Die Untersuchung von III-V-Heterostruktur-Grenzflächen spielt aufgrund des starken Einflusses der Grenzflächen auf die Eigenschaften von Halbleiterbauelementen eine elementare Rolle. Die Transmissionselektronenmikroskopie (TEM) hat sich als eines der geeignetsten Methoden für die Analyse von Grenzflächen erwiesen. Jedoch stellt die Interpretation von zweidimensionalen Projektionen, insbesondere bei dreidimensionalen (3D) Strukturen, eine Herausforderung dar, da die Information über die Tiefe in der Projektion verloren geht. In dieser Arbeit wird diskutiert, dass Grenzflächen als 3D Objekte gesehen werden können, insbesondere bei großen Rauheiten oder chemischen Durchmischungen. Zur Charakterisierung von vergrabenen III-V-Halbleitergrenzflächen wurde eine neue analytische Methode auf Basis der Elektronentomographie entwickelt. Diese Methode wird anhand eines (Al,Ga)As/GaAs-Mehrschichtsystems als Fallstudie vorgestellt. Es wird gezeigt, dass die tomographische Rekonstruktion von Grenzflächen ausgenutzt werden kann, um sogenannte Iso-Konzentrationsflächen zu erhalten, welche die Lage einer festgelegten Konzentration an der Grenzfläche beschreiben. Sie erlauben die Erstellung topographischer Höhenkarten, die die Rauheit von Grenzflächen visualisieren und ermöglichen die Bestimmung wesentlicher Grenzflächenparameter wie die quadratische Rauheit oder die lateralen und vertikalen Korrelationslängen. Zusätzlich wurden Isoflächen an unterschiedlichen Konzentrationsniveaus verwendet, um topographische Karten der Grenzflächenbreite zu erzeugen. Die Stärke der Methodik liegt in der Möglichkeit, alle chemisch-strukturellen Parameter von vergrabenen Grenzflächen mit einer einzelnen Tomographiemessung zu bestimmen. Die Applikation dieser neuen Grenzflächentomographie-Technik wird an unterschiedlichen Halbleitermaterialien für optische Anwendungen demonstriert: An einer (Al,Ga)As/GaAs-Mikrokavität, einem (Al,Ga)N/GaN-Bragg-Reflektor und einem 3D (In,Ga)N/GaN-Nanodraht. / The investigation of III-V heterostructure interfaces plays a key role in developing novel semiconductor devices due to the strong influence of interfaces on device characteristics. Transmission electron microscopy (TEM) has proven to be one of the most suitable tools for an interface analysis. The interpretation of two-dimensional projections can be challenging, especially for three-dimensional (3D) structures, since the depth information is lost in the projection. It is discussed in this thesis that interfaces can be seen as 3D objects, particularly when interfaces are subject to large roughnesses or chemical intermixing. A new analytical method for the comprehensive characterization of buried III-V semiconductor interfaces based on electron tomography was developed. This method is applied to an (Al,Ga)As/GaAs multilayer system as a case study. It is shown that the tomographic reconstruction of a tomography needle of this material can be exploited to obtain so-called iso-concentration surfaces. These surfaces describe the positions of a chosen concentration value at the interfaces. They enable the creation of topographic height maps revealing the roughness of several interfaces. The height maps allow the determination of essential interface parameters as the quadratic mean roughness or the lateral and vertical correlation lengths using the height-height correlation function. In addition, height-difference maps based on isosurfaces corresponding to different concentration levels were used to generate topographic maps of the interface width. The methodology’s main strength is the ability to determine all chemical-structural parameters of buried interfaces with a single measurement. This thesis presents the application of this new interfacial tomography technique on semiconducting materials used for optical application purposes: An (Al,Ga)As/GaAs microcavity, an (Al,Ga)N/GaN Bragg reflector and a complex, 3D (In,Ga)N/GaN multi-shell nanowire.

