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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Beschleunigte Alterung von Glasfasern in alkalischen Lösungen: Einflüsse auf die mechanischen Eigenschaften

Scheffler, Christina, Förster, Theresa, Mäder, Edith 03 June 2009 (has links) (PDF)
In alkalischen Lösungen führt die Reaktion von Hydroxylionen mit den Si-O-Si-Bindungen des Glasnetzwerks zur Bildung hydratisierter Oberflächen und gelöstem Silikat. Der Grad der Korrosion bzw. der Alterung der Glasfaser ist abhängig von der chemischen Zusammensetzung des Glases und Korrosionslösung sowie von Zeit und Temperatur. Die Untersuchung von Glasfasern verschiedener chemischer Zusammensetzung in NaOH- sowie Zementlösungen zeigte, dass die inhibierende Wirkung von Ca-Ionen zu einem veränderten Korrosionsmechanismus führt. Dies konnte anhand der mechanischen Eigenschaften der Glasfasern sowie rasterelektronenmikroskopischen Untersuchungen gezeigt werden. Während die Korrosion in NaOH-Lösung zu einer ausgeprägten Umwandlung der gesamten äußeren Glasfaserschicht in Reaktionsprodukte führte, zeigten Glasfasern in Zementlösung bei gleichem pH-Wert einen stark lokal begrenzten, punktförmigen Angriff. Daraus resultieren unterschiedliche mechanische Eigenschaften der Glasfasern in Abhängigkeit von der gewählten Korrosionslösung.
182

Investigation on jute fibres and their composites based on polypropylene and epoxy matrices / Untersuchungen zu Jutefasern und ihren Verbunden mit Polypropylen-und Epoxidharz-Matrizes

Doan, Thi Thu Loan 01 May 2006 (has links) (PDF)
- Matrix modification of jute/polypropylene composites with MAHgPP - Fibre surface modification for epoxy/jute composites, including: NaOH treatment, silane coupling agents, epoxy dispersion and their combinations - Investigation the influence of modification on the performance of jute fibre and jute compostites. / Untersuchungen zum mechanischen und thermischen Verhalten sowie zur Benetzung von Jute­fasern im Ausgangszustand, nach Entwachsen und nach Oberflächenmodifikation, mit dem Ziel einer Verwendung als Verstärkungsfasern in Verbundwerkstoffen. Untersuchungen zum mechanischen und thermischen Verhalten sowie zur hygrothermischen Alterung von Jute/Polypropylen (PP) Verbunden. Einfluss des PP-Typs, der Modifizierung der Matrix mit Maleinsäureanhydrid gepfropftem PP und des Faservolumengehalts.Untersuchung der Grenzschicht in Jute/Epoxidharz Verbunden in Hinblick auf die mechanischen Eigenschaften nach Alkalibehandlung und Oberflächenmodifikation der Jutefasern. Jutefasern haben gute spezifische mechanische Eigenschaften. Die Einzelfasereigenschaften unterliegen der bei Naturfasern üblichen Streuung der mechanischen Eigenschaften. Im Gegensatz zu konventionellen Verstärkungsfasern (Glas, Carbon) nimmt wachstumsbedingt mit zunehmendem Faserquerschnitt die Festigkeit tendenziell zu. Faseroberflächenbehandlungen verbessern die Benetzbarkeit, erhöhen die thermische Stabilität und reduzieren die Feuchteaufnahme sowie den Diffusionskoeffizient. Jute/Polypropylen-Verbunde Chemische und physikalische Wechselwirkungen zwischen Faser und MAHgPP nach optimierter Kopplerauswahl verbessern in Abhängigkeit vom PP-Typ die Grenzflächenscherfestigkeit und die mechanischen Eigenschaften. Durch Einbeziehen der Grenzflächeneigenschaften können mit einer modifizierten Mischungsregel die Zugfestigkeiten der Verbunde beschrieben werden. Jute/Epoxidharz-Verbunde Faseroberflächenbehandlungen mit Natronlauge, Organosilanen, Epoxiddispersionen und deren Kombinationen führen zu verbesserter Benetzung, reduzierter Wasseraufnahme und verbesserter Haftung sowie verbesserten mechanischen Eigenschaften in Jute/Epoxidharz-Verbunden.
183

