the notch wear was predominant. Attrition and diffusion wear mechanism were observed in all evaluated conditions. The addition of solid lubricant to the cutting fluid provided significant improvements in the surface roughness values for most of the evaluated conditions. However, there were no significant changes in the machining forces and cutting temperature. The residual stress was tensile and compression, depending on the fluid application method. Overall, the addition of solid lubricant showed no significant differences.
As superligas à base de níquel apresentam alta resistência mecânica que se mantém em elevadas temperaturas, altas resistência à fluência e à fadiga e excelente resistência a oxidação. Isso torna estas ligas altamente recomendadas para utilização em ambientes que trabalham a altas temperaturas, como por exemplo na fabricação de componentes mecânicos para a indústria aeroespacial. Entretanto, esta característica representa um grande problema quando elas são usinadas, pois promove elevada geração de calor na zona de fluxo, implicando no desenvolvimento de altas taxas de desgaste da ferramenta de corte. A fim de reduzir os problemas causados pelas altas temperaturas geradas, a aplicação de um fluido de corte, quando possível, é essencial, proporcionando redução do atrito na interface cavaco-ferramenta-peça e menores temperaturas na zona de corte. Na busca de aumentar ainda mais a eficiência dos fluidos de corte na complexa usinagem das ligas de níquel, este trabalho apresenta um estudo da influência dos lubrificantes sólidos grafite e bissulfeto de molibdênio (MoS2) misturado a um fluido de corte de base vegetal, aplicados pelo método convencional (jorro) e mínima quantidade de fluído MQF, no torneamento do Inconel 718, com ferramentas de metal duro e cerâmicas (mista, whisker e SiAlON). No torneamento com ferramentas de metal duro a adição de grafite ao fluido de corte proporcionou os melhores resultados, enquanto que no torneamento com ferramentas cerâmicas, foi o MoS2 que apresentou melhor desempenho. A vida da ferramenta de metal duro teve um incremento acima de 200% na usinagem convencional (jorro) quando comparado com a usinagem por MQF, sem considerar a adição do lubrificante sólido. A adição de lubrificantes sólidos promoveu um incremento na vida das ferramentas whisker e SiAlON. O desgaste de flanco foi predominante para as ferramentas de metal duro e cerâmica SiAlON, enquanto que nas cerâmicas whisker e mista o desgaste de entalhe foi predominante. Os mecanismo de desgaste de attrition e difusão foram observados em todas as condições avaliadas. A adição de lubrificante sólido ao fluido de corte proporcionou melhorias significativas nos valores da rugosidade para a maioria das condições avaliadas. No entanto, não se observou mudanças significativas nas forças e temperatura de usinagem. As tensões residuais foram de tração e compressão, dependendo do método de aplicação do fluido. No geral, a adição do lubrificante sólido não apresentou diferenças significativas.
Doutor em Engenharia Mecânica

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Dugauguez, Olivier. "Application of unconventional methods on lnconel 718 MIM components." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD045.

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Le procédé de moulage par injection de poudres métalliques (MIM) permet la réalisation de composants métalliques de formes complexes. Il permet la fabrication de moyenne ou grande série via la combinaison de l’injection thermoplastique avec la métallurgie des poudres. Le procédé MIM est un procédé multi-étape qui commence par l’élaboration d’un feedstock, qui est obtenu par mélange de différents polymères avec une poudre métallique. Il est ensuite injecté à l’intérieur d’un moule afin de lui donner la forme désirée. Afin de pouvoir obtenir une pièce métallique dense, les polymères sont progressivement éliminés soit via l’utilisation d’un solvant, soit par dégradation thermique. La pièce est ensuite densifiée grâce à l’application d’un traitement thermique adapté au matériau. Les travaux de cette thèse ont étés initiés par le projet FUI ProPIM, qui réunit différents partenaires industriels et laboratoires de recherche régionaux autour de la fabrication de pièces en superalliage base nickel chrome. Le procédé conventionnel MIM nécessite des cycles gourmands en temps et en énergie lors des étapes de déliantages et de frittages. Ces travaux présentent la recherche de nouvelles méthodes afin d’accélérer ces étapes tout en conservant les propriétés de base du matériau. La recherche de la maitrise de ces étapes est présentée ainsi que les effets de ces nouvelles méthodes sur les propriétés des composants obtenus. Une alternative à l’utilisation de solvants pour extraire les polymères du feedstock a été récemment mise en avant via l’utilisation de fluides à l’état supercritique. La recherche de compatibilité avec les feedstocks dans le cadre du projet ainsi que l’optimisation des paramètres permettant les meilleures conditions d’extraction sont présentées. Le traitement thermique des poudres métalliques pour obtenir un composant dense nécessite l’utilisation de fours pendant des cycles de plusieurs heures. Deux méthodes de frittage dites « non-conventionnelles » ont étés sélectionnées pour leur capacité à réaliser la densification rapidement. La première est le Field Assisted Hot pressing qui combine l’application de pression à l’utilisation de courant électrique pour réaliser le frittage. La deuxième consiste à appliquer des micro-ondes. L’application des méthodes et l’optimisation des cycles de frittage sont présentées ainsi que les effets sur la microstructure des composants métalliques obtenus, ainsi que sur les performances mécaniques
The metallic powder injection moulding process is used for the elaboration of complex shape metallic components. It is efficient for mass production for medium to large series via the combination of thermoplastic injection with powder metallurgy. The MIM process is a multi-step method starting with the elaboration of a feedstock, obtained by mixing different polymers with a metallic powder. It is injected into a die cavity mould to obtain the deigned shape. In order to obtain a dense metallic component, the polymers are progressively extracted by either solvent or thermal debinding. The densification of the component by applying a thermal treatment adapted to the material. This PhD work was initiated by the project FUI ProPIM gathering different industrials and research laboratories around the elaboration nickel-chrome superalloys components. The conventional MIM process has to be performed with time and energy consuming treatment cycles during debinding and sintering. The goal of this work presents new methods developed to accelerate these treatments while at least keeping the same properties of the material. The research presents the optimization of these methods as well as the effects on the properties of the components. The first is an alternative to the organic solvent debinding used to extract polymers of the MIM feedstock. It is replaced by a fluid in a supercritical state. The study of the compatibility and of the performance of the method on the feedstocks is the main concern. The optimization of the debinding parameters and the effects on the final quality of the product is presented. Then, the sintering and the thermal treatment of the metallic powders needs furnaces with controlled atmospheres for extensive periods of time. Two unconventional sintering methods were selected for their capacity to perform the thermal treatments at a high heating rate. The first method is the Field Assisted Hot pressing which combines the application of a pressure with a high intensity current to rise the temperature. The second is the irradiation of the powder by microwaves. The two methods have to be adjusted to the MIM components. The development of the two methods and the effect on the microstructure and the mechanical performances of the material are investigated

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24

Ressa, Aaron. "Plastic Deformation and Ductile Fracture Behavior of Inconel 718." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449001835.

