Coding Strategies for X-ray Tomography

This work focuses on the construction and application of coded apertures to compressive X-ray tomography. Coded apertures can be made in a number of ways, each method having an impact on system background and signal contrast. Methods of constructing coded apertures for structuring X-ray illumination and scatter are compared and analyzed. Apertures can create structured X-ray bundles that investigate specific sets of object voxels. The tailored bundles of rays form a code (or pattern) and are later estimated through computational inversion. Structured illumination can be used to subsample object voxels and make inversion feasible for low dose computed tomography (CT) systems, or it can be used to reduce background in limited angle CT systems.

On the detection side, coded apertures modulate X-ray scatter signals to determine the position and radiance of scatter points. By forming object dependent projections in measurement space, coded apertures multiplex modulated scatter signals onto a detector. The multiplexed signals can be inverted with knowledge of the code pattern and system geometry. This work shows two systems capable of determining object position and type in a 2D plane, by illuminating objects with an X-ray `fan beam,' using coded apertures and compressive measurements. Scatter tomography can help identify materials in security and medicine that may be ambiguous with transmission tomography alone.

Coarse-silt-fraction mineralogy at DSDP Legs 56 and 57 Holes

Soviet sedimentologists use the term "coarse silt" to denote the size fraction 0.1 to 0.05 mm (50-100 µm). Petelin (1961) has shown that this fraction is most diagnostic for terrigeneous and volcanogenic mineral assemblages and provinces in Recent deep-sea sediments, because of its greatest variability of both heavy and light non-opaque minerals, which may be easily identified by the common immersion method. We believe that the fraction is suitable for mineralogical study of unconsolidated and friable sediments from DSDP cores as well, if the objective is to investigate their source area and transporation tracks. In the case of fine-grained oceanic sediments, mineral composition of the coarse silt does not differ markedly from that of the "coarse fraction" (>62 µm).

The CCRUSH Study: Coarse and fine particulate matter measurements in northeastern Colorado 2009-2012

Coarse (PM10-2.5) and fine (PM2.5) particulate matter in the atmosphere adversely affect human health and influence climate. While PM2.5 is relatively well studied, less is known about the sources and fate of PM10-2.5. The Colorado Coarse Rural-Urban Sources and Health (CCRUSH) study measured PM10-2.5 and PM2.5 mass concentrations, as well as the fraction of semi-volatile material (SVM) in each size regime (SVM2.5, SVM10-2.5), for three years in Denver and comparatively rural Greeley, Colorado. Agricultural operations east of Greeley appear to have contributed to the peak PM10-2.5 concentrations there, but concentrations were generally lower in Greeley than in Denver. Traffic-influenced sites in Denver had PM10-2.5 concentrations that averaged from 14.6 to 19.7 µg/m**3 and mean PM10-2.5/PM10 ratios of 0.56 to 0.70, higher than at residential sites in Denver or Greeley. PM10-2.5 concentrations were more temporally variable than PM2.5 concentrations. Concentrations of the two pollutants were not correlated. Spatial correlations of daily averaged PM10-2.5 concentrations ranged from 0.59 to 0.62 for pairs of sites in Denver and from 0.47 to 0.70 between Denver and Greeley. Compared to PM10-2.5, concentrations of PM2.5 were more correlated across sites within Denver and less correlated between Denver and Greeley. PM10-2.5 concentrations were highest during the summer and early fall, while PM2.5 and SVM2.5 concentrations peaked in winter during periodic multi-day inversions. SVM10-2.5 concentrations were low at all sites. Diurnal peaks in PM10-2.5 and PM2.5 concentrations corresponded to morning and afternoon peaks of traffic activity, and were enhanced by boundary layer dynamics. SVM2.5 concentrations peaked around noon on both weekdays and weekends. PM10-2.5 concentrations at sites located near highways generally increased with wind speeds above about 3 m/s. Little wind speed dependence was observed for the residential sites in Denver and Greeley.