An Experimental Study of Submerged Entry Nozzles (SEN) Focusing on Decarburization and Clogging

Memarpour, Arashk January 2011 (has links)
The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mould. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. In addition, the steelmaking processes occur at high temperatures around 1873 K, so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during preheating and casting processes is necessary for the design of the steelmaking processes  The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. A large number of accretion samples formed inside alumina-graphite clogged SENs were examined using FEG-SEM-EDS and Feature analysis. The internal coated SENs were used for continuous casting of stainless steel grades alloyed with Rare Earth Metals (REM). The post-mortem study results clearly revealed the formation of a multi-layer accretion. A harmful effect of the SENs decarburization on the accretion thickness was also indicated. In addition, the results indicated a penetration of the formed alkaline-rich glaze into the alumina-graphite base refractory. More specifically, the alkaline-rich glaze reacts with graphite to form a carbon monoxide gas. Thereafter, dissociation of CO at the interface between SEN and molten metal takes place. This leads to reoxidation of dissolved alloying elements such as REM (Rare Earth Metal). This reoxidation forms the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high-viscous alumina-rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. Furthermore, these uneven areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the previously mentioned SEN´s uneven areas may provide a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxide inclusions on the SEN internal surface and thereafter the clogging. The study revealed the disadvantages of the glass/silicon powder coating applications and the SEN decarburization. The decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials from a commercial Submerged Entry Nozzle (SEN), were also investigated for different gas atmospheres consisting of CO2, O2 and Ar. The gas ratio values were kept the same as it is in a propane combustion flue gas at different Air-Fuel-Ratio (AFR) values for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out under nonisothermal conditions followed by isothermal heating. The decarburization ratio (α) values of all three refractory types were determined by measuring the real time weight losses of the samples. The results showed the higher decarburization ratio (α) values increasing for MgO-C refractory when changing the Air-Fuel combustion to Oxygen-Fuel combustion at the same AFR value. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times compared to heating at lower temperatures during longer holding times for Al2O3-C samples. Diffusion models were proposed for estimation of the decarburization rate of an Al2O3-C refractory in the SEN. Two different methods were studied to prevent the SEN decarburization during preheating: The effect of an ZrSi2 antioxidant and the coexistence of an antioxidant additive and a (4B2O3 ·BaO) glass powder on carbon oxidation for non-isothermal and isothermal heating conditions in a controlled atmosphere. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina-graphite refractory base materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by a (4B2O3 ·BaO) glaze during the green body sintering led to an excellent carbon oxidation resistance. The effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation of the Al2O3-C coated samples were investigated. Trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on the industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface as well as prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.
184

Strukturuntersuchungen an Methan- und Kohlenstoffdioxid-Clathrat-Hydraten / Crystal structure analysis of methane- and carbon doixide clathrate hydrate