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Kuo, Min. "Dissimilar friction welding of titanium alloys to alloy 718 /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487846354483177.

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26

Sjöberg, Ted. "Plasticity modelling of nickel based super alloy Alloy 718." Licentiate thesis, Luleå tekniska universitet, Material- och solidmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16884.

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The ever growing demand on reduced fuel consumption in modern aircrafts puts high requirements on manufacturers to reduce weight in all parts of the aircraft. With a total weight of up to one fifth of an aircraft’s total operating weight, ways to decrease the weight of the engine systems are continuously sought. The containment structure that surrounds the fan and turbine in larger commercial aircrafts is designed to prevent any debris to escape and damage any other systems such as fuel tanks or fuselage in the event that a blade should come off. This structure adds considerable bulk to the engine and because of the importance of the containment structure any redesign needs to be thoroughly tested. The high costs associated with containment testing means industry is looking into the feasibility of substituting parts of the expensive experimental testing with more economical numerical simulations. In this thesis modelling of the plastic behaviour of the nickel based super alloy, called Alloy 718, is investigated in an effort to correctly model the material in numerical simulations. This material is one of the most widely used materials in the parts of an aircraft engine subjected to elevated temperatures due to its retained strength and resistance to corrosion and creep. The material models chosen to model the plastic behaviour were the widely used Johnson-Cook and Zerilli-Armstrong models, because of their proven applicability for wide ranges of strain rates. The models were calibrated using data collected from tensile testing performed in a high speed VHS machine from Instron. Tensile tests were performed at quasi-static conditions and raised strain rates up to 1000 s-1. With an induction coil testing was also performed at temperatures up to 650 oC. Fitting the models to the data gave models valid from quasi-static to high rate conditions. In order to test the accuracy of the models they need to be validated. For this purpose a reverse impact experiment using free flying discs impacting a long slender rod was designed. This design enables the force history to be accurately monitored throughout the impact, while still achieving high strain rates. An investigation into producing additional data for use in validation was also performed. This investigation utilized a series of high speed photographs on which shape measurements were carried out in order to find parameters such as plate velocity and average strain without interfering with the experimental results
Godkänd; 2014; 20140115 (tedsjo); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Ted Sjöberg Ämne: Hållfasthetslära/Solid Mechanics Uppsats: Plasticity Modelling of Nickel Based Super Alloy Alloy 718 Examinator: Professor Mats Oldenburg, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Forskare Paul Åkerström, Swerea MEFOS Tid: Fredag den 28 februari 2014 kl 09.00 Plats: E246, Luleå tekniska

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Halpenny, Elizabeth A. "Environmental Behaviour, Place Attachment and Park Visitation: A case study of visitors to Point Pelee National Park." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/718.

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This thesis explores the relationship between place attachment and pro-environmental behaviour expressed by visitors to Point Pelee National Park. Place attachment, the functional, cognitive and emotional bond with a place, may play a role in promoting environmentally responsible behaviours. This may be especially true of place-specific pro-environmental behaviours; however place attachment may also have a "carry-over" effect in that its impact on individuals' self identity may also foster pro-environmental behaviour in individuals' every day lives.

An exploration of these relationships was achieved, first by measuring the intensity of place attachment and pro-environment behavioural intentions expressed by visitors to Point Pelee National Park. This was followed by an examination of the relationship between these two constructs using correlation analysis and structural equation modeling. Data was collected with a mail-based self-completed questionnaire. A quota sample of visitors to Point Pelee National Park was utilized. A response rate of 32% (n = 355) was achieved.

The relationship between place attachment and pro-environmental intentions was explored further through the measurement of several related variables. These factors include place satisfaction (based on an appraisal of nature, social and activity-based environments), motivation for visiting the park (related to social interaction and nature observation, as well as activity-based and learning opportunities), distance between the park and visitors' residences, membership in environmental organizations, and visitation patterns including visitation to the park during childhood, length of affiliation with the park, length of visit to the park, and frequency of visitation to the park. Theoretical and empirical research suggests that these factors may affect place attachment, pro-environment behavioural intentions, and/or the relationship between these two constructs.

Study results found positive associations between place attachment and all of these variables with the exception of visitation motives associated with learning and engaging in a favourite activity. The strongest predictive relationships were observed with anti-substitution (the inability of an individual to substitute the park for another destination because of a lack of resources such as time or money or a lack of awareness of comparable sites) followed by frequency of visits to the park; park commitment (based on Friends group membership and donations of time and money to the Friends group); Friends of Point Pelee (FoPP) membership; and park relationship (which was based on visitation to the park as a child and length of affiliation); and, satisfaction with the park.

Results support the proposition that place attachment has a strong positive association with both park-specific pro-environment behavioural intentions (e. g. , Write letters in support of Point Pelee N. P. and similar protected areas) as well as general pro-environment behavioural intentions (e. g. , Pay extra for transportation if it is environmentally-friendly). Place attachment strongly predicted park-specific, and moderately predicted general pro-environmental intentions. A number of other variables had an indirect effect on park-specific intentions; notable effects were demonstrated by frequency of visits; park relationship; visitation to the park as a child; place satisfaction; social satisfaction; FoPP membership; and, park commitment; anti-substitution. These affects were mediated by place attachment. After place attachment the strongest predictors of park-specific intentions were anti-substitution; frequency of visits; park commitment; and, general environmental commitment (which was based on membership in an environmental organization and donations of time and money to that organization).

Place attachment was not the only direct predicator of general pro-environmental intentions; general environmental commitment and membership in an environmental organization also directly predicted general pro-environmental intentions. Notable indirect effects, mediated by place attachment were produced by frequency of visits; park relationship; FoPP membership; park commitment; and anti-substitution. The strongest predictors of general pro-environmental intentions were general environmental commitment, followed by place attachment, membership in an environmental organization, and frequency of park visitation.

