Carbon fiber based composites are an essential material in weight-critical applications such as in the aerospace industry. However, these materials are susceptible to damage such as matrix microcracking and fiber/matrix debonding (diffuse damage), which occurs at stresses much lower than the failure stress. A T700/M21 [0/90]s laminate was tensile loaded to introduce diffuse damage and prepared for a study on the initiation of transverse microcracks. The material was tensile loaded in a [+45/-45]s orientation to induce diffuse damage. A diffuse damage indicator was developed by measuring the decrease in shear stiffness. Samples with diffuse damage levels of 0, 0.05, 0.10, 0.15, 0.20, and 0.25 were prepared to be tensile tested in a [0/90]s orientation to induce microcracks. A successful development of the microcracking test procedure was performed. The edge of the material was studied with optical microscopy and x-ray to establish the structure of the fiber bundle geometry when undamaged. A sample containing microcracks was treated with diiodomethane dye penetrant, which successfully highlighted microcracks during x-ray imaging. The application time was not sufficient to produce consistent x-ray images over time, so a 45 minute soak time was recommended instead. The same damaged sample was subjected to a tomographic scan without a dye penetrant and while unloaded. Transverse microcracks were successfully identified from the data, although the results were not clean enough and likely omitted some smaller microcracks. Results are expected to be cleaner if performed during tensile testing. Future tensile testing will quantify the induced crack density of samples containing various degrees of initial diffuse damage, either using x-rays with a dye penetrant or using x-ray microtomography.

This master thesis is focused on groundwater remediation of chlorinated ethylenes and methanes in the area of chemical factory Spolchemie in the Czech Republic, Ústí nad Labem city. For these purposes nano zero valent iron particles were used. For the remediation two separate applications of different types of particles together in suspension with tracer (lithium chloride), were carried out. The results from the first application were evaluated by the supervisor of this thesis and are briefly summarized and discussed together with the second application which was evaluated by the author of this thesis. Second application of particles was carried out in October 2015 and observed for 424 days. Observation consisted of monitoring of groundwater level, physical-chemical parameters and collection of water samples for the analysis of concentrations of chlorinated hydrocarbons, their degradation products and several chosen ions. Nanoiron particles had the assumed effect onto the physical-chemical parameters and reduction of contamination. The application of tracer had proven the expected groundwater flow and made a possibility to distinguish between the process of reductive dehalogenation and dilution caused by the injected water, the dilution did not exceeded 5 % in most monitored points. Other...

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A new geophysical method was developed to satisfy a need for in-situ density measurements. Various situations, such as a gravity dam wall requires that density measurements should be done without damage to the structure. The sample volume should also not be that large in order to be sensitive enough for variations. This method measures the in-situ density of the weathered layer and other man made structures, using seismic waves in three directions. The seismic waves utilized are P-waves and S-waves. It is however surface waves that are treated like body waves because they do not separate at this shallow depth. These waves are very sensitive to the attenuation factor, which is in turn sensitive to certain physical properties of the propagation medium. This factor is utilsed when the multi layer problem is encountered. The maximum depth of exploration is 2-5m and depends solely on the seismic skin depth. This method utilises a large base plate. The source is a large sledge hammer and shots are done at each side of the base plate. Different dominant frequencies are identified and used to calculate the densities of the layers associated with that specific frequency. The velocities of the subsurface are determined by small seismic refraction surveys. The method will find application mainly in the civil and engineering geology fields. The main application will be to determine subsurface densities and small movement elasticity modulli for engineers to aid in obtaining adequate design parameters. Case studies on three different geologic environments are presented. The results indicate that this method will be useful, although certain modifications are recommended to make this method even faster and more user friendly. / Thesis (PhD)--University of Pretoria, 2007. / Geology / unrestricted

