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Description: Washability analysis is the basis for nearly all coal preparation plant separations. Unfortunately, there are no on-line techniques for determining this most fundamental of all coal cleaning information. In light of recent successes at the University of Utah, it now appears possible to determine coal washability on-line through the use of x-ray computed tomography (CT) analysis. The successful development of such a device is critical to the establishment of process control and automated coal blending systems. In this regard, Virginia Tech, Terra Tek Inc., and several eastern coal companies have joined with the University of Utah and agreed to undertake the development of a x-ray CT-based on-line coal washability analyzer with financial assistance from DOE. The three-year project will cost $594,571, of which 33% ($194,575) will be cost-shared by the participants. The project involves development of appropriate software and extensive testing/evaluation of well-characterized coal samples from operating coal preparation plants. Each project participant brings special expertise to the project which is expected to create a new dimension in coal cleaning technology. Finally, it should be noted that the analyzer may prove to be a universal analyzer capable of providing not only washability analysis, but also particle size distribution analysis, ash analysis and perhaps pyritic sulfur analysis.
Date: March 31, 1998
Partner: UNT Libraries Government Documents Department

High definition ultrasound imaging for battlefield medical applications

Description: A team has developed an improved resolution ultrasound system for low cost diagnostics. This paper describes the development of an ultrasound based imaging system capable of generating 3D images showing surface and subsurface tissue and bone structures. We include results of a comparative study between images obtained from X-Ray Computed Tomography (CT) and ultrasound. We found that the quality of ultrasound images compares favorably with those from CT. Volumetric and surface data extracted from these images were within 7% of the range between ultrasound and CT scans. We also include images of porcine abdominal scans from two different sets of animal trials.
Date: June 23, 1996
Creator: Kwok, K.S.; Morimoto, A.K.; Kozlowski, D.M.; Krumm, J.C.; Dickey, F.M.; Rogers, B et al.
Partner: UNT Libraries Government Documents Department

Permeability of laboratory-formed methane-hydrate-bearing sand: Measurements and observations using x-ray computed tomography

Description: Methane hydrate was formed in two moist sands and a sand/silt mixture under a confining stress in an X-ray-transparent pressure vessel. Three initial water saturations were used to form three different methane-hydrate saturations in each medium. X-ray computed tomography (CT) was used to observe location-specific density changes caused by hydrate formation and flowing water. Gas-permeability measurements in each test for the dry, moist, frozen, and hydrate-bearing states are presented. As expected, the effective permeabilities (intrinsic permeability of the medium multiplied by the relative permeability) of the moist sands decreased with increasing moisture content. In a series of tests on a single sample, the effective permeability typically decreased as the pore space became more filled, in the order of dry, moist, frozen, and hydrate-bearing. In each test, water was flowed through the hydrate-bearing medium and we observed the location-specific changes in water saturation using CT scanning. We compared our data to a number of models, and our relative permeability data compare most favorably with models in which hydrate occupies the pore bodies rather than the pore throats. Inverse modeling (using the data collected from the tests) will be performed to extend the relative permeability measurements.
Date: September 15, 2010
Creator: Kneafsey, T. J.; Seol, Y.; Gupta, A. & Tomutsa, L.
Partner: UNT Libraries Government Documents Department

Use of computed X-ray tomographic data for analyzing the thermodynamics of a dissociating porous sand/hydrate mixture

Description: X-ray computed tomography (CT) is a method that has been used extensively in laboratory experiments for measuring rock properties and fluid transport behavior. More recently, CT scanning has been applied successfully to detect the presence and study the behavior of naturally occurring hydrates. In this study, we used a modified medical CT scanner to image and analyze the progression of a dissociation front in a synthetic methane hydrate/sand mixture. The sample was initially scanned under conditions at which the hydrate is stable (atmospheric pressure and liquid nitrogen temperature, 77 K). The end of the sample holder was then exposed to the ambient air, and the core was continuously scanned as dissociation occurred in response to the rising temperature. CT imaging captured the advancing dissociation front clearly and accurately. The evolved gas volume was monitored as a function of time. Measured by CT, the advancing hydrate dissociation front was modeled as a thermal conduction problem explicitly incorporating the enthalpy of dissociation, using the Stefan moving-boundary-value approach. The assumptions needed to perform the analysis consisted of temperatures at the model boundaries. The estimated value for thermal conductivity of 2.6 W/m K for the remaining water ice/sand mixture is higher than expected based on conduction alone; this high value may represent a lumped parameter that incorporates the processes of heat conduction, methane gas convection, and any kinetic effects that occur during dissociation. The technique presented here has broad implications for future laboratory and field testing that incorporates geophysical techniques to monitor gas hydrate dissociation.
Date: February 2002
Creator: Freifeld, Barry M.; Kneafsey, Timothy J.; Tomutsa, Liviu; Stern, Laura A. & Kirby, Stephen H.
Partner: UNT Libraries Government Documents Department

