Corrosion and mass transport processes in Carbon steel miniature waste packages

In this study, we have systematically investigated corrosion and mass transport processes in carbon steel miniature waste packages (MWP) in dynamic systems (water in, water out) under varying chemical conditions. The MWP were fabricated to have similar configuration to the DOE Spent Nuclear Fuel (SNF) waste package and that individual components to be in scale with each other compare to the SNF waste package. Two MWP configurations were studied: a bathtub model and a flow-through model. By slowly dripping 4 different solutions (groundwater obtained from well water J-13 located near Yucca Mountain, and J-13 water adjusted to low-pH, high-salinity, and high salinity-high nitrate) into the MWP, we were able to investigate the manner of oxidation, identify transported minerals contained in the effluent, and characterize the mass transport in terms of particle size. Manner of oxidation. Through time-lapse digital photography, we were able to document the process of corrosion within a glass walled MWP. Formation of colored corrosion products including short-lived colored complexes was noted. A sequence of possible corrosion products was proposed. The availability of oxygen and limitation of diffusion through corrosion products lowers the rate of the corrosion process. In most cases the MWP exit hole sealed within 4 weeks of water introduction, resulting in overflow from the top of the MWP. This self-sealing is likely due to the larger molar volume of the corrosion products. The overflow water traveled on the outer surface of the MWP and hung at bottom before dripping out. Under these conditions corrosion to the bottom of the MWP was observed and eventual bottom failure is likely. It is recommended an addition of a skirt to the actual waste packages to deflect water away from the waste package. Identification of Transported Minerals. Through X-Ray Diffraction and Scanning Electron Microscopy studies of solids in the MWP effluent, we discovered that secondary minerals, such as goethite were prevalent. Many of these corrosion products were amorphous and would expect to have different properties (buffering, sorption) compared to more crystalline minerals. Individual particles ranged from about 0.2 to 0.8 (J,m in diameter and larger conglomerates of particles up to several um in diameter were also present. Mass Transport of Solids. The greatest mass of solids transported out of the MWP occurred under acidic conditions followed by the control (J-13) solution. The salt (high ionic strength) solutions were more variable due to experimental difficulties but appear not to enhance the corrosion process. The nature of the transported material also differed by solution-type. As expected, most of the iron (\u3e80%) was found in the dissolved state under acidic conditions, while solids (\u3e0.45um in diameter) dominated in the effluent of the other solutions

Comparison of Vanadium Oxide Catalysts for Synthesis of Benzene: Benzene Purity, Yields and Reconditioning Methods

From the 16th International Radiocarbon Conference held in Gronigen, Netherlands, June 16-20, 1997.This study compares vanadium oxide catalysts from three different sources: Noakes (N), Harshaw Chemical (H) and Kh. Arslanov at the St. Petersburg State University, Russia (R). The catalysts are used to convert acetylene to benzene in the last step of benzene synthesis. The organic purity of benzene in all three catalysts is high; 99.91-99.93% for (N) and (H) and 99.87% for (R). The benzene yields range from 90.0 to 94.3%. (N) averaged 92.6%, (H) averaged 91.1% and (R) averaged 92.0%. A conversion residue in the catalysts was analyzed for delta-13C and found to be isotopically lighter relative to acetylene by -2.2 per mil for (N) and (H) and -3.9 per mil for (R). Benzene yields were studied on different reconditioning methods applied to all catalysts: heating to 400 degrees C in air averaged 92.3%; the same temperature with a half and half mixture of O2 and Ar averaged 91.9%, adding a half and half mixture of H2 and Ar at 200 degrees C to the end of this treatment averaged 91.8%. Based on this research, the obvious difference seen between the catalysts is in their trace by-products.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Comparison of Vanadium Oxide Catalysts for Synthesis of Benzene: Benzene Purity, Yields and Reconditioning Methods

From the 16th International Radiocarbon Conference held in Gronigen, Netherlands, June 16-20, 1997.This study compares vanadium oxide catalysts from three different sources: Noakes (N), Harshaw Chemical (H) and Kh. Arslanov at the St. Petersburg State University, Russia (R). The catalysts are used to convert acetylene to benzene in the last step of benzene synthesis. The organic purity of benzene in all three catalysts is high; 99.91-99.93% for (N) and (H) and 99.87% for (R). The benzene yields range from 90.0 to 94.3%. (N) averaged 92.6%, (H) averaged 91.1% and (R) averaged 92.0%. A conversion residue in the catalysts was analyzed for delta-13C and found to be isotopically lighter relative to acetylene by -2.2 per mil for (N) and (H) and -3.9 per mil for (R). Benzene yields were studied on different reconditioning methods applied to all catalysts: heating to 400 degrees C in air averaged 92.3%; the same temperature with a half and half mixture of O2 and Ar averaged 91.9%, adding a half and half mixture of H2 and Ar at 200 degrees C to the end of this treatment averaged 91.8%. Based on this research, the obvious difference seen between the catalysts is in their trace by-products.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Fréchet distance with speed limits

In this paper, we introduce a new generalization of the well-known Fréchet distance between two polygonal curves, and provide an efficient algorithm for computing it. The classical Fréchet distance between two polygonal curves corresponds to the maximum distance between two point objects that traverse the curves with arbitrary non-negative speeds. Here, we consider a problem instance in which the speed of traversal along each segment of the curves is restricted to be within a specified range. We provide an efficient algorithm that decides in O(n2 logn) time whether the Fréchet distance with speed limits between two polygonal curves is at most ?, where n is the number of segments in the curves, and ≈ ≤0 is an input parameter. We then use our solution to this decision problem to find the exact Fréchet distance with speed limits in O(n2 log2 n) time

Improved algorithms for partial Curve matching

Back in 1995, Alt and Godau gave an efficient algorithm for deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm log(nm)), for n and m being the number of segments in the two curves, respectively. We improve this long-standing result by presenting an algorithm that solves this decision problem in O(nm) time. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems. We also improve the map matching algorithm of Alt et al. for the case when the map is a directed acyclic graph

Improved algorithms for partial curve matching

We revisit the problem of deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm), for n and m being the number of segments in the two curves. This improves the long-standing result of Alt and Godau by an O(log(nm)) factor. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems. We also improve the map matching algorithm of Alt et al. for the particular case in which the map is a directed acyclic graph

Characterization and optical properties of mechanochemically synthesized molybdenum-doped rutile nanoparticles and their electronic structure studies by density functional theory

The optical and electronic properties of molybdenum (Mo) doped rutile TiO2 prepared by the mechanochemical method were studied both experimentally and using density functional theory (DFT). The synthesized nanoparticles were characterized by XRD, TEM, EDS-MAP, and XPS. The XRD results showed the successful incorporation of Mo in the rutile crystal lattice. High-resolution TEM images illustrated a decreasing trend in the (110) d-spacing for samples doped up to 3 at%. The shift toward higher binding energies in the XPS spectra was due to the higher oxidization tendencies of Mo5+ and Mo6+ substituted in Ti4+ sites. The optical behavior of samples was examined by UV–Vis and photoluminescence spectroscopy. The bandgap energy value of rutile was reduced from 3.0 eV to 2.4 eV by 2 at% Mo doping. The DFT calculations showed a reduction of bandgap energy value of rutile to 2.35 eV with 2 at% Mo, which is in harmony with the experimental results. The creation of energy states below the conduction band because of Mo doping was identified as the reason for reducing the bandgap energy and photoluminescence emission of rutile