For sites contaminated with chloroethene non-aqueousphase liquids, designing a remediation system that couples in situ chemical oxidation (ISCO) with potassium permanganate (KMnO4) and microbial dechlorination may be complicated because of the potentially adverse effects of ISCO on anaerobic bioremediation processes. Therefore, one-dimensional column studies were conducted to understand the effect of permanganate oxidation on tetrachloroethene (PCE) dechlorination by the anaerobic mixed culture KB-1. Following the confirmation of PCE dechlorination, KMnO4 was applied to all columns at a range of concentrations and application velocities to simulate varied distances from oxidant injection. Immediately following oxidation, reductive dechlorination was inhibited; however, after passing several pore volumes of sterile growth medium through the columns after oxidation, a rebound of PCE dechlorination activity was observed in every inoculated column without the need to reinoculate. The volume of medium required for a rebound of dechlorination activity differed from 1.1 to 8.1 pore volumes (at a groundwater velocity of 4 cm/d), depending on the specific condition of oxidant application.

Transfer hydrogenation has been recognized to be an important synthetic method in both academic and industrial research to obtain valuable products including alcohols. Transition metal catalysts based on precious metals, such as Ru, Rh and Ir, are typically employed for this process. In recent years, iron-based catalysts have attracted considerable attention as a greener and more sustainable alternative since iron is earth abundant, inexpensive and non-toxic. In this work, a combination of iron disulfide with chelating bipyridine ligand was found to be effective for the transfer hydrogenation of a variety of ketones to the corresponding alcohols in the presence of a simple base. It provided a convenient and economical way to conduct transfer hydrogenation. A plausible role of sulfide next to the metal center in facilitating the catalytic reaction is demonstrated.

Load cells are very important components in a robot system. They help the robot to get feedback from the environment around it and generate control signals accordingly. However, like every other sensor, load cells need to be calibrated over time to maintain their accuracy and precision. In the current method, they need to be detached from the robot. Then known weights are hung below the load cells to get the raw signal from the load cells. These two types of values will then be used to generate the equations that convert the raw signal to the force values. This is a challenge as not many robots are maintenance-friendly so detaching the load cells can take a lot of time, not to mention the process can damage the load cells if not conducted carefully. This research project utilizes mechanical simulation to calculate the known force values acting on the load cells without taking them out of the robot system. Then these force values are used for the calibration process. In this thesis, the in situ calibration method will be conducted on the actuator-controlled pendulum, and a bipedal robot when it is hanging on the gantry and standing on the ground. Also, since mechanical simulation requires a lot of computational power, a geometry simplification method will also be introduced so this in situ calibration method can be used for ordinary personal computers. The results show that the new calibration method is easy to work with, the force values still meet the requirements for calibration, and the computer only needs 10-12 seconds to run each simulation. / Master of Science / A robotic system usually need the load cell to generate the correct control signal. However, the load cell needs to be calibrated over time for maintenance. The current calibration method requires the load cell to be detached from the robot so the user can apply known forces to the load cell. This thesis introduces an in situ calibration method that can calculate forces that are applied to the load cell so the user does not need to detach the load cell from the robot. An optimization method is also introduced to make the calibration process can be done on an ordinary personal computer.