Bulk sediment parameters and coarse-fraction analysis of ODP Leg 178 holes

The area west of the Antarctic Peninsula is a key region for studying and understanding the history of glaciation in the southern high latitudes during the Neogene with respect to variations of the western Antarctic continental ice sheet, variable sea-ice cover, induced eustatic sea level change, as well as consequences for the global climatic system (Barker, Camerlenghi, Acton, et al., 1999). Sites 1095, 1096, and 1101 were drilled on sediment drifts forming the continental rise to examine the nature and composition of sediments deposited under the influence of the Antarctic Peninsula ice sheet, which has repeatedly advanced to the shelf edge and subsequently released glacially eroded material on the continental shelf and slope (Barker et al., 1999). Mass gravity processes on the slope are responsible for downslope sediment transport by turbidity currents within a channel system between the drifts. Furthermore, bottom currents redistribute the sediments, which leads to final build up of drift bodies (Rebesco et al., 1998). The high-resolution sedimentary sequences on the continental rise can be used to document the variability of continental glaciation and, therefore, allow us to assess the main factors that control the sediment transport and the depositional processes during glaciation periods and their relationship to glacio-eustatic sea level changes. Site 1095 lies in 3840 m of water in a distal position on the northwestern lower flank of Drift 7, whereas Site 1096 lies in 3152 m of water in a more proximal position within Drift 7. Site 1101 is located at 3509 m water depth on the northwestern flank of Drift 4. All three sites have high sedimentation rates. The oldest sediments were recovered at Site 1095 (late Miocene; 9.7 Ma), whereas sediments of Pliocene age were recovered at Site 1096 (4.7 Ma) and at Site 1101 (3.5 Ma). The purpose of this work is to provide a data set of bulk sediment parameters such as CaCO3, total organic carbon (TOC), and coarse-fraction mass percentage (>63 µm) measured on the sediments collected from the continental rise of the western Antarctic Peninsula (Holes 1095A, 1095B, 1096A, 1096B, 1096C, and 1101A). This information can be used to understand the complex depositional processes and their implication for variations in the climatic system of the western Pacific Antarctic margin since 9.7 Ma (late Miocene). Coarse-fraction particles (125-500 µm) from the late Pliocene and Pleistocene (4.0 Ma to recent) sediments recovered from Hole 1095A were microscopically analyzed to gather more detailed information about their variability and composition through time. These data can yield information about changes in potential source regions of the glacially eroded material that has been transported during repeated periods of ice-sheet movements on the shelf.

Distribution of coarse and fine sediment fractions at Site 178-1095

Fine-fraction (<63 µm) grain-size analyses of 530 samples from Holes 1095A, 1095B, and 1095D allow assessment of the downhole grain-size distribution at Drift 7. A variety of data processing methods, statistical treatment, and display techniques were used to describe this data set. The downhole fine-fraction grain-size distribution documents significant variations in the average grain-size composition and its cyclic pattern, revealed in five prominent intervals: (1) between 0 and 40 meters composite depth (mcd) (0 and 1.3 Ma), (2) between 40 and 80 mcd (1.3 and 2.4 Ma), (3) between 80 and 220 mcd (2.4 and 6 Ma), (4) between 220 and 360 mcd, and (5) below 360 mcd (prior to 8.1 Ma). In an approach designed to characterize depositional processes at Drift 7, we used statistical parameters determined by the method of moments for the sortable silt fraction to distinguish groups in the grainsize data set. We found three distinct grain-size populations and used these for a tentative environmental interpretation. Population 1 is related to a process in which glacially eroded shelf material was redeposited by turbidites with an ice-rafted debris influence. Population 2 is composed of interglacial turbidites. Population 3 is connected to depositional sequence tops linked to bioturbated sections that, in turn, are influenced by contourite currents and pelagic background sedimentation.

Variable 360° Vector-Sum Phase Shifter With Coarse and Fine Vector Scaling

A CMOS vector-sum phase shifter covering the full 360° range is presented in this paper. Broadband operational transconductance amplifiers with variable transconductance provide coarse scaling of the quadrature vector amplitudes. Fine scaling of the amplitudes is accomplished using a passive resistive network. Expressions are derived to predict the maximum bit resolution of the phase shifter from the scaling factor of the coarse and fine vector-scaling stages. The phase shifter was designed and fabricated using the standard 130-nm CMOS process and was tested on-wafer over the frequency range of 4.9–5.9 GHz. The phase shifter delivers root mean square (rms) phase and amplitude errors of 1.25° and 0.7 dB, respectively, at the midband frequency of 5.4 GHz. The input and output return losses are both below 17 dB over the band, and the insertion loss is better than 4 dB over the band. The circuit uses an area of 0.303 mm2 excluding bonding pads and draws 28 mW from a 1.2 V supply.

Coding Manuals

The VRAG-R is designed to assess the likelihood of violent or sexual reoffending among male offenders. The data set comprises demographic, criminal history, psychological assessment, and psychiatric information about the offenders gathered from institutional files together with post-release recidivism information. The VRAG-R is a twelve-item actuarial instrument and the scores on these items form part of the data set. Because one of the goals of the VRAG-R development project was to compare the VRAG-R to the VRAG, subjects' VRAG scores are included in this data set. Access to the VRAG-R dataset is restricted. Contact Data Services, Queen's University Library (academic.services@queensu.ca) for access.