Klapproth, Alice 29 October 2002 (has links)
No description available.
185

Psychiatric symptoms in idiopathic rapid-eye-movement sleep behaviour disorder

Tuineag, Maria 05 1900 (has links)
Le trouble comportemental en sommeil paradoxal (TCSP) idiopathique est caractérisé par une activité motrice indésirable et souvent violente au cours du sommeil paradoxal. Le TCSP idiopathique est considéré comme un facteur de risque de certaines maladies neurodégénératives, particulièrement la maladie de Parkinson (MP) et la démence à corps de Lewy (DCL). La dépression et les troubles anxieux sont fréquents dans la MP et la DCL. L’objectif de cette étude est d’évaluer la sévérité des symptômes dépressifs et anxieux dans le TCSP idiopathique. Cinquante-cinq patients avec un TCSP idiopathique sans démence ni maladie neurologique et 63 sujets contrôles ont complété la seconde édition du Beck Depression Inventory (BDI-II) et le Beck Anxiety Inventory (BAI). Nous avons aussi utilisé le BDI for Primary Care (BDI-PC) afin de minimiser la contribution des facteurs confondant dans les symptômes dépressifs. Les patients avec un TCSP idiopathique ont obtenu des scores plus élevés que les sujets contrôles au BDI-II (9.63 ± 6.61 vs. 4.32 ± 4.58; P < 0.001), au BDI-PC (2.20 ± 2.29 vs. 0.98 ± 1.53; P = 0.001) et au BAI (8.37 ± 7.30 vs. 3.92 ± 5.26; P < 0.001). Nous avons également trouvé une proportion plus élevée des sujets ayant des symptômes dépressifs (4/63 ou 6% vs. 12/55 ou 22%; P = 0.03) ou anxieux (9/50 or 18% vs. 21/43 ou 49%; P = 0.003) cliniquement significatifs. La proportion des sujets ayant des symptômes dépressifs cliniquement significatifs ne change pas en utilisant le BDI-PC (11/55 or 20%) Les symptômes dépressifs et anxieux sont fréquents dans le TCSP idiopathique. L’examen de routine des patients avec un TCSP idiopathique devrait inclure un dépistage systématique des symptômes dépressifs et anxieux afin de les prévenir ou les traiter. / Idiopathic rapid-eye-movement sleep behaviour (iRBD) disorder can be a premotor feature of Parkinson’s disease (PD) or dementia with Lewy bodies (DLB). Depressive and anxiety symptoms are frequent nonmotor features in PD or DLB. We assessed the frequency and severity of depressive and anxiety symptoms in patients with iRBD compared to healthy control subjects. Fifty-five iRBD patients and 63 age and sexmatched healthy subjects were studied. Participants completed the Beck Depression Inventory – Second Edition (BDI-II) and Beck Anxiety Inventory (BAI). We assessed the depressive and anxiety symptoms and compared the proportion of participants with clinically significant depressive or anxiety symptoms. We also used the BDI for Primary Care (BDI-PC) to minimize confounding factors that could overestimate depressive symptoms. iRBD patients scored higher than controls on the BDI-II (9.63 ± 6.61 vs. 4.32 ± 4.58; P < 0.001)), BDI-PC (2.20 ± 2.29 vs. 0.98 ± 1.53; P = 0.001) and BAI (8.37 ± 7.30 vs. 3.92 ± 5.26; P < 0.001). Compared to controls, we found a higher proportion of patients with iRBD with either clinically significant depressive (4/63 or 6% vs. 12/55 or 22% P = 0.03) or anxiety symptoms (9/50 or 18% vs. 21/43 or 49%; P = 0.003). The proportion of iRBD patients with clinically significant depressive symptoms remains unchanged using the BDI-PC (11/55 or 20%). Depressive and anxiety symptoms are frequent features in iRBD. Routine examination of patients with iRBD disorder should include an assessment of depressive and anxiety symptoms in order to prevent or treat them.
186

Étude de la perfusion cérébrale régionale dans le trouble comportemental en sommeil paradoxal

