25 research outputs found
Low-Temperature Heat Capacity of CsPbI<sub>3</sub>, Cs<sub>4</sub>PbI<sub>6</sub>, and Cs<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>
No full textThe heat capacities of CsPbI3, Cs4PbI6, and Cs3Bi2I9 were studied using low-temperature thermal relaxation calorimetry in the temperature range of 1.9-300 K. The three compounds are insulators, with no electronic contribution to the heat capacity. None of them show detectable anomalies in the studied temperature window. Thermodynamic properties at standard conditions are derived. Previously reported results on Cs3Bi2I9 are not fully consistent with the present findings. Moreover, the magnetic susceptibilities of the three title compounds were measured.RST/Reactor Physics and Nuclear MaterialsRST/Fundamental Aspects of Materials and Energ
Kosteberekening in die Duitse literatuur sedert Schmalenbach 1922 : 'n literatuurstudie
No full textDCom, North-West University, Potchefstroom CampusThe author of this study found it necessary to
make an investigation into cost accounting treated
in German literature. This thesis, therefore,
is essentially a study of this literature. Use
was made of German text books in which an exposition
of German cost accounting is given.
Also, in addition to such text books German cost
accounting magazines were consulted. Information
thus obtained has been elucidated , supplemented
and explained with the help of Dutch and English American
works.Doctora
Magnetic relaxation phenomena in the chiral magnet Fe1−xCoxSi: An ac susceptibility study
No full textWe present a systematic study of the ac susceptibility of the chiral magnet Fe1−xCoxSi with x=0.30 covering four orders of magnitude in frequencies from 0.1 Hz to 1 kHz, with particular emphasis to the pronounced history dependence. Characteristic relaxation times ranging from a few milliseconds to tens of seconds are observed around the skyrmion lattice A phase, the helical-to-conical transition and in a region above TC. The distribution of relaxation frequencies around the A phase is broad, asymmetric, and originates from multiple coexisting relaxation processes. The pronounced dependence of the magnetic phase diagram on the magnetic history and cooling rates as well as the asymmetric frequency dependence and slow dynamics suggest more complicated physical phenomena in Fe0.7Co0.3Si than in other chiral magnets
Betrouwbaarheid van jetgroutlagen
No full textIn dit afstudeerverslag wordt een onderzoek naar de risico's en de faalkansen van jetgroutlagen uiteengezet. Eerst worden de voordelen van een jetgroutlaag ten opzichte van andere waterremmende lagen opgesomd waarna de verschillende soorten jetgroutlagen worden besproken. Na het onderzoeken van de optredende onnauwkeurigheden en afwijkingenis een risico-analyse model voor jetgroutlagen voor 2 rastertypen opgesteld. Om indicatiewaarden van veilige ontwerparameters te krijgen is vervolgens de relatie tussen enkele parameters onderzocht aan de hand waarvan een aantal simulaties voor jetgroutlagen is gedaan. De resultaten hiervan zijn in Hoofdtuk 4 en in de bijlagen terug te vinden. Jetgrouting is een techniek waarbij onder hoge druk grond los wordt gesneden en grotendeels vervangen door een water/cement-mengsel. Door dit proces trekkend en roterend tegelijk uit te voeren worden ronde groutkolommen verkregen. Door dit volgens een van te voren bepaald stramien uit te voeren wordt als het ware een ondergrondse vloer gerealiseerd, een zogenaamde jetgroutlaag. Jetgroutlagen kunnen worden toegepast bij de aanleg van verdiepte constructies. Het doel van een jetgroutlaag is te zorgen dat tijdens en na bemaling en afgraving van een bouwput geen grondwater zal toetreden. Tevens kan de jetgroutlaag dienen als stempeling na afgraving van de kuip.Hydraulic EngineeringCivil Engineering and Geoscience
Modeling and Laboratory Study of Carbonated Water Flooding
No full textCarbonated Water Flooding (CWF) is an enhanced oil recovery (EOR) method where an oil reservoir is flooded with water containing dissolved CO2. It is being considered as a promising EOR (Enhanced Oil Recovery) method for maturing light and heavy oil fields. A numerical and experimental study of the CWF was conducted, focusing on the underlying physical phenomena. In MATLAB, a numerical model describing a 1D CWF process was formulated assuming immiscible conditions. Modeling predictions have shown that in this simulator the oil swelling accounts for an increased oil production, together with a reduced residual oil saturation. This reduced residual oil saturation is the consequence of a reduced interfacial tension. However, the effect of this reduced residual oil saturation should be studied thoroughly. In addition to the numerical model, core-flood experiments have been performed using Bentheimer sandstone and n-hexadecane to validate the model predictions. It was found that injecting water containing 3.7% CO2 of the total mass of the aqueous phase reduces the residual oil saturation from pure water flooding to about 12.8. The experiment is performed with periods of injection and no injection, where an experiment with continuous injection would have provided more information about oil banking. The results of the experiment have been used to validate the model. From this validation it is deducted that either the residual oil saturation is reduced if the CO2 content in the oil phase is increased or there are errors in both the experiments and simulations. The mechanisms occurring during CWF are described (oil swelling, viscosity reduction, changing densities, solubility, changes in residual oil saturation).Petroleum EngineeringCivil Engineering and Geoscience
Effects of Alzheimer’s disease and formalin fixation on the different mineralised-iron forms in the human brain