These findings correspond with much of the literature published on place attachment formation and the development of pro-environmental behaviours. The most notable contribution of this study is its comparison of place attachment's impact on general versus place-specific behaviours, and the role that several related variables play in this relationship.

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Heltsley, Rebecca. "Study of Polyaromatic Hydrocarbons Emitted in the Fly Ash from Coal Combustion in a Fluidized Bed Combuster." TopSCHOLAR®, 2000. http://digitalcommons.wku.edu/theses/718.

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Exposure to Polyaromatic Hydrocarbons (PAHs) has long been identified as an environmental concern because of their carcinogenic and mutagenic effects. The Environmental Protection Agency (EPA) has developed a list of 16 PAHs that are found on the Priority Pollutant List due to the extensive amount of data suggesting the hazards of these compounds. These toxic compounds are often emitted into the atmosphere by anthropogenic sources, such as combustors. Therefore, analysis of these compounds must be conducted during coal combustion. Two 1000-hour coal combustion burns were performed using the 0.1 MWth bench-scale fluidized bed combustor (FBC), which is found in the Combustion Laboratory at Western Kentucky University. The data contained in this thesis were collected from burning coal 97025 and coal 99626 for 1000-hour experiments. The fly ash produced from the combustor was examined as the media for the PAHs. It was collected by an in-situ cyclone sampler that was attached to various ports along the combustor during specific conditions in the combustor. Once the fly ash was collected it was analyzed with two different extraction methods. Solvent extraction was the first method used in this study. Dichloromethane was the solvent used to extract the PAHs in the fly ash. Once the extraction was completed, GC/MS in the selective ion monitoring (SIM) mode was used to analyze the extract. The other method used to extract the PAHs from the fly ash was the thermal extraction method. This method allows direct analysis of the PAHs without any use of a solvent. The GC/TOFMS was used to analyze the samples that were extracted by the thermal extraction method. In this study, the effects of combustion temperature, combustion bed height, sampling height, excess air ratio, and fluidizing velocity were examined to determine how each of these parameters affected the release of PAHs in the fly ash. The results indicated that the parameters investigated have a major influence on the production of PAHs in the combustor. As combustion efficiency decreases, larger PAHs (four to five fused rings) are detected in the fly ash; whereas, during high efficiency combustion, smaller PAHs (two to three fused rings) are more likely to be detected.

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Choy, Emmett. "Hong Kong's Economic Freedom and Income Inequality." Scholarship @ Claremont, 2013. http://scholarship.claremont.edu/cmc_theses/718.

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Hong Kong is considered to be the most economically free country in the world, but also has the highest amount of income inequality of any developed country. The Hong Kong government is able to sustain laissez faire policies due to its monopoly on land supply. Maintaining high property values allows the government to maximize revenue from property tax, which acts as a hidden tax. A major contributor to income inequality is the formation of oligopolies in Hong Kong that creates an anticompetitive environment. The interests of the government and oligarchs are aligned as both obtain significant portions of revenue from the property sector. As globalization makes Hong Kong even more vulnerable to external shocks, the government faces the challenges of increasing competition, diversifying its revenue streams, and closing the income gap while standing by its principles in order maintain regional competitiveness as an international business hub.

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Quintana, Ramírez Ana Patricia. "Conflicto por la gestión del servicio de acueducto en Dosquebradas (Risaralda-Colombia). Un estudio desde la ecología política, El." Doctoral thesis, Universitat de Barcelona, 2008. http://hdl.handle.net/10803/718.

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La investigación sobre el conflicto por la gestión del servicio de acueducto en Dosquebradas, es un estudio que aprovecha el enfoque ofrecido por la ecología política, para explicar la manera como en un municipio colombiano se presentan desacuerdos entre la administración municipal y las asociaciones de acueductos comunitarios para la solución del problema de desabastecimiento de agua potable para los habitantes pobres de la localidad.

Este conflicto ambiental aparece por la presencia principalmente de tres factores: En primer lugar, la urbanización del municipio de Dosquebradas en manos de particulares, sin control y orientación estatal obligó a los pobladores a construir sus propios sistemas de abastecimiento de agua potable. Se trata de asentamientos periurbanos, en muchos casos sin licencias ni permiso de urbanismo, que convirtió el territorio biquebradense desde 1948 en una feria de predios. Como consecuencia de ello, una gran proporción de urbanizaciones se han construido sin garantía de acceso a los servicios públicos de agua.

En segundo lugar, esta situación se ha dado en el marco de unas políticas ambientales y de servicios públicos municipales, regionales y nacionales que han favorecido progresivamente la mercantilización del sector en general y del servicio público en particular, y su traspaso a manos de actores privados o empresas mixtas. Con ello, se debilitó la responsabilidad estatal en la prestación de los servicios públicos a la población más pobre.

Estos dos antecedentes, contrastaron con un modelo de gestión colectiva del servicio de acueducto, que en Dosquebradas comenzó desde 1925. Para los habitantes de diferentes zonas de Dosquebradas, la autogestión fue y continúa siendo la solución más efectiva para cubrir muchas de sus necesidades básicas como apertura de brechas, caminos, vías y saneamiento básico, construcción de acueducto y alcantarillado. Sin embargo, este modelo de gestión colectiva se debilitó a medida que parte de los líderes de las Juntas de Acción Comunal y de las Asociaciones de acueductos comunitarios, ante la urgencia por satisfacer las múltiples necesidades de los pobladores pobres a quienes representaban y mantener las infraestructuras necesarias para garantizar el servicio de acueducto a mayor número de habitantes, se articularon a redes clientelares de políticos que ofrecían solución a las demandas de la población en épocas electorales, para luego generalmente incumplirlas durante el desarrollo de la gestión pública. A cambio de ello, los directivos redujeron la autonomía política que caracteriza al modelo de gestión colectiva del agua, ya que su gestión para sostener la infraestructura dependió en algunos casos de promesas irresueltas por parte de los políticos de turno.