Fan to parallel beam conversion in CAT by rubber sheet transformation

Description: A technique for converting fan-beam projections to parallel-beam projections for use in computed tomography is presented. The problem is approached by use of a rubber sheet transformation. Since the data is discretized, an interpolation step is necessary. For densely sampled data this approach appears satisfactory and a significant reduction in photon noise is observable in computer simulations.
Date: January 1, 1979
Creator: Wecksung, G.W.; Kruger, R.P. & Morris, R.A.
Partner: UNT Libraries Government Documents Department

Methane Hydrate Dissociation by Depressurization in a Mount Elbert Sandstone Sample: Experimental Observations and Numerical Simulations

Description: A preserved sample of hydrate-bearing sandstone from the Mount Elbert Test Well was dissociated by depressurization while monitoring the internal temperature of the sample in two locations and the density changes at high spatial resolution using x-ray CT scanning. The sample contained two distinct regions having different porosity and grain size distributions. The hydrate dissociation occurred initially throughout the sample as a result of depressing the pressure below the stability pressure. This initial stage reduced the temperature to the equilibrium point, which was maintained above the ice point. After that, dissociation occurred from the outside in as a result of heat transfer from the controlled temperature bath surrounding the pressure vessel. Numerical modeling of the test using TOUGH+HYDRATE yielded a gas production curve that closely matches the experimentally measured curve.
Date: January 15, 2011
Creator: Kneafsey, T. & Moridis, G.J.
Partner: UNT Libraries Government Documents Department

Methane hydrate distribution from prolonged and repeated formation in natural and compacted sand samples: X-ray CT observations

Description: To study physical properties of methane gas hydrate-bearing sediments, it is necessary to synthesize laboratory samples due to the limited availability of cores from natural deposits. X-ray computed tomography (CT) and other observations have shown gas hydrate to occur in a number of morphologies over a variety of sediment types. To aid in understanding formation and growth patterns of hydrate in sediments, methane hydrate was repeatedly formed in laboratory-packed sand samples and in a natural sediment core from the Mount Elbert Stratigraphic Test Well. CT scanning was performed during hydrate formation and decomposition steps, and periodically while the hydrate samples remained under stable conditions for up to 60 days. The investigation revealed the impact of water saturation on location and morphology of hydrate in both laboratory and natural sediments during repeated hydrate formations. Significant redistribution of hydrate and water in the samples was observed over both the short and long term.
Date: July 1, 2010
Creator: Rees, E.V.L.; Kneafsey, T.J. & Seol, Y.
Partner: UNT Libraries Government Documents Department

Detective quantum efficiency of CT reconstruction: the detection of small objects

Description: The loss of detection sensitivity incurred by any stage of image processing may normally be characterized by the frequency dependence of the detective quantum efficiency (DQE) of that stage of processing, provided the image is represented in continuous coordinates. However, limitations to the DQE concept arise when discretely sampled projection data are used to obtain discretely sampled computed tomographic (CT) reconstructions. The source of these limitations is the aliasing produced by the discrete sampling which mixes contributions from various frequencies. An associated problem is that the signal-to-noise ratio (SNR) for the detection of an object can depend upon the position of the object relative to the discrete reconstruction pixels. The effective SNR for discrete images must take into account this variation. While there may be no loss in the detection SNR for reconstructions in continuous coordinates (DQE = 100%), a reduction in the SNR will result from aliasing for discrete reconstructions. A simple one-dimensional model elucidates the characteristics of discrete CT reconstruction.
Date: January 1, 1979
Creator: Hanson, K.M.
Partner: UNT Libraries Government Documents Department

Examination of Hydrate Formation Methods: Trying to Create Representative Samples

Description: Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, ...
Date: April 1, 2011
Creator: Kneafsey, T.J.; Rees, E.V.L.; Nakagawa, S. & Kwon, T.-H.
Partner: UNT Libraries Government Documents Department