Die vorliegende Arbeit beschäftigt sich mit der volumenbildgebenden Untersuchung von mechanischen Ermüdungsprozessen in Titan-Zahnimplantaten. Im Vordergrund steht die Entwicklung einer neuen Messmethode der In-situ-Mikrotomografie am Synchrotron. Zahnimplantate werden beim Gebrauch mechanisch wiederholt belastet (Wechsellast). Nach vielen zyklischen Belastungen können aufgrund von mikroplastische Verformungen Ermüdungsschäden auftreten. Diese können im Extremfall zum Versagen und Verlust eines Implantats führen. Die Computertomographie ist eine sehr geeignete zerstörungsfrei Prüfmethode, um Zahnimplantate zu untersuchen. Diese Arbeit erweitert die bisherige CT-Methode insofern, dass In-situ-Beobachtungen bei mechanischer Belastung möglich sind. Die in dieser Arbeit untersuchten Zahnimplantate weisen an der Implantat-Abutment-Grenzfläche bei eintretender Ermüdung einen Mikrospalt auf. Dieser wird als Indikator für einsetzende Fatigue- Prozesse benutzt. Der in der Synchrotron CT verfügbare Inlinephasenkontrast ermöglicht eine verbesserte Bestimmung der Mikrospaltgröße. Da die schnellen Bewegungen der Ermüdungsprüfung mittels Standard-CT-Verfahren schwer zu erfassen sind, war die stroboskopische Aufnahmemethode das zielführende Messverfahren, um in-situ-Prüfung zu ermöglichen. Die 4 kommerziellen Zahnimplantattypen werden neben der In-situ-Fatigue Prüfung auch mittels klassischer Ermüdungsprüfung untersucht und mit der Neuen Messmethode verglichen. Die hier entwickelte In-situ-Fatigue-Prüfstation kann Proben bis zu 345 N tomographisch untersuchen. Neben den experimentellen Untersuchungen wird eine statische FEM-Betrachtung durchgeführt und mit experimentellen Messdaten verglichen. Zuletzt wird mit der entwickelten Messtation Knochenrisse in der Implantat Umgebung untersucht. / The present work deals with the volume imaging investigation of mechanical fatigue processes in titanium dental implants. The focus is on the development of a new measurement method of in-situ microtomography at the synchrotron. Dental implants are exposed to repeated mechanical loads. After many cyclic loads, fatigue damage can occur due to microplastic deformation. These can lead to failure and loss of an implant. Computed tomography is a very suitable non-destructive testing method to examine dental implants. This work extended the existing method to the point where in situ CT observations under mechanical loading are achievable. The dental implants investigated in this work exhibit a microgap at the implant-abutment interface when fatigue occurs. This is used as an indicator for the occurrence of fatigue processes. The inline phase contrast available in synchrotron CT can be used to determine the size of the microgap. Since the fast motions of fatigue testing are difficult to capture using standard CT techniques, the stroboscopic imaging method was the used measurement technique, to enable in-situ testing. In addition to in-situ fatigue testing, the 4 commercial dental implant types are also examined and compared with each other by means of classical fatigue testing. The developed in-situ fatigue test station can tomographically investigate specimens up to 345 N. In addition to the experimental investigations, a static FEM analysis is performed and compared with experimental measurement data. Finally, the developed measuring station is used to investigate bone cracks in the implant environment.

Today, zeolites play a considerable role in many industrial fields, especially in heterogeneous catalysis. Well-defined microporous structure combined with acidity provides exceptional size and shape selectivity, making zeolites indispensable in petrochemistry. However, the micropores can cause diffusion limitations and, in turn, a drop in reaction rate and selectivity. Hence, the development of modification methodologies on zeolite textural properties is one of the attention-grabbing research topics nowadays. For example, to overcome transport limitations in zeolites, the particle size can be reduced, or a system of larger auxiliary pores can be introduced [1]. One of the most promising methods for introducing secondary pores on a large scale is desilication since it is low-cost, versatile, and easy [2]. Despite its simplicity, the desilication mechanism is still a matter of discussion. In detail, it is not well-understood: 1. The influence of different species on mesopore formation kinetics 2. How aluminum is assembled back into the zeolite 3. Which types of aluminum species form throughout the treatment. The present study tries to answer these questions by relating ex-situ and in-situ NMR. The proposed ex-situ 29Si MAS NMR approach allows monitoring the development of mesoporosity and silicon extraction by analyzing Q3 and Q4 changes. The combination of ex-situ with in-situ 29Si MAS NMR study showed that the limiting step of Si extraction is the transformation of Q3 into Q2. 27Al MAS NMR combined with MQMAS showed the formation of new aluminum species after desilication. It was shown that some of the Al framework T-sites might dissolve during alkaline treatment. In-situ 27Al NMR indicates redistribution of dissolved aluminum upon desilication.