El conflicto ambiental que afronta hoy el municipio de Dosquebradas contrapone a distintos prestadores que gestionan el servicio de acueducto, a la sociedad civil y las instituciones públicas, y se manifiesta como una competencia entre dos modelos de prestación del servicio público de agua potable, el estatal-empresarial y el colectivo. Cada uno de estos modelos supone esquemas distintos de propiedad de la infraestructura, de administración y de organización social. Se encuentra conectado con una problemática más global de confrontación por el manejo y la administración de los recursos naturales, que forma parte del proceso de mercantilización y privatización del agua y los servicios públicos en Colombia, América Latina y el mundo.

NOTA BENE: En la actualidad, la autora es docente de la Universidad Tecnológica de Pereira.
The research about the Dosquebradas conflict for management aqueduct service to be considering from theory politics ecology, for to explain in a Colombian municipality the way disagreement between city hall and community aqueduct association for solution the abasto problem the potable water for poor resident of this locality.

This environmental conflict emerges because: one, the particular cultural and socio-politics characteristics of housing development. The private person has had responsibility of housing development and the poor person was not having aqueduct service. It neither has had state control. Two, the politics environmentalist and public's services municipal, regional and national has evolution for privateers. Three, the collective systems of administration for abasto of water was debilitate.

The environmental conflict of Dosquebradas is principality one confrontation between civil society and public's institution, one competition between the state model and collective model for to pay attention the public's services. Each model has different types of infrastructure property, administration and social organization. The environmental conflict of Dosquebradas is communicate with the grown-ups problems is concerned to negotiations of natural resources, also with the water privatization, as well with to attend public's services for poor people in Colombia, Latin America and the world.

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31

Bishop, Jonathan R. B. "Embedding population dynamics in mark-recapture models." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/718.

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32

Le, B. Khanh. "Capabilities, labor participation, and women's freedom a discourse on the relation between paid employment and female agency /." Diss., Connect to the thesis, 2005. http://hdl.handle.net/10066/718.

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33

Trudinger, Dave. "The Comfort of Men: A Critical History of Managerial and Professional Men in Post-war Modernisation, Australia 1945-1965." University of Sydney. History, 2004. http://hdl.handle.net/2123/718.

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This thesis is a critical history of managerial and professional men in post-Second World War Australia. The attention that I have given managerial and professional men has been determined by my own political desire to problematise the continued accomplishment of hegemony. As subjects, these men and their discursive practices enable scrutiny of the regenerative labour necessary to sustain power and necessary to realise the material results that accrue to those performing such work. My thesis examines the practices of particular groups of managerial and professional men within four discrete social settings or terrain during the post-war period. I interrogate the operations of managerial and professional men in personnel management (the terrain of work), in market research (the terrain of the market), in parenting and marriage guidance (the terrain of the family) and in the service club Rotary (the terrain of the civic). In each of these terrains I find managerial and professional men framing problems and enacting solutions. A process or intervention that makes natural the connections of interest (of advantage or disadvantage) being constantly recreated; an intervention that expresses a comfort with the mechanics and entailments of hegemony. To enable my critical history I apply, in each terrain, a framework comprising three core elements. I historicize the accomplishment of hegemony; testing the emergence of government and positive expressions of power during post-war modernisation in the local contexts of managerial and professional men�s interventions. I people hegemony; identifying the practices of managerial and professional men as resources for doing social relations (in particular the relations of gender and class) and crucial to the operation of hegemony. And, thirdly, I demonstrate the interventions of these men to be interested; unravelling the possessive investments managerial and professional men make through their interventions. My scrutiny of managerial and profession men and their practices, my choice of terrains in which to study them, my analysis of the process enacted in these terrain and the sources that I have utilised are not intended to assemble a biography of men�s experiences or ideal masculinities. Rather, my thesis provides a biography of interventions in order to disassemble that which appears not to be anything in particular: the ordinary regeneration of hegemony by ordinary men doing ordinary things.

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Tranberg, Mattias. "N-acetylaspartate in brain : studies on efflux and function /." Göteborg : Institute of Neuroscience and Physiology, Department of Physiology, The Sahlgrenska Academy, Göteborg University, 2006. http://hdl.handle.net/2077/718.

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35

Majumder, Mainak. "Molecular transport properties through carbon nanotube membrane." Lexington, Ky. : [University of Kentucky Libraries], 2007. http://hdl.handle.net/10225/718.

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Thesis (Ph. D.)--University of Kentucky, 2007.
Title from document title page (viewed on March 25, 2008). Document formatted into pages; contains: xxii, 203 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 183-201).

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Elmughrabi, Awad Elsaber. "Measurement and modelling of the fire behaviour of composite laminates." Thesis, University of Newcastle Upon Tyne, 2008. http://hdl.handle.net/10443/718.

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This thesis describes the measurement and modelling of the fire reaction and resistance properties of fibre glass polyester and vinyl ester composite laminates. A new small-scale loading frame was designed and fabricated to apply tensile and compressive stresses in a cone calorimeter under a constant heat flux of 75 kW/m2. It was found, for the first time, that stress has a small but significant effect on the fire reaction properties. Increasing tensile stress increased heat release rate and smoke production, while shortening the time-to-ignition. Compressive stress had the reverse effect. This was attributed to the fact that tensile stress promotes the formation of matrix microcracks, facilitating the evolution of flammable volatiles. This hypothesis is further supported by the observation that stress has the greatest effect on the early heat and smoke release peaks, with a lower effect on the final `run-out' values. Another new small scale testing rig was developed along with a calibrated conical radiant heater, which resembles the cone calorimeter's heater, to allow testing composite laminates at high tensile and compressive stresses. Stress rupture (time-to-failure) curves were produced. It was shown that, in tension, the behaviour was fibre dominated, with failure times roughly ten times those in compression. Compressive failure involved resin dominated local fibre kinking initiated near the cold face and was controlled by the matrix glass transition temperature. The existing thermal model was upgraded to include the mass flux effect into the net total energy on the hot face of the composite laminate at flashover. This novel approach has resulted in very good predictions of the most important fire reaction properties obtained from the cone calorimeter such as time-to-ignition, mass loss rate, heat release rate and flame-out time. In addition, the predicted temperature and resin content profiles combined with the temperature dependent properties values were used to model the failure times by applying a suitable empirical relationship. Good agreement was found.

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Johng, Breeana J. "A Mathematical Model of the Effect of Aspirin on Blood Clotting." Scholarship @ Claremont, 2015. http://scholarship.claremont.edu/scripps_theses/718.