Characterization of porosity in support of mechanical property analysis

Description: Previous laboratory investigations of tuff have shown that porosity has a dominant, general effect on mechanical properties. As a result, it is very important for the interpretation of mechanical property data that porosity is measured on each sample tested. Porosity alone, however, does not address all of the issues important to mechanical behavior. Variability in size and distribution of pore space produces significantly different mechanical properties. A nondestructive technique for characterizing the internal structure of the sample prior to testing is being developed and the results are being analyzed. The information obtained from this technique can help in both qualitative and quantitative interpretation of test results.
Date: December 31, 1992
Creator: Price, R.H.; Martin, R.J. III & Boyd, P.J.
Partner: UNT Libraries Government Documents Department


Description: The Stanford University Petroleum Research Institute (SUPRI-A) studies oil recovery mechanisms relevant to thermal and heavy-oil production. The scope of work is relevant across near-, mid-, and long-term time frames. In August of 2000 we received funding from the U. S. DOE under Award No. DE-FC26-00BC15311 that completed December 1, 2003. The project was cost shared with industry. Heavy oil (10 to 20{sup o} API) is an underutilized energy resource of tremendous potential. Heavy oils are much more viscous than conventional oils. As a result, they are difficult to produce with conventional recovery methods. Heating reduces oil viscosity dramatically. Hence, thermal recovery is especially important because adding heat, usually via steam injection generally improves displacement efficiency. The objectives of this work were to improve our understanding of the production mechanisms of heavy oil under both primary and enhanced modes of operation. The research described spanned a spectrum of topics related to heavy and thermal oil recovery and is categorized into: (1) multiphase flow and rock properties, (2) hot fluid injection, (3) improved primary heavy-oil recovery, (4) in-situ combustion, and (5) reservoir definition. Technology transfer efforts and industrial outreach were also important to project effort. The research tools and techniques used were quite varied. In the area of experiments, we developed a novel apparatus that improved imaging with X-ray computed tomography (CT) and high-pressure micromodels etched with realistic sandstone roughness and pore networks that improved visualization of oil-recovery mechanisms. The CT-compatible apparatus was invaluable for investigating primary heavy-oil production, multiphase flow in fractured and unfractured media, as well as imbibition. Imbibition and the flow of condensed steam are important parts of the thermal recovery process. The high-pressure micromodels were used to develop a conceptual and mechanistic picture of primary heavy-oil production by solution gas drive. They allowed for direct visualization of ...
Date: December 31, 2003
Creator: Kovscek, Anthony R. & Castanier, Louis M.
Partner: UNT Libraries Government Documents Department

Advances in diagnostic instrumentation

Description: Developments in medical imaging in the last ten years are described. Techniques include fine focus x-ray tubes, computerized tomography, emission tomography, and ultrasonography. (ACR)
Date: January 1, 1980
Creator: Perez-Mendez, V.
Partner: UNT Libraries Government Documents Department

Microcomputers and nondestructive test systems

Description: Microcomputers are finding their way into Nondestructive Testing (NDT) Systems. They can be used for scanning system motion control, instrumentation control, data acquisition, data display, and data analysis. This paper describes the application of the Digital Equipment Corporation (DEC), LSI-11 series microcomputers in systems developed and used by the NDT Unit of the Los Alamos National Laboratory. These systems are used for ultrasonic testing and industrial computerized tomography. In some systems more than one microcomputer is used with one acting as a slave to the controlling or master unit. This becomes necessary when the single processor is not capable of handling all required tasks within the interval between data samples or other time constraints. The systems can be interfaced to a variety of NDT instrumentation. If the instrument has a digital command interface, then data and commands are passed back and forth through this interface. Frequently, the NDT instrumentation used does not have a digital capability and has only analog outputs. A general purpose interface has been designed and built to accept and digitize these inputs and to also display data on a storage cathode ray tube display. The systems contain translator circuits to drive stepper motors. While each system is normally coupled to a specific scanning device, its use is not restricted to only that scanner since the system can be easily programmed to drive other motors or scanners. Motors of almost any size or torque rating can be used without changing anything in the basic control system. A translator card and adequate power supply are the only changes that might be required, and a software change might also be required to keep the motor speed within its operating limits. Therefore, special purpose fixtures can be designed, built, and interfaced to the control system to perform inspections of special ...
Date: January 1, 1983
Creator: Strong, R.D.
Partner: UNT Libraries Government Documents Department