Top hammer drilling uses a percussive force at the top combined with a rotational energy that transmits through a rod to a drill bit that crushes rock. It is a drilling method that is preliminary used in mining, construction and operations under ground. Fatigue strength plays an important role in the drill rods life span. A top hammer drill rod has a through hole in the center called a flush hole used to flush up the drilling cuttings. The flush hole is a weak spot in the rod. In this preliminary study the purpose was to investigate if, and how, the surface in the flush hole affects the fatigue strength in rock drill rods. Four test methods; Refined inner surface, lathed core, without lubricant and sealed hollow bar. With three samples of each method that affected the surface of the flush hole, were used in the manufacturing of the rods and compared to references. Different tests were applied to measure the quality of the flush hole and of the rods. The material used were fatigue tested under a pulsating pull-pull condition with flushing water. Finally, the fracture surfaces were studied. The fatigue test showed that refined inner surface had supreme fatigue strength, the other methods exhibit approximately 10% more cycles than the references. In conclusion the inner surface affects the fatigue strength. The parameter with the most distinct correlation to the fatigue test was surface roughness. Other parameters that seems to affect were oxidation, hardness and scratches. To obtain statistical certainty more samples are needed.

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<p>An experimental investigation has been carried out in order to investigate the effect of surface initial conditions, concentration, nanoparticles size and deposition pattern on pool boiling and jet impingement boiling of nanofluids. A flat copper surface with initial conditions of Ra = 420 nm, Ra = 80 nm and Ra = 20 nm has been used as the boiling surface. Al₂O₃ and CuO nanoparticles have been used with de-ionized water to prepare the nanofluids. At 0.01 vol. % concentration of Al₂O_3, the rate of heat transfer enhanced by 41% and 34% for the Ra = 80 nm and Ra = 20 nm, respectively. While, in the case of Ra = 420 nm, the rate of heat transfer deteriorated by 49%. At 0.005 vol. % concentration the rate of heat transfer deteriorated for all three surfaces. It is believed that the deterioration was due to the uniformity of the deposition. Using 0.01 vol. % concentration of CuO nanofluids resulted in the same trend, however, the rate of heat transfer is less compared to using Al₂O₃nanofluids. For example, in the case of Ra = 80 nm, the rate of heat transfer was reduced by 14%.</p> <p>The effect of nanoparticles size has been investigated by changing the nanoparticles size from 50 nm to 10 nm. The change in nanoparticles size resulted in a significant deterioration in the rate of heat transfer for all three surfaces. It is believed that the deterioration was due to the deposition uniformity. As the deposition uniformity has been found to be a major factor that affects the rate of heat transfer, new approach was introduced to quantify the effect of the rate of deposition on the pool boiling of nanofluids.</p> <p>An experimental investigation has been carried out in order to investigate using submerged impingement jet on the rate of heat transfer using nanofluids. At of 0.005 vol. % concentration of Al₂O₃, surface with Ra = 80 nm, jet to surface vertical distance of 3 mm and Reynolds number of 101311, the rate of heat transfer deteriorated by 19%.</p> <p>Comparing the pool boiling and jet impingement boiling of nanofluids showed that, in the case of jet impingement boiling, the rate of heat transfer was enhanced compared to the case of pool boiling and the deposition was less. However, jet impingement boiling experiments showed deterioration in the rate of heat transfer by 19% compared with pure water.</p> / Master of Applied Science (MASc)