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In this paper, we provide a mathematical model of the effect of aspirin on blood clotting. The model tracks the enzyme prostaglandin H synthase and an important blood clotting factor, thromboxane A2, in the form of thromboxane B2. Through model analysis, we determine conditions under which the reactions of prostaglandin H synthase are self-sustaining. Lastly, through numerical simulations, we demonstrate that the model accurately captures the steady-state chemical concentrations of interest in blood, both with and without aspirin treatment.

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Brett, Richard Francis. "Flexible staffing solutions and its impact on customer satisfaction / Richard Francis Brett." Thesis, North-West University, 2007. http://hdl.handle.net/10394/718.

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The face of the workplace has changed dramatically over the past decade and most organisations have to survive in a fiercely competitive global economy. The impact of the competitive changes, especially in the service environment has become critical and quality service is considered an essential strategy for success and survival in today's competitive environment. Organisations are continuously searching for ways to improve their performance and create a sustainable competitive advantage. Consumers are also continuously being made more aware of their rights and in today's fast paced world, with time constraints and increased stress, tolerance levels have been considerably eroded. In view of this, customer satisfaction has become a focus area, in particular, to investigate ways that it can be enhanced to gain a competitive edge. A better understanding of how organisations can apply resources to achieve these goals will be a useful instrument towards gaining sustainable competitive advantage. One way of doing this is for service firms to manage their capacity to achieve maximum and/or optimum utilisation at all times, if possible. But having trained staff on hand at the right times is no easy task. Overstaffing can lead to budget blow-out, while understating adds to staff stress levels, and can contribute to both customer and staff dissatisfaction. As a possible solution many employers tackle this problem by employing casual staff who are more flexible in their working hours and can be deployed to meet peak demands in service. The objective of this study was to investigate the importance of customer satisfaction and whether the utilisation of temporary staffing solutions could positively contribute in improving service levels. A survey research design was used with a questionnaire as data-gathering instrument. The study population consisted of customers (N=507) that visited Absa branches in the Vaal Triangle and were serviced by either permanent or flexi tellers. Contingency tables were used to record and analyse the relationship between the different variables, and statistical significance tests were used to show that the results are significant. Chi-square and Cramer's phi or V test were used as the basis of the analysis. The research confirmed that customer satisfaction has definite financial benefits for an organisation and that the effective application of temporary staffing solutions could further enhance these benefits. The results of the statistical analysis of the survey further confirmed that there was no significant difference in the perceived level of service received from either permanent or flexi tellers. Limitations in the research are identified and recommendations for future research are made.
Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2008.

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39

Stewart, Michael Andrew. "Sound transmission through a chipboard floating floor supported on a concrete slab." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/718.

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Lol, Wilford Gibson. "An investigation of the impact of routing protocols on MANETs using simulation modelling a dissertation submitted to Auckland University of Technology in partial fufilment of the requirements for the degree of Master of Computer and Information Sciences, 2008 /." Click here to access this resource online, 2008. http://hdl.handle.net/10292/718.

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Thesis (MCIS - Computer and Information Sciences) -- AUT University, 2008.
Includes bibliographical references. Also held in print ( xi, 105 leaves : ill. ; 30 cm.) in the Archive at the City Campus (T 621.382 LOL)

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Swart, Morne. "Synthesis and characterization of electrospun organic-inorganic hybrid graft copolymer nanofibers of poly(methyl methacrylate) and polydimethylsiloxane." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/718.

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42

Nelson, Faye. "A Qualitative Study of Effective School Discipline Practices: Perceptions of Administrators, Tenured Teachers, and Parents in Twenty Schools." Digital Commons @ East Tennessee State University, 2002. https://dc.etsu.edu/etd/718.

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Many educators and parents are gravely concerned about disorder and danger in school environments. In addition to school discipline issues, American classrooms are frequently plagued by minor infractions of misbehavior that disrupt the flow of classroom activities and interfere with learning. The purpose of this qualitative study was to investigate common threads of effective school discipline practices as perceived by administrators, tenured teachers, and parents in 20 schools in East Tennessee. I also attempted to determine if the views of administrators, tenured teachers, and parents are consistent with published research on school discipline practices. Data were collected from administrators, tenured teachers, and parents through an open-ended interview form that I designed. The study offers a number of recommendations regarding components of effective school discipline practices. An effective school discipline practice involves all stakeholders in its design. The principal and the teachers are responsible for carrying out the school discipline practices to foster appropriate behavior from the students. However, parents, students and community members should be equally represented in the design of discipline procedures. Administrators and teachers need to have quality professional development opportunities to acquire strategies for classroom and school discipline practices. Rewarding students for good behavior and positive contributions to the school community is important. Effective discipline practices are built through consistency and teamwork. Evaluation of school discipline practices should be ongoing, and strategies for reducing school disruptions should be continuously assessed for improvements.

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Matos, Aldinelle Fontenelle de. "A formação continuada de professores auxiliando na construção de projetos científicos para feiras de ciências." reponame:Repositório Institucional da UNIVATES, 2014. http://hdl.handle.net/10737/718.

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O presente estudo é resultado da investigação realizada a partir de uma intervenção pedagógica com um grupo de cinco professores que ministram aulas na segunda etapa do Ensino Fundamental, no Estado de Roraima. O problema central está em detectar em quais aspectos as atividades desenvolvidas em um curso de formação continuada de professores, com foco na elaboração de Projetos Científicos, podem auxiliar na melhoria da construção de Projetos em uma Feira de Ciências na escola. Como objetivo geral propôs-se investigar como a formação continuada de professores pode auxiliar os docentes na elaboração de Projetos Científicos. O referencial teórico segue pressupostos que abordam a formação continuada, Feira de Ciências, Projetos Científicos e interdisciplinaridade. A metodologia utilizada para realizar o estudo foi de cunho qualitativo com foco na pesquisa-ação. A coleta de dados foi realizada por meio de três questionários aplicados antes, durante e depois do curso de formação, compostos de perguntas abertas e fechadas; transcrições de filmagens e diário de campo. Na análise de resultados, foi possível verificar que o curso de formação continuada de professores trouxe mudanças para a comunidade escolar, pois, na Feira de Ciências de 2014, quatro projetos orientados pelos professores que participaram do curso foram selecionados para a Feira Estadual. Tendo em vista que as mudanças no setor educacional não acontecem repentinamente, mas sim, gradativamente, acredita-se que mudanças mais significativas nessa comunidade ainda estão por vir.
The present project is the result of research conducted from a pedagogical intervention with a group of five teachers who teach classes in the second stage of elementary school, in the State of Roraima. The central problem is to detect in which aspects the activities developed in a course of continuing education of teachers, with a focus on the development of Scientific Projects, may assist in improving the construction of projects in a science fair at school. As a general purpose set out to investigate how the continuous formation of teachers can assist teachers in developing Scientific Projects. The theoretical assumptions that address follows the continuing education, science fair, science projects and interdisciplinarity. The methodology used to conduct the study was qualitative oriented with focus on researchaction. The data were collected through three questionnaires applied before, during and after the course of training, open and closed questions compounds; transcripts of filming and field journal. In the analysis of results, it was possible to verify that the course of continuous formation of teachers brought changes to the school community, because, at the science fair for 2014, three projects guided by teachers who participated in the course were selected for the State fair. Considering that the changes in the educational sector do not happen suddenly, but gradually, it is believed that the most significant changes in this community are still to come.