Positron emission tomography of the heart

Description: Positron emission computed tomography (PCT) represents an important new tool for the noninvasive evaluation and, more importantly, quantification of myocardial performance. Most currently available techniques permit assessment of only one aspect of cardiac function, i.e., myocardial perfusion by gamma scintillation camera imaging with Thallium-201 or left ventricular function by echocardiography or radionuclide angiocardiography. With PCT it may become possible to study all three major segments of myocardial performance, i.e., regional blood flow, mechanical function and, most importantly, myocardial metabolism. Each of these segments can either be evaluated separately or in combination. This report briefly describes the principles and technological advantages of the imaging device, reviews currently available radioactive tracers and how they can be employed for the assessment of flow, function and metabolism; and, lastly, discusses possible applications of PCT for the study of cardiac physiology or its potential role in the diagnosis of cardiac disease.
Date: January 1, 1979
Creator: Schelbert, H.R.; Phelps, M.E. & Kuhl, D.E.
Partner: UNT Libraries Government Documents Department

Simulation and preliminary performance characteristics of a computed tomography device for industrial applications

Description: A computed tomography system designed to function in an industrial environment is being constructed. The modular design maintains the flexibility necessary in an environment where source strength and energy, as well as detector type, could change with each application. The static nature of industrial objects also allow economies of design not possible where dynamic objects are to be analyzed. Simulation of the device has been completed and expected image qualities obtained.
Date: January 1, 1978
Creator: Kruger, R.P.; Cannon, T.M.; Lundy, A.S. & Morris, R.A.
Partner: UNT Libraries Government Documents Department

Development of Nuclear Magnetic Resonance Imaging/spectroscopy for improved petroleum recovery. Final report

Description: The overall objectives of this program are to develop and apply Nuclear Magnetic Resonance Imaging (NMRI) and CT X-Ray Scanning methods for determining rock, fluid, and petrophysical properties and for fundamental studies of multiphase flow behavior in porous media. Specific objectives are divided into four subtasks: (1) development of NMRI and CT scanning for the determination of rock-fluid and petrophysical properties; (2) development of NMRI and CT scanning for characterizing conventional multiphase displacement processes; (3) development of NMR and CT scanning for characterizing dispersed phase processes; and (4) miscible displacement studies.
Date: April 1, 1994
Creator: Barrufet, M. A.; Flumerfelt, F. W.; Walsh, M. P. & Watson, A. T.
Partner: UNT Libraries Government Documents Department

Emission and transmission noise propagation in positron emission computed tomography

Description: Errors in positron emission computed tomograms are the result of noise propagated from three sources: (1) the statistical fluctuation in the positron coincidence events; (2) the statistical fluctuation in the incident transmission beam; and (3) the statistical fluctuation in the transmitted beam. The data for the transmission study in (2) and (3) are used to compensate for internal absorption of the distributed positron source. For the reconstruction of a circular phantom using the convolution algorithm, the percent root-mean-square uncertainty (%RMS) is related to the total measured positron events C and the incident photon flux per cm I/sub 0/. Our derivation of the %RMS uncertainty based on the propagation of errors yields a simple expression: %RMS = ..sqrt..K/sub 1//C + K/sub 2//I/sub 0/. The constants K/sub 1/ = 4.52 x 10/sup 8/ and K/sub 2/ = 1.48 x 10/sup 8/ were determined for a 20 cm diameter disc based on computer simulation. The projection data were analytically calculated with an attenuation coefficient ..mu.. = 0.0958 cm/sup -1/ for 140 angles between 0 and ..pi... Poisson noise was added to the positron coincidence events, the incident transmission events I/sub 0/, and the transmitted events. These results indicate that for a total number of incident transmission photons per cm of 2.0 x 10/sup 5/, the contrast resolution for a fixed spatial resolution is limited to 27% even with an infinite number of emission events. For a total of 10/sup 6/ emission events the contrast resolution is 34%.
Date: June 1, 1979
Creator: Gullberg, G.T. & Huesman, R.H.
Partner: UNT Libraries Government Documents Department

