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We study the class of rectilinear polygons, calledX – Y polygons, with horizontal and vertical edges, which are frequently used as building blocks for very large-scale integrated (VLSI) circuit layout and wiring. In the paper we introduce the notion of convexity within the class ofX – Y polygons and present efficient algorithms for computing theX – Y convex hulls of anX – Y polygon and of a set ofX – Y polygons under various conditions. Unlike convex hulls in the Euclidean plane, theX – Y convex hull of a set ofX – Y polygons may not exist. The condition under which theX – Y convex hull exists is given and an algorithm for testing if the given set ofX – Y polygons satisfies the condition is also presented. 相似文献
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Varga Zsolt Wallenius Maria Nicholl Adrian Mayer Klaus Balan Ionel Benea Vasile 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1585-1591
JRC-Karlsruhe obtained a swipe sample from a highly enriched uranium seizure, which had taken place in 2011. Due to the very low amount of uranium (nanograms) a new method needed to be developed to determine the U production date (age). The particles on the swipe were collected on a pyrolytic graphite planchet using a vacuum impactor and they were subsequently leached with ccHNO3. The “bulk” U isotopic composition (235U: 72.51?±?0.03 wt%) and the production date (December 1992?±?1 year) determined by MC-ICP-MS indicated that the material showed similarity with two other HEU cases seized earlier in Europe.
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A novel and simple analytical procedure has been developed for the trace-level determination of lanthanides (rare-earth elements) in uranium-bearing materials by inductively coupled plasma sector-field mass spectrometry (ICP-SFMS). The method involves a selective extraction chromatographic separation of lanthanides using TRU™ resin followed by ICP-SFMS analysis. The limits of detection of the method proposed is in the low pg g−1 range, which are approximately two orders of magnitude better than that of without chemical separation. The method was validated by the measurement of reference material and applied for the analysis of uranium ore concentrates (yellow cakes) for nuclear forensic purposes, as a potential application of the methodology. 相似文献
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Kerst Thomas Sand Johan Ihantola Sakari Peräjärvi Kari Nicholl Adrian Hrnecek Erich Toivonen Harri Toivonen Juha 《Optical Review》2018,25(3):429-436
Optical Review - This paper presents the remote detection of alpha contamination in a nuclear facility. Alpha-active material in a shielded nuclear radiation containment chamber has been localized... 相似文献
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Zsolt Varga Adrian Nicholl Erich Hrnecek Maria Wallenius Klaus Mayer 《Journal of Radioanalytical and Nuclear Chemistry》2018,318(3):1565-1571
The paper describes the age (production date) determination of uranium reference materials using the 231Pa/235U ratio. Direct addition of 237Np in secular equilibrium with its 233Pa daughter was chosen instead of the regular milking of 237Np to avoid possible loss of Pa. Sample preparation consists of a fast, one-step procedure. The developed method using ICP-MS for the measurement of 231Pa is more precise than alpha spectrometry and is applicable for freshly produced low-enriched uranium materials. The measured ages are in good agreement with the reported production dates, thus the 231Pa/235U chronometer can be applied for validation of 230Th/234U in nuclear forensics and safeguards. 相似文献
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Dr. Klaus Mayer Dr. Maria Wallenius Dr. Klaus Lützenkirchen Joan Horta Adrian Nicholl Gert Rasmussen Pieter van Belle Dr. Zsolt Varga Dr. Razvan Buda Dr. Nicole Erdmann Prof. Dr. Jens‐Volker Kratz Prof. Dr. Norbert Trautmann Prof. L. Keith Fifield Dr. Stephen G. Tims Dr. Michaela B. Fröhlich Dr. Peter Steier 《Angewandte Chemie (International ed. in English)》2015,54(45):13452-13456
Here we present a nuclear forensic study of uranium from German nuclear projects which used different geometries of metallic uranium fuel. 3b , 3d , 4 Through measurement of the 230Th/234U ratio, we could determine that the material had been produced in the period from 1940 to 1943. To determine the geographical origin of the uranium, the rare‐earth‐element content and the 87Sr/86Sr ratio were measured. The results provide evidence that the uranium was mined in the Czech Republic. Trace amounts of 236U and 239Pu were detected at the level of their natural abundance, which indicates that the uranium fuel was not exposed to any major neutron fluence. 相似文献