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44

Cameron, Allan Walter. "How perceptions of autonomy affect suburban elementary school teachers’ perceptions of efficacy regarding state-mandated testing." Thesis, Boston College, 2008. http://hdl.handle.net/2345/718.

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The No Child Left Behind Act directs states to establish annual assessments to measure student mastery of state-established learning expectations. American public school students in grades 3 through 8, with few exceptions, take a series of state-mandated assessments each year; students in grades 10 through 12 take a series of state-mandated assessments at least once during those years. NCLB and state laws mandate considerable consequences if students do not perform well on the assessments. Research suggests that the standardized tests associated with NCLB affect curricula and pedagogy. What is not known is the level of control teachers believe they have over the curricular and pedagogic changes, and how that level of perceived control affects teachers’ perceptions of their ability to prepare students for the state-mandated tests. The purpose of this research study was to examine how teachers’ perceptions of autonomy affect their perceptions of efficacy regarding state-mandated testing. Data were collected with the Teaching Autonomy Scale (Pearson & Hall, 1993) and follow-up interviews with teachers from a suburban Connecticut public school district. The findings of the study suggest that teacher perceptions of autonomy do not significantly affect their perceptions of efficacy regarding the state-mandated tests associated with NCLB. The findings also suggest that teacher perceptions of autonomy do affect how teachers view the state-mandated standardized tests. Teachers with high perceived autonomy tended to report that the state-mandated tests had less of an impact on their classroom practices; had some discretion regarding how to use curricular materials in their classes; said that their students performed well on the state-mandated tests because the students engaged in authentic learning exercises that taught the students the skills and concepts assessed by the tests; tended to view the state-tests as assessments of the reading, writing, and math curricula; and tended to report that the state-mandated tests had mostly positive effects on education. Implications for practice, public policy, and further research are presented
Thesis (PhD) — Boston College, 2008
Submitted to: Boston College. Lynch School of Education
Discipline: Educational Administration and Higher Education

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45

Holbrook, Ebrahim Christine. "The Use, Beliefs, Perceived Barriers, and Methods of Delivery of Play Therapy by Elementary School Counselors." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/718.

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Mental health problems can interfere with a child's ability to succeed in school (Hootman, Houck, & King, 2003) and ultimately increase the risk of family dysfunction, drug abuse, juvenile incarcerations, and school drop out (American Academy of Pediatrics, 2004). Because young children often lack the verbal skills needed to communicate anxieties or fears and because children naturally communicate through the use of play, elementary school counselors realize that play therapy is an appropriate alternative to talk therapy (Landreth, 2002). Although recent studies have demonstrated the efficacy of play therapy with elementary school students suffering from conduct disorders (Cochran & Cochran, 1999), autism, obsessive compulsive disorder, attention-deficit/hyperactivity disorder, cerebral palsy (Johnson, McLeod, & Fall, 1997), post traumatic stress disorder (Shen & Sink, 2002), and children at risk (Post, 1999), no studies have examined the specifics of how elementary school counselors who utilize play therapy deliver it to their students. The purpose of this study was to examine the use, beliefs, perceived barriers, and methods of play therapy delivery by elementary school counselors. Additionally, this study examined the methods used to overcome barriers to implementing play therapy. While the elementary school counselors surveyed in this study seem to agree that play therapy is useful to their students, and an overwhelming majority use it (78.8%), roughly half had not received any formal play therapy training. Several barriers to implementing play therapy were identified including a lack of time, space, training, resources, and support and/or understanding from parents, teachers, or school administrators. Participants discussed the methods they use to overcome barriers, such as buying their own play therapy materials and educating faculty and parents about the positive effects of play therapy through the use of newsletters, brochures, and bulletin boards. Respondents used over 30 different play therapy techniques; the three most utilized techniques were drawing, board games, and role play. Implications for elementary school counselor practice and training were given, as well as implications for future research.

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46

Wong, You Liang Lionel. "Piezoelectric Ribbons for Stretchable Energy Harvesting." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/718.