Vendette, Mélanie 12 1900 (has links)
Le trouble comportemental en sommeil paradoxal (TCSP) se caractérise par une perte de l’atonie musculaire en sommeil paradoxal et par des manifestations motrices élaborées souvent associées au contenu onirique. Le TCSP peut apparaître sous une forme idiopathique (TCSPi), mais il est fréquemment lié à certains désordres neurodégénératifs, dont les synucléinopathies. Des marqueurs biologiques des synucléinopathies, tels que la présence d’anomalies au plan de la motricité, de la détection des odeurs ainsi que de la discrimination des couleurs, ont été retrouvés dans le TCSPi. De plus, des perturbations de l’activité cérébrale en neuroimagerie ainsi que du fonctionnement cognitif ont été observées chez ces patients. Des études ont démontré que le TCSPi pouvait précéder l’apparition d’une maladie de Parkinson (MP) ou d’une démence à corps de Lewy (DCL). Ceci suggère que le TCSPi représenterait un facteur de risque des synucléinopathies. L’objectif principal du présent projet est d’étudier les anomalies du débit sanguin cérébral régional (DSCr) de repos avec la tomographie par émission monophotonique (TEM) dans le TCSPi. Deux études ont été réalisées. La première visait à comparer le DSCr entre des patients avec un TCSPi et des sujets sains, puis d’explorer la relation entre l’activité cérébrale et la présence de marqueurs biologiques des synucléinopathies. Les résultats ont montré une diminution de la perfusion cérébrale dans les régions frontales et pariétales ainsi qu’une augmentation de la perfusion au niveau du pont, du putamen et des hippocampes chez les patients avec un TCSPi. Une relation significative entre la performance des sujets avec un TCSPi à une épreuve de discrimination des couleurs et la perfusion cérébrale au niveau des régions frontales et occipitales a été mise en évidence. Dans l’ensemble, ces résultats ont démontré des anomalies du DSCr chez les patients avec un TCSPi qui sont similaires à celles observées par d’autres études en neuroimagerie dans la MP. Ceci suggère des atteintes neuroanatomiques semblables entre ces pathologies. La seconde étude en TEM a été effectuée dans le but d’examiner les modifications du DSCr associées aux perturbations du fonctionnement cognitif dans le TCSPi. Pour ce faire, le DSCr a été comparé entre un sous-groupe de patients avec un TCSPi et un trouble cognitif léger (TCL), un sous-groupe de patients avec un TCSPi sans TCL et un groupe de sujets sains. Les résultats ont montré que seuls les patients avec un TCSPi et un TCL présentaient une diminution de la perfusion cérébrale dans les aires corticales postérieures (occipitales et temporo-pariétales). Ces observations sont similaires à celles rapportées dans la MP avec démence et la DCL dans les études en neuroimagerie. En conclusion, les résultats de ces deux études ont montré des perturbations du DSCr dans le TCSPi, similaires à celles observées dans les synucléinopathies. Par ailleurs, nos résultats ont mis en évidence que les patients avec un TCSPi et un TCL présentaient les mêmes anomalies de la perfusion cérébrale que les patients avec une MP avec démence et/ou une DCL. La présence de tels marqueurs des synucléinopathies dans le TCSPi suggère que ces patients pourraient être plus à risque d’évoluer vers ce type de maladie neurodégénérative. / Rapid eye movement sleep behavior disorder (RBD) is a parasomnia characterized by intermittent loss of normal atonia during REM sleep and elaborate motor activity associated with dreams. RBD may occur in an idiopathic form (iRBD), but is frequent in neurodegenerative diseases characterized by alpha-synuclein deposition such as Parkinson’s disease (PD) and dementia with Lewy bodjes (DLB). Biomarkers of synucleinopathies, such as motor, olfaction and color discrimination dysfunctions have been found in patients with iRBD. Moreover, impaired cerebral activities with neuroimaging and cognitive perturbations have also been detected in those patients. Longitudinal studies have demonstrated that iRBD might precede PD or DLB by several years. This suggests that iRBD could represent a risk factor of synucleinopathies. The goal of the present research was to investigate the resting regional cerebral blood flow (rCBF) in an iRBD sample using single photon emission computerized tomography (SPECT) neuroimaging. This led to two different studies. The aim of the first study was to compare the rCBF between a group of patients with iRBD and a group of healthy control subjects, and to explore correlations between rCBF of iRBD patients and markers of synucleinopathies. The results of this study showed that compared to controls, iRBD patients had decreased perfusion in frontal and parietal cortical regions and an increased perfusion in pons, putamen and hippocampus bilaterally. Moreover, a significant correlation between brain perfusion in frontal and occipital cortex and performance on a color discrimination test was found in iRBD patients. The brain perfusion anomalies observed in our iRBD patients are similar to those observed in PD in functional neuroimaging studies, suggesting similar neuroanatomic basis between these two pathologies. The objective of the second study was to investigate brain perfusion changes associated with mild cognitive impairment (MCI) in iRBD. We compared rCBF of a sub-group of patients with iRBD and MCI, a sub-group of patients with iRBD without MCI and a group of healthy control subjects. The results showed that only iRBD with MCI showed decreased perfusion in posterior brain regions, in occipital and temporo-parietal areas. These anomalies found in iRBD with MCI are similar to those reported in other studies in PD patients with dementia (PDD) and DLB in neuroimaging studies. To conclude, the results of this research showed brain perfusion abnormalities in iRBD patients similar to those found in synucleinopathies. One of our studies demonstrated a specific pattern of cerebral anomalies with SPECT, similar to those found in PDD and DLB, in patients with iRBD and MCI compared to iRBD without MCI. These biomarkers of synucleinopathies in iRBD suggest that these patients might be at higher risk to develop a neurodegenerative disease associated with alpha synuclein deposition.
187