El objetivo de esta investigación fue comparar in vitro los cambios en la rugosidad superficial de la estructura dentaria, generados por los diferentes agentes blanqueadores que contienen peróxido de hidrógeno (HP). El estudio consideró 50 especímenes obtenidos de dientes de bovino, seccionados en bloques dentales (7mm x 7mm x 7mm) y preparados para realizar una lectura inicial de rugosidad superficial (Ra), utilizando un perfilómetro. Las muestras fueron divididas aleatoriamente en 5 grupos (n= 10) según el agente blanqueador al que fueron expuestos: grupo1: Whiteness HP Maxx al 35%, grupo 2: Opalescence Boost 40% de HP, grupo 3: Opalescence Go 10% de HP, el grupo 4: Whiteness Perfect al 10% de peróxido de carbamida (CP) como control positivo y, el grupo 5: control negativo, con suero fisiológico. Al finalizar la etapa del blanqueamiento, las muestras se mantuvieron en suero fisiológico; finalmente, fueron sometidas al perfilómetro para determinar los parámetros de rugosidad superficial post blanqueamiento. Para el análisis estadístico se utilizó el paquete estadístico SPSS® 27.0. Para identificar si los datos siguen una distribución normal, se utilizó la prueba Shapiro Wilk (p > 0.05), luego se aplicó la prueba no paramétrica Prueba de Wilcoxon para muestras relacionadas (Inicial – final). Se concluyó que al aplicar los diferentes agentes blanqueadores que contienen peróxido de hidrogeno no se encontraron diferencias estadísticamente significativas entre los grupos; sin embargo, todos los grupos experimentales presentaron diferencias antes y después de la aplicación de los agentes blanqueadores. / The objective of this research was to compare in vitro the changes in the surface roughness of the tooth structure, generated by different bleaching agents containing hydrogen peroxide (HP). The study detected 50 specimens obtained from bovine teeth, sectioned into dental blocks (7 mm x 7 mm x 7 mm) and prepared to perform an initial reading of surface roughness (Ra), using a profilometer. The samples were randomly divided into 5 groups (n= 10) according to the whitening agent to which they were exposed: group 1: Whiteness HP Maxx 35%, group 2: Opalescent Boost 40% HP, group 3: Opalescent Go 10% HP, group 4: Whiteness Perfect with 10% carbamide peroxide (CP) as positive control and group 5: negative control, with physiological saline. At the end of the bleaching stage, the samples were kept in physiological saline solution; Finally, some profilometric measurements were performed to determine the postbleaching surface roughness parameters. The SPSS® 27.0 statistical package was used for statistical analysis. To identify whether the data follow a normal distribution, the Shapiro Wilk test was used (p > 0.05), then the non-parametric Wilcoxon test was applied for related samples (Initial – final). It is concluded that when applying the different whitening agents containing hydrogen peroxide, no statistically significant differences were found between the groups; however, all experimental groups presented differences before and after the application of the whitening agents.

Yes / The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group (RNG) k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-ε model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning's roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases. / National Natural Science Foundation of China (Grants No. 11361002 and 91230111), the Natural Science Foundation of Ningxia, China (Grant No. NZ13086), the Project of Beifang University of Nationalities, China (Grant No. 2012XZK05), the Foreign Expert Project of Beifang University of Nationalities, China, and the Visiting Scholar Foundation of State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, China (Grant No. 2013A011).

No / This study aimed at examining the biophysical characteristics of human derived keratinocytes (HaCaT) cultured on cholesteryl ester liquid crystals (CELC). CELC was previously shown to improve sensitivity in sensing cell contractions. Characteristics of the cell integrin expressions and presence of extracellular matrix (ECM) proteins on the liquid crystals were interrogated using various immunocytochemical techniques. The investigation was followed by characterization of the chemical properties of the liquid crystals (LC) after immersion in cell culture media using Fourier transform infrared spectroscopy (FTIR). The surface morphology of cells adhered to the LC was studied using atomic force microscopy (AFM). Consistent with the expressions of the integrins α2, α3 and β1, extracellular matrix proteins (laminin, collagen type IV and fibronectin) were found secreted by the HaCaT onto CELC and these proteins were also secreted by cells cultured on the glass substrates. FTIR analysis of the LC revealed the existence of spectrum assigned to cholesterol and ester moieties that are essential compounds for the metabolizing activities of keratinocytes. The immunostainings indicated that cell adhesion on the LC is mediated by self-secreted ECM proteins. As revealed by the AFM imaging, the constraint in cell membrane spread on the LC leads to the increase in cell surface roughness and thickness of cell membrane. The biophysical expressions of cells on biocompatible CELC suggested that CELC could be a new class of biological relevant material.