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As we enter the age of the internet of things (IoT), more embedded devices are appearing in our everyday items, such as electrical appliances, watches, mobile phones, and even clothes. These are devices that are able to communicate with one another and collect sensing data about their environment. An emerging area of interest in this field is the wearable devices, such as smart devices for healthcare and wellness implantables. These devices require power and batteries will need to be constantly recharged, adding to the users’ inconvenience. Energy harvesters are devices that are able to harness ambient energy such as movement and convert it into useful electrical energy. As such, energy harvesters are expected to play an important role in powering such devices in order to save space and more importantly to increase the comfort and convenience of the users. This work presents a piezoelectric energy harvester that captures energy from stretchable surfaces such as the human skin, exterior of organs and even garments. The main feature of the harvester is the inclusion of a ribbon structure encased in a flexible elastomer, Ecoflex. This allows the device to stretch to tens of percents, while maintaining strain levels of the piezoelectric material within its mechanical limits, which is required since stretchable surfaces can strain to tens of percent. This device provides an efficient method of converting overall device stretch to bending stress within the piezoelectric material, and can strain both horizontally and vertically. Polyvinylidene fluoride (PVDF) and its copolymer, polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) are the material of choice due to their flexibility and magnitude of piezoelectric coefficients. A thickness of 10-28 μm is chosen for the PVDF film and the total device thickness including the Ecoflex ranges from 1-3 mm. Bimorph structure and alternately-connected electrodes ensure that charge cancellation is minimized. Static and transient finite element modeling are carried out to characterize the devices and obtain trends for design parameters. The trends obtained will allow the user to select device parameters given certain constraints such as film thickness and device effective Young’s modulus. Two fabrication approaches are used to fabricate planar PVDF, PVDF-TrFE films. The first approach involves fabricating the film starting from PVDF-TrFE powder. The powder is dissolved in a solvent and cast using an in-house stainless steel structure onto a wafer that has spincast gelatin. Gelatin acts as a release layer. Aluminum and chromium are sputtered and patterned on the wafer before a second layer of PVDF-TrFE is cast again. A top metal is then patterned and a method to etch the PVDF-TrFE is developed in order to access the bottom metal. Each PVDF-TrFE layer is 10 μm thick. To ensure that the electrodes are flexible, mesh designs are incorporated. Various measurements such as mechanical, ferroelectric and piezoresponse measurements are carried out to verify the performance of the film. The second approach uses commercial PVDF film of 28 μm, with 6 μm of silver ink as the electrodes. These silver ink allows for the metal to stretch to 10% and the mesh design is not needed. Two types of patterning the metal are devised. One method involves using a laser cutter to define the shape of a label, which then acts as a mask. Another lithographic method has been devised in order to accurately define the patterns. This method involves temporarily bonding the film to a wafer and using dry film photoresist. Top and bottom side metal alignment is carried out using backside alignment option of the photolithography tool. With the planar films, a molding method is then developed in order to mold the film into the required ribbon shape. This method involves 3D printing various assembly rigs in order to achieve the desired final shapes. A snap-in locking mechanism has also been devised to enable self-alignment of the film to the mold, which is difficult to achieve on device patterns smaller than 500 μm radius. Ecoflex is used as the elastomer since this material can stretch to 400%. Three device sizes, namely 350, 500 and 750 μm radius devices are fabricated in order to have different devices for comparison with respect to scaling of the design. These devices are able to stretch up to 40%, while still maintaining structural integrity. The 350 μm device is able to generate 292 nW of power for an active volume of 0.387 cm3 when stretched 20%. This energy density is similar to other devices, albeit being able to strain at a much higher overall level. Finally, various extensions of the harvester are explored to provide an overview of the possible future work for the harvester.

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47

Klinka, Karel, Jaume Fons, and Christine Chourmouzis. "Nutrient and biotic properties of mormoder and leptomoder humus forms in the coastal western hemlock zone." Forest Sciences Department, University of British Columbia, 1997. http://hdl.handle.net/2429/718.

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In British Columbia, humus form identification is widely use to infer the level of plant-available soil nutrients. This identification is based on field-observable (morphological) features. We recognize three major humu forms: Mors, Moders, and Mulls - which are differentiated according to the type of F horizon, and the presence/absence of organic matter-enriched Ah horizons. Mors represent humus forms where decomposition is dominated by fungi, with slow decomposition rates and accumulations of organic matter on the soil surface. Mors are characterized by the presence of a Fm (m - mycogenous) horizon. In contrast, Mulls represent humus forms with high rates of decomposition and faunal activity resulting in organic matter being intimately incorporated into the upper mineral soil layer instead of accumulating on its surface. Intermediate on the humus form gradient from Mors to Mull are the Moders. Moders are similar to Mors in that they have accumulations of organic matter on the surface of the mineral soil but decomposition is not fungus dominated, so they lack the diagnostic Fm horizon. The central concept of the Moder is represented by the Leptomoder, which is characterized by a Fz (z - zoogenous) horizon with an active population of soil meso- and microfauna, fungal mycelia are not present or present in small amounts. When both fungal mycelia and faunal droppings can be found, but neither clearly predominate over the other, an Fa (a - amphimorphic) horizon results. Fa horizons are characteristic of Mormoders, an integrade between Mors and Moders. Considering the prevalence of Mormoders and Leptomoders in B.C. and the difficulties in identifying Fa horizons, the aim of this study was to determine whether the morphological features used to differentiate these two Moder humus forms reflects differences in their physical, chemical and biotic properties.

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Lim, Sokchea. "ESSAYS ON A SMALL OPEN ECONOMY WITH CROSS-BORDER LABOR MOBILITY." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/718.

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The dissertation examines the macroeconomic impact of fiscal policy, including a recently-debated remittance tax in a small open economy that exports migrant workers and, at the same time, receives remittances sent by those migrants to families in the home country. The research also investigates the responses of optimal fiscal policy to shocks in either the home or the host country. Then, the empirical exercises are performed to determine the motivations behind remittances. More specifically, we test whether remittances come from existing migrants or result from migration when families at home experience income contraction caused by weather or natural disaster shocks. Chapter 1 provides some interesting findings. First, the results show that an economy with international migration is more resilient to demand shocks resulting from fiscal contraction. Second, the short-run association between remittances and domestic output depends on the sources of the shocks. Third, our results indicate that the equilibrium impact of a tax on remittances can be expansionary and welfare-improving when an economy is initially close to full employment. The presence of utility-enhancing government expenditures and a potential negative externality from over-allocation of labor abroad (over migration) justify the presence of distortionary taxes. Chapter 2 shows that an increase in remittances due to shocks in the host country increases consumption, but reduces domestic output due to labor migration. In such a case, optimal fiscal policy responds by lowering taxes on factor incomes to encourage domestic labor participation and increasing the remittance tax to curb labor migration. However, optimal policy response to shocks in the domestic economy is to raise all income taxes including factor incomes and remittances. Chapter 3 shows that there is no evidence that supports pure altruism hypothesis. Specifically, home income contraction due to natural disasters or weather shocks does not appear to induce existing migrants residing abroad to send more remittances. However, the results indicate that remittances increase as people experiencing the income shocks migrate to earn higher income abroad. The findings support our theoretical specification in the previous chapters that links remittances to international migration.

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Zargham, Emilia Ohsone. "INVESTIGATIONS OF BINDING TARGETS OF THE PRO-MUTAGEN 2-AMINOANTHRACENE IN FISCHER-344 RATS." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/718.

