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Geometric effects in tomographic reconstruction

Description: In x-ray and ion-beam computerized tomography, there are a number of reconstruction effects, manifested as artifacts, that can be attributed to the geometry of the experimental setup and of the object being scanned. In this work, we will examine four geometric effects that are common to first-and third-generation (parallel beam, 180 degree) computerized tomography (CT) scanners and suggest solutions for each problem. The geometric effects focused on in this paper are: X-pattern'' artifacts (believed to be caused by several errors), edge-generated ringing artifacts (due to improper choice of the reconstruction filter and cutoff frequency), circular-ring artifacts (caused by employing uncalibrated detectors), and tuning-fork artifacts (generated by an incorrectly specified center-of-rotation). Examples of four effects are presented. The X-pattern and edge-generated ringing artifacts are presented with actual experimental data introducing the artifact. given the source of the artifact, we present simulated data designed to replicate the artifact. Finally, we suggest ways to reduce or completely remove these artifacts. The circular-ring and tuning-fork artifacts are introduced with actual experimental data as well, while digital signal processing solutions are employed to remove the artifacts from the data. 15 refs., 12 figs.
Date: January 8, 1990
Creator: Barnes, F.L.; Azevedo, S.G.; Martz, H.E. Jr.; Roberson, G.P.; Schneberk, D.J. & Skeate, M.F.
Partner: UNT Libraries Government Documents Department

Report of the CEBAF PAC4 Subcomittee on STAR

Description: This report discusses the following topics: the symmetric toroidal array (STAR) spectrometer facility; investigation of the N {yields} {Delta} transition; Hyperon production in the (e, e{prime}k) reactions; investigation of few-body systems with the (e, e{prime}p) reaction; nuclear structure studies with the (e,e{prime}pp) reaction; Measurement of G{sub Em} in a recoil polarimetry measurement; parity violation measurements; and STAR design and performance.
Date: August 8, 1990
Creator: Barnes, P.D.
Partner: UNT Libraries Government Documents Department

[Letter from Cassandra Broadus to Sylvia Russell, November 8, 1990]

Description: Photocopy of a letter from Cassandra Broadus, North Texas Institute for Educators on the Visual Arts, to Sylvia Russell, Pilot Point Art Supervisor. In regards to Broadus modeling a DBAE, discipline-based art education, lesson for the teachers and participants at the meeting in Pilot Point and hoping they picked up something they will be able to use for their own classrooms. Broadus ends the letter with details about the upcoming visitation with a man named Vicente, for a "Potter on the Porch" lesson.
Date: November 8, 1990
Creator: Broadus, Cassandra
Partner: UNT Libraries Special Collections

[University of North Texas Getty Project Matching Funds]

Description: A report, written by the Office of Advancement, to outline their progress towards matching the funds necessary as stated by the Getty Center for Education in the Arts, to proceed with the Educational Reform Program, North Texas Institute for Educators on the Visual Arts. The list is separated into three factions, Pending, Resubmitted and New as the program continues to seek support and meet their goal.
Date: August 8, 1990
Creator: Burton, Bruce M.
Partner: UNT Libraries Special Collections

[Letter from Jack Davis to Jim Muro and Mark Elder, October 8, 1990]

Description: Photocopy of a letter from Jack Davis, co-director of North Texas Institute for Educators on the Visual Arts to Jim Muro and Mark Elder, in regards to the Amon G. Carter Foundation matching a grant provided by the Getty Center for Education in the Arts. The letter goes into details of how the grant money will be divided into three different payments over the course of three years, so that it is consistent with the payment provided by the Getty Center. Included in the letter to Muro and Elder, Davis has attached a letter he has written to Vicki Rosenberg, Program Officer for the Getty Center, with details about payment plans as devised by the Center. cc'd on the letter, Bill McCarter, Bruce Burton, Scott Sullivan, and Rollie Schafer.
Date: October 8, 1990
Creator: Davis, Donald Jack
Partner: UNT Libraries Special Collections

[RE: Report on Directors Affinity Group Meeting, Chatanooga]