No full textIron accumulation in the brain is a phenomenon common to many neurodegenerative diseases, perhaps most notably Alzheimer’s disease (AD). We present here magnetic analyses of post-mortem brain tissue of patients who had severe Alzheimer’s disease, and compare the results with those from healthy controls. Isothermal remanent magnetization experiments were performed to assess the extent to which different magnetic carriers are affected by AD pathology and formalin fixation. While Alzheimer’s brain material did not show higher levels of magnetite/maghemite nanoparticles than corresponding controls, the ferrihydrite mineral, known to be found within the core of ferritin proteins and hemosiderin aggregates, almost doubled in concentration in patients with Alzheimer’s pathology, strengthening the conclusions of our previous studies. As part of this study, we also investigated the effects of sample preparation, by performing experiments on frozen tissue as well as tissue which had been fixed in formalin for a period of 5 months. Our results showed that the two different preparations did not critically affect the concentration of magnetic carriers in brain tissue, as observable by SQUID magnetometry.RST/Fundamental Aspects of Materials and EnergyOld - Interfaculty Reactor Institut
The influence of dynamic flow behaviour on T-foils
No full textThis research thesis focuses on conducting experimental research into the hydrodynamic properties of a NACA 0012 T-foil in dynamic conditions. An aerodynamically smooth surface was created and used for all dynamic experiments. For exploratory research into the effect of surface finish on the performance of a T-foil in steady state conditions, a second, unfinished but structurally equal, T-foil was made using .15 mm 3D printing layers aligned with the flow.The hydrodynamic properties were determined by conducting experiments in steady state conditions using conventional towing tank methods. Combining all steady state experiments, the lift and drag coefficient on the foil are expressed as a function of angle of attack, freestream velocity and submergence for a Reynolds number of 1.5·105. The surface finish of the second, raw printed, T-foil resulted in a lower critical Reynolds number of 3.3 · 105 compared to 4.5 · 105 for the aerodynamically smooth foil.Dynamic flow conditions were simulated in experiments where the setup was subjected to either: sinusoidal pitch motion, sinusoidal heaving motion or waves. As a result of the imposed motions, the static forces on the setup change and inertial forces occur. To compensate for this, a function was made from all static measurements. The inertial forces are compensated by applying a mass/inertia matrix.Using this new method of towing tank research, the steady state behaviour of a T-foil is described using dynamic experiments. The novel method to determine steady state characteristics includes two angle sweeps, one positive and one negative. The rate of change proves to be sufficiently slow at 0.8 ◦ s−1 for v∞ = 2 ms−1, producing more accurate results while towing tank time can be reduced by 78%.From the steady state results a model is created. Because this model is limited to Re = 1.5 · 105, it is enriched with a prediction model based on X-foil which is compensated for induced drag, finite foil shape and free surface effects.The prediction shows good correlation with the results in z-direction for both imposed sinusoidal heaving and pitching motions. During sinusoidal heaving, flow remains attached longer leading to higher and more stable lift and drag at higher absolute angles. In pitching a similar effect can be seen leading to increased fluctuations and slightly higher average lift compared to the prediction models. For both imposed motions, lower drag is measured with respect to both the predictions and the measurement in steady state conditions. An additional component to the drag occurs during a sinusoidal pitching motion. This additional component has a sinusoidal behaviour equal to the imposed motion which suggests that it is caused by induced drag.When the freestream velocity was increased from 2 to 6 ms−1 in similar waves, it was found that the sinusoidal response of the hydrodynamic forces shifted by ± π rad. Similar to the imposed dynamic motions, predictions show larger values for drag. It was found that the wave height can be related to the drag. When wave height is increased, the drag is reduced.Marine Technolog
Phase diagram and magnetic relaxation phenomena in Cu2OSeO3
No full textWe present an investigation of the magnetic-field-temperature phase diagram of Cu2OSeO3 based on dc magnetization and ac susceptibility measurements covering a broad frequency range of four orders of magnitude, from very low frequencies reaching 0.1 Hz up to 1 kHz. The experiments were performed in the vicinity of Tc=58.2 K and around the skyrmion lattice A phase. At the borders between the different phases the characteristic relaxation times reach several milliseconds and the relaxation is nonexponential. Consequently the borders between the different phases depend on the specific criteria and frequency used and an unambiguous determination is not possible.</p
CENETON: Data Toneel, lijst van Nederlandse toneelstukken tot 1803
No full textThe CENETON database includes detailed descriptions of all Dutch manuscripts and editions of Dutch plays, published until 1803. The database also contains translated works and plays written in foreign languages. Bibliographical data on Dutch plays are included comprising the full title of a play, original author, place of publishing, genre and a list of used persons. The signatures of (public) libraries are included to make it possible to locate a play