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Environmental exposures causing ingestions of toxic chemicals, such as the polycyclic aromatic hydrocarbon 2-aminoanthracene (2-AA), may increase the risk of developing cancer and other diseases such as diabetes. To understand the mode of action of 2-AA as it relates to diabetogenic processes and pancreatic cancer, 2-AA binding to soluble protein mixtures was investigated using a novel technique called dynamic isoelectric anisotropy ligand binding assay (DIABLA). Twenty four post-weaning 3-4 week old Fischer-344 (F-344) male rats were fed 0 mg/kg (control), 50 mg/kg (low dose), 75 mg/kg (medium dose) and 100 mg/kg (high dose) 2-AA diet for 14 and 28 days. Total proteins extracted from the pancreas and liver were evaluated for their binding potential using DIABLA. This technique utilizes capillary isoelectric focusing and fluorescence anisotropy to separate proteins in their active form as well as evaluate the chemical interactions. Isoelectric point (pI) values for protein binding as well as experimental mass spectra data were determined. Investigation of 2-AA binding through screening a complex mixture of proteins is a step towards understanding the mode of action and the biological activities.

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Sarrabayrouse, Guillaume. "Rôle régulateur des protéines Rho dans la réponse immune anti-mélanome." Toulouse 3, 2007. http://thesesups.ups-tlse.fr/718/.

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Les stratégies d'immunothérapie sont basées sur l'existence d'antigènes de tumeur (TAA) contre lesquels l'hôte est capable d'induire une réponse immune spécifique. Cependant, les cellules tumorales sont souvent peu immunogènes à cause de leur faible densité en complexes CMH de classe I (CMH-I)/TAA ou à cause de leur incapacité à délivrer des signaux de costimulation. Au cours de ce travail, nous avons mis en évidence, que l'inhibition de la géranylgéranyl transférase I par le GGTI-298 favorise l'induction d'une réponse immune anti-mélanome, en induisant, sur les cellules tumorales murines B16F10 traitées, une expression des molécules de costimulation (CD80 et CD86) et une surexpression des molécules du CMH-I, induite par l'INF-gamma. Ces modifications permettent de favoriser le rejet immun des mélanomes traités injectés à des souris immunocompétentes et induisent chez ces souris l'activation de lymphocytes T spécifiques. Comme différentes petites protéines G de la famille Rho peuvent être géranylgéranylées, l'utilisation d'inhibiteurs spécifiques des protéines Rho (Rho A, Rho B et Rho C) a montré leur(s) implication(s) dans ces régulations. Ainsi, le traitement in vitro des cellules mélaniques murines par la combinaison d'INF-gamma et d'inhibiteurs des protéines Rho (C3 exoenzyme) induit une forte surexpression des molécules CMH-I et des molécules de costimulation CD80 et CD86 à la membrane des cellules tumorales. Par ailleurs, nous avons évalué l'intérêt thérapeutique de nos raitements pharmacologiques associant l'IFN-gamma et le GGTI-298. Nous avons dans un premier temps testé le potentiel vaccinal de nos traitements en montrant que des souris injectées avec des cellules B16F10 préalablement traitées et iradiées étaient partiellement protégées contre le développement de tumeurs sauvages. Dans un deuxième temps, nous avons montré que ces traitements induisent sur des tumeurs humaines une surexpression des molécules HLA de classe I et des molécules de costimulation ayant des activités activatrices (CD86) ou inhibitrices (PD- L1) et provenant des familles B7 ou TNF/TNFR. De plus, nous avons mis en évidence la capacité stimulatrice de ces mélanomes humains prétraités à induire in vitro l'activation de lymphocytes T CD8 cytotoxiques spécifiques des mélanomes et sécrétant de l'IFN-gamma, à partir de donneurs sains HLA-compatibles. .
Melanoma is a highly lethal cutaneous tumor, killing affected patients through multiple, poorly immunogenic metastases. Suboptimal activation of T lymphocytes by melanoma cells is often due to the defective expression of class I major histocompatibility antigens (MHC-I) and costimulatory molecules, or to the capacity of FasL molecules expressed on melanoma cells to induce lymphocyte apoptosis. In this work, I demonstrated that statins, inhibitors of HMGCoA reductase, enhance mIFN- gamma induced expression of MHC class I antigens on murine B16F10 melanoma. GGTI- 298, a geranylgeranyl transferase I inhibitor, mimics this effect of statins that is related to peptide transporter protein TAP1 up-regulation. Simultaneously, GGTI-298 induces the expression of CD80 and CD86 costimulatory molecules. C3 exoenzyme, which selectively inactivates Rho proteins, phenocopies the effects of GGTI-298, indicating a role for Rho proteins in these events. Furthermore, the treatment of B16F10 cells with GGTI-298 or C3 exoenzyme associated with mIFN-gamma induces in vivo tumor growth slowing down in immunocompetent but not in nu/nu syngeneic mice. Both in vivo injections and in vitro restimulation of splenocytes with GGTI-298- and mIFN-gamma-treated B16F10 cells induces an enhancement of specific CD8 T lymphocytes labeled by TRP-2/H-2K(b) tetramers. Using a human melanoma model (LB1319-MEL), we demonstrated that in vitro treatment with hIFN-gamma and GGTI-298 led to the up regulation of MHC-I and a costimulatory molecule CD86 and down regulation of an inhibitory molecule PD-1L. Co-culture experiments with peripheral blood mononuclear cells (PBMC) revealed that modifications induced by hIFN-gamma and GGTI- 298 on the selected melanoma cells, enables the stimulation of lymphocytes from HLA compatible healthy donors. Indeed, as compared with untreated melanoma cells, pretreatment with hIFN-gamma and GGTI-298 together rendered the melanoma cells more efficient at inducing the: i) activation of CD8 T lymphocytes (CD8+/CD69+); ii) proliferation of tumor- specific CD8 T cells (MelanA-MART1/TCR+); iii) secretion of hIFN-!; and iv) anti-melanoma specific cytotoxic cells. In this study, it is shown that vaccination with mIFN-gamma and GGTI-298 pretreated B16F10 cells induces a protection against untreated tumor growth and pulmonary metastases implantation. Furthermore the capacity of FasL molecules expressed on melanoma cells to induce lymphocyte apoptosis contributes to either antitumor immune response or escape depending on their expression level. .

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