Description: A memo from Jack Davis, co-director of North Texas Institute for Educators on the Visual Arts, to the Institute Directors. The memo is in regards to a draft report on the Directors' Affinity Group Meeting in Chattanooga. David requests they review and let him know if its represented accurately.
Date: March 8, 1990
Creator: Davis, Donald Jack
Partner: UNT Libraries Special Collections

A 3d particle simulation code for heavy ion fusion accelerator studies

Description: We describe WARP, a new particle-in-cell code being developed and optimized for ion beam studies in true geometry. We seek to model transport around bends, axial compression with strong focusing, multiple beamlet interaction, and other inherently 3d processes that affect emittance growth. Constraints imposed by memory and running time are severe. Thus, we employ only two 3d field arrays ({rho} and {phi}), and difference {phi} directly on each particle to get E, rather than interpolating E from three meshes; use of a single 3d array is feasible. A new method for PIC simulation of bent beams follows the beam particles in a family of rotated laboratory frames, thus straightening'' the bends. We are also incorporating an envelope calculation, an (r, z) model, and 1d (axial) model within WARP. The BASIS development and run-time system is used, providing a powerful interactive environment in which the user has access to all variables in the code database. 10 refs., 3 figs.
Date: June 8, 1990
Creator: Friedman, A.; Bangerter, R.O.; Callahan, D.A.; Grote, D.P.; Langdon, A.B. (Lawrence Livermore National Lab., CA (USA)) & Haber, I. (Naval Research Lab., Washington, DC (USA))
Partner: UNT Libraries Government Documents Department

(International Collaboration on Advanced Neutron Sources)

Description: The International Collaboration on Advanced Neutron Sources was started about a decade ago with the purpose of sharing information throughout the global neutron community. The collaboration has been extremely successful in optimizing the use of resources, and the discussions are open and detailed, with reasons for failure shared as well as reasons for success. Although the meetings have become increasingly oriented toward pulsed neutron sources, many of the neutron instrumentation techniques, such as the development of better monochromators, fast response detectors and various data analysis methods, are highly relevant to the Advanced Neutron Source (ANS). I presented one paper on the ANS, and another on the neutron optical polarizer design work which won a 1989 R D-100 Award. I also gained some valuable design ideas, in particular for the ANS hot source, in discussions with individual researchers from Canada, Western Europe, and Japan.
Date: November 8, 1990
Creator: Hayter, J.B.
Partner: UNT Libraries Government Documents Department

A Status Report of Hawaiian Hawk Nesting Activities at the Proposed Well Site No. 2

Description: On August 11, 1990 during an ornithological survey at the True/Mid Pacific Geothermal Venture proposed well site No.2, a Hawaiian hawk (Buteo solitarius) nest with a nestling was found approximately 430 feet from the proposed well pad clearing. The U.S. Fish and Wildlife Service and the State of Hawaii have listed the Hawaiian hawk as an endangered species. Future development in this area could be impacted by the presence of this endangered avian species and its nest in such close proximity to the proposed well site. This report summarizes the results of observations at the nest on August 12, 19 and 25 and September 2, 1990.
Date: September 8, 1990
Creator: Jeffrey, Jack
Partner: UNT Libraries Government Documents Department

[News Clip: 2 Live Crew]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 5:30 P.M.
Date: July 8, 1990
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: 14-1]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 10 P.M.
Date: August 8, 1990
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: 14-1]

Description: B-roll video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date: August 8, 1990, 10:00 p.m.
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: 14-1]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 6pm.
Date: November 8, 1990, 6:00 p.m.
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: 14-1]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas to accompany a news story. This story aired at 6pm.
Date: December 8, 1990, 6:00 p.m.
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: Alamo weekend]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 5:30 P.M.
Date: July 8, 1990
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: Arts District]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 6 P.M.
Date: March 8, 1990
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: Band Contest]

Description: B-roll video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date: October 8, 1990, 10:00 p.m.
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: Bartlett]

Description: Video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story. This story aired at 6 P.M.
Date: August 8, 1990
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections

[News Clip: Bartlett]

Description: B-roll video footage from the KXAS-TV/NBC station in Fort Worth, Texas, to accompany a news story.
Date: August 8, 1990, 6:00 p.m.
Creator: KXAS-TV (Television station : Fort Worth, Tex.)
Partner: UNT Libraries Special Collections