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High SiMo cast iron components in automotive exhaust systems are exposed to high-temperature oxidation over time. Quantitative analysis of formed oxide scale is therefore important for the assessment of a component durability. The brittle nature of multilayered scale and thermal stress limits capture of a true topology using traditional 2D destructive cut and polish methods. In this study, nondestructive high spatial-resolution 3D µCT analysis was performed on 2.90-mm-diameter oxidized specimens which permitted direct observation with 3.5 µm pixel resolution. The specimens were oxidized in three sequential time steps for a total 100 h at 700 °C and 800 °C in air and combustion gas atmospheres. A MATLAB-coded algorithm was used to quantify the topology, thickness variation in internal and external scale layers, and scale/metal interface unevenness. Scale topology was linked to oxidation temperature and gas atmosphere. A water vapor environment increases scale/metal interface unevenness and scale layer thickness irregularity which were related to an accelerated oxidation rate.

Prior to European settlement, swamps, marshes, lakes, and streams were the major landscape features of the Chicago region. Much of this has been altered or lost in the past one-hundred-and-fifty years. We examined the changes in aquatic environments and fauna in Cook County, Illinois, using 1890–1910 and 1997–2017 as our focus intervals. The extents of aquatic features from historical topographic maps were imported into a GIS database and compared with the modern USGS National Hydrography Dataset. Historical and modern spatial data on aquatic animals were collected from museum collection and survey reports. Overall, the total area of wetlands and water bodies has decreased by about a third, while swamps and marshes have been drained or converted into lakes and ponds. Fifty-four of 80 historic molluscan species are not recently recorded, and 26 current species are not recorded in the historical data, including 6 considered to be invasive. Of 54 fish species in the historic data, 23 are no longer present and about 50% of the remaining species have undergone range reductions. Three out of 10 species of reptiles have disappeared. All 25 aquatic birds reported from the 1890–1910 period are still extant and an additional 13 have been reported in recent times, possibly due to increased collection effort. The Chicago region provides a case study of the impact of anthropogenic landscape change on biota. Large scale extirpations of native species have corresponded to a shift to a highly fragmented landscape of small ponds and reduced swamps and marshes.

The quality of spheroidal graphite cast iron (SGI) castings is directly related to the morphology of graphite nodules. Therefore, accurate and comprehensive quantitative evaluation of microstructure is critical for industrial practices. The most influential morphological characteristics of the graphite phase in SGI can be divided into three categories: (1) shape and size of individual graphite nodules, (2) total volume of graphite phase and nodule number, and (3) spatial distribution. During the last decades, SGI structure analysis has progressed from visual observation of polished cross section and quantitative 2D techniques (metallography and automated SEM/EDX) to observation of the real 3D structure using micro-computed tomography (µCT) scanning. In this article, 2D and 3D morphological characteristics of graphite nodules were determined by µCT scanning and compared. 3D µCT provides accurate characterization of the real shape factor and diameter of graphite nodules. It was shown that large and small graphite nodules in inoculated SGI have the different modes of space distribution which could be linked to casting solidification.

For real-time computed tomography (CT), a temporal resolution lower than 30 ms is required, which cannot be delivered by conventional CT architectures with a rotation gantry. Stationary CT architecture can achieve a temporal resolution lower than 30 ms by eliminating the physical rotation of the gantry and by electronically sweeping X-ray beams across the gantry. Stationary CT architecture utilizes two separate arrays, one for distributed X-ray sources and another for detectors. These individual X-ray sources are required to be compact, fast, and individually addressable in order to acquire 200+ projections for successful CT reconstruction and to achieve a temporal resolution lower than 30 ms. A compact X-ray tube that fits these requirements is being developed. The aim of this paper was to design an electrostatic electron focusing lens for the first-generation prototype compact X-ray tube primarily consisting of a carbon nanotube-based electron source and a transmission-type anode by studying the multiple variables that affect the focal spot size (FSS) and by comparing different types of electrostatic lenses with the help of simulations. This multivariable simulation study was conducted using an object-oriented particle-in-cell code, OOPIC PRO. The results of these simulations showed the following: Einzel lens can achieve the required FSS (lower than 1 mm); lens aperture, thickness, and location of the lens can be used as a coarse control over the FSS, whereas the lens potential can be used as a fine control; and the chromatic and spherical aberrations can be reduced if Einzel lens is used.

In this article, we offer a look inside our prototype compact X-ray tube by reporting on our findings when we experimentally studied it. We studied the prototype experimentally to characterize its primary components, i.e., carbon nanotube (CNT)-based cold cathode, electrostatic lens and transmission-type anode, and to validate our previous simulation studies. We characterized the CNT-based cold cathode by studying the relationship between the electron emission current and its control parameter, electron extraction voltage. This relationship, commonly known as the current-voltage characteristic, showed an exponential-like nature that is expected from the Fowler-Nordheim model for field emission. Next, we characterized the electrostatic lens by studying the effects of lens voltage on the focal spot size. Their relationship showed a "V" trend and corroborated that we can control the focal spot size by controlling the lens voltage. We then characterized the transmission-type anode of the prototype by studying its output X-ray energy spectra at different anode voltages. We could control the highest and the mean X-ray energies generated from the transmission-type anode using the anode voltage. For the same anode voltage and aluminum filtration, when we compared the Xray energy spectrum generated from the transmission-type anode with that of the conventional reflection-type anode, we observed that the two energy spectra agreed with each other.

Formation of low density graphite phase during solidification increases the volume of semi-solid cast iron with spheroidal graphite (SGI) and resulted pressure could help eliminate shrinkage micro-porosity in casting. Therefore, micro-porosity in casting can be linked to 3D graphite nodule structure. Two experimental SGI's with different levels of shrinkage micro-porosity in castings were intentionally produced by variation in inoculation parameters which influenced graphite nodule structure. 3D-morphological characteristics of graphite nodules and micro-porosity level were determined by μCT scanning. The obtained statistical data was discussed with respect to graphite nodule solidification mode and casting soundness. The capabilities of μCT scanning in predicting micro-shrinkage in SGI casting were compared to the other traditionally used techniques.

Experiments on FRC formation and translation into the interior of a metal shell or liner have been conducted at AFRL. Flux exclusion, collimated light, and interferometer data on magnetized plasma injection will be presented. These are a pre-requisite for FRC compression by liner implosion, experiment progress on which will also be presented. FRC translation, capture, and compression experiments all use primarily axial ∼ 2 Tesla guide and mirror fields established inside the liner, using ∼ 5 millisecond rise time discharges into an array of pulsed magnet coils surrounding the liner implosion portion of the device. A 12 MA, 4.5 MJ axial discharge drives the liner implosion for compression experiments. The FRC capture experiments use 3 capacitor discharges into a segmented theta coil surrounding the FRC formation region to establish a bias field, accomplish pre-ionization of deuterium gas, and provide the reverse field main theta discharge (∼ 1 Megamp) which forms the FRC. This is aided by two cusp field discharges. The guide and mirror fields enable translation of the FRC and its capture in the liner interior region. Diagnostics include pulsed power (current and voltage), magnetic field, field exclusion, He Ne laser interferometry, imaging and spectroscopy, radiography, and both activation and time-of-flight neutron detection. Design features and operating parameters are guided by 2D-MHD simulations.