The Politics of Friends in Modern Architecture : 1949-1987

Troiani, Igea Santina January 2005 (has links)
This thesis aims to reveal paradigms associated with the operation of Western architectural oligarchies. The research is an examination into "how" dominant architectural institutions and their figureheads are undermined through the subversive collaboration of younger, unrecognised architects. By appropriating theories found in Jacques Derrida's writings in philosophy, the thesis interprets the evolution of post World War II polemical architectural thinking as a series of political friendships. In order to provide evidence, the thesis involves the rewriting of a portion of modern architectural history, 1949-1987. Modern architectural history is rewritten as a series of three friendship partnerships which have been selected because of their subversive reaction to their respective establishments. They are English architects, Alison Smithson and Peter Smithson; South African born architect and planner, Denise Scott Brown and North American architect, Robert Venturi; and Greek architect, Elia Zenghelis and Dutch architect, Rem Koolhaas. Crucial to the undermining of their respective enemies is the friends' collaboration on subversive projects. These projects are built, unbuilt and literary. Warring publicly through the writing of seminal texts is a significant step towards undermining the dominance of their ideological opponents. It also appears that through the making of these projects, the unrecognised architects are able to convert themselves to being recognised as new figureheads. This thesis contends that as a consequence of the power within each of the three friendship partnerships, the architects are enabled to collaborate against the dominant ideology of their respective enemies and gain status. It also contends that a cycle of friendship and warring is the political system by which the institution of modern architecture has historically reengineered itself to suit the times.
188

Právo stavby a jiné možnosti realizace stavby na cizím pozemku / Superficiary right of building and other possibilities of building on land of another

Lupač, Petr January 2016 (has links)
The topic of this thesis is the superficiary right of building (and other possibilities of building on the land belonging to a third party, though the focus is primarily on the institution of the superficiary right of building). The principle "superficies solo cedit" was reintroduced in Czech legislation when the new Civil Code (Act No. 89/2012, Coll.) came into force. Along with this principle, the institution known as superficiary right of building has also returned to Czech law after a hiatus of more than 50 years. This thesis seeks to provide a comprehensive interpretation of the superficiary right of building, to explain the individual rights and obligations arising from the superficiary right of building, and to compare the institution of superficiary right of building to other possibilities of erecting a building on land which belongs to someone else. The first chapter defines some of the basic concepts which facilitate the explanation of individual issues and the understanding of certain connections in the following chapters. The second chapter describes the history of the superficiary right of building, which has its roots in the times of ancient Rome. This chapter also undertakes a characterization of legal regimes which were previously in force on the territory of todayʼs Czech Republic. Over the...
189

Oceňování věcných břemen - komparace různých metod ocenění / Valuation of Easements - Comparison of Valuation Methods

Prokop, Jan January 2019 (has links)
In this diploma thesis I deal with methods of valuation of easements according to current legislation and methodology. The easements, as a tool for limiting or extending the rights to real estate, are dealt with in a general way, I will state the methods for their valuation and subsequently apply these methods to specific easements.
190

Ionizační detektor pro EREM / Ionization Detector for Variable Pressure SEM

Černoch, David January 2009 (has links)
This graduation theises deal with influence of an additional grating possitioned berween the sample and the ionisation detektor of the environmental scannin elektron microscope on signal detection. Signal level is measured for changing pressure, at different voltages on the aditional grating, at different sample - additional electrode distance and at different sample - detektor distance. Influence of the additional grating is simulated for real working conditions on PC.

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