Estimating the risk associated with computerized tomography doses

Description: The largest annual whole- body dose to the US population from man-made radiation is from medical sources. According to the BEIR report, the use of diagnostic x-rays by the medical profession has increased in recent years at an annual rate of 1 to 4%. Risk factors developed by the BEIR committee can be used to estimate the risk to the population due to the exposure incurred through medical radiography. In this paper, these risk factors are employed to obtain an estimate of risk due to radiation exposure from computerized tomography (CT).
Date: January 1, 1979
Creator: Yalcintas, M.G.; Leggett, R.W.; Dunning, D.E. & Nalcioglu, O.
Partner: UNT Libraries Government Documents Department

A pipelined IC architecture for radon transform computations in a multiprocessor array

Description: The amount of data generated by CT scanners is enormous, making the reconstruction operation slow, especially for 3-D and limited-data scans requiring iterative algorithms. The Radon transform and its inverse, commonly used for CT image reconstruction from projections, are computationally burdensome for today's single-processor computer architectures. If the processing times for the forward and inverse Radon transforms were comparatively small, a large set of new CT algorithms would become feasible, especially those for 3-D and iterative tomographic image reconstructions. In addition to image reconstruction, a fast Radon Transform Computer'' could be naturally applied in other areas of multidimensional signal processing including 2-D power spectrum estimation, modeling of human perception, Hough transforms, image representation, synthetic aperture radar processing, and others. A high speed processor for this operation is likely to motivate new algorithms for general multidimensional signal processing using the Radon transform. In the proposed workshop paper, we will first describe interpolation schemes useful in computation of the discrete Radon transform and backprojection and compare their errors and hardware complexities. We then will evaluate through statistical means the fixed-point number system required to accept and generate 12-bit input and output data with acceptable error using the linear interpolation scheme selected. These results set some of the requirements that must be met by our new VLSI chip architecture. Finally we will present a new unified architecture for a single-chip processor for computing both the forward Radon transform and backprojection at high data rates. 3 refs., 2 figs.
Date: May 25, 1990
Creator: Agi, I.; Hurst, P.J. & Current, K.W. (California Univ., Davis, CA (USA). Dept. of Electrical Engineering and Computer Science)
Partner: UNT Libraries Government Documents Department

CT reconstruction from limited projection angles

Description: When the available CT projection data are incomplete, there exists a null space in the space of possible reconstructions about which the data provide no information. Deterministic CT reconstructions are impotent in regard to this null space. Furthermore, it is shown that consistency conditions based on projection moments do not provide the missing projections. When the projection data consist of a set of parallel projections that do not encompass a complete 180/sup 0/ rotation, the null space corresponds to a missing sector in the Fourier transform of the original 2-D function. The long-range streak artifacts created by the missing sector can be reduced by attenuating the Fourier transform of the reconstruction smoothly to zero at the sector boundary. It is shown that the Fourier transform of a reconstruction obtained under a maximum entropy constraint is nearly zero in the missing sector. Hence, maximum entropy does not overcome the basic lack of information. It is suggested that some portion of the null space might be filled in by use of a priori knowledge of the type of image expected.
Date: January 1, 1982
Creator: Hanson, K.M.
Partner: UNT Libraries Government Documents Department

Axial tomography from digitized real time radiography

Description: Axial tomography from digitized real time radiographs provides a useful tool for industrial radiography and tomography. The components of this system are: x-ray source, image intensifier, video camera, video line extractor and digitizer, data storage and reconstruction computers. With this system it is possible to view a two dimensional x-ray image in real time at each angle of rotation and select the tomography plane of interest by choosing which video line to digitize. The digitization of a video line requires less than a second making data acquisition relatively short. Further improvements on this system are planned and initial results are reported.
Date: January 18, 1985
Creator: Zolnay, A.S.; McDonald, W.M.; Doupont, P.A.; McKinney, R.L. & Lee, M.M.
Partner: UNT Libraries Government Documents Department

Radiographic study of impact in polymer-bonded explosives

Description: Computer-tomography generated material-density maps from flash x-ray radiographs of the impact of cylinders of mockup polymer-bonded explosive (PBX) striking a steel plate. Comparison of the density fields with computer simulation allowed discrimination of rather complex deformation and flow models for insensitive explosives to be used in further studies of chemical reactions initiated by shock waves.
Date: January 1, 1981
Creator: Fugelso, E.; Jacobson, J.D.; Karpp, R.R. & Jensen, R.
Partner: UNT Libraries Government Documents Department