The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Chick C. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Multiple Data Set rietveld analysis using isotopes in powder neutron diffraction 2 positional and anisotropic thermal displacement parameter determinations in cuo tenorite at 2 k and 300 k
Journal of Applied Crystallography, 2003Co-Authors: Paul F. Henry, Mark T. Weller, Harriott Nowell, Chick C. WilsonAbstract:The technique of isotope-substitution neutron diffraction (ISND) and combined-Data-Set Rietveld analysis from powder neutron Data of crystalline materials is presented and compared with single-Data-Set powder refinement methods. The rationale behind improvements in the precision and accuracy of the refined model as a result of reduction in parameter correlation in the least-squares technique is described. The improvements are demonstrated practically through a study of isotopically copper-substituted tenorite, CuO, at 2 and 300 K. Typically, the estimated errors on structural parameters from the combined analysis technique are 30% lower than separate single-Data-Set analyses. Comparison of the precision and accuracy of the structural models obtained from this investigation with previous single-crystal X-ray studies are also presented.
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Multiple-Data-Set Rietveld analysis using isotopes in powder neutron diffraction. I. Accurate determination of the doping level in the ternary system NixMg1-xO, 0.005 < x < 0.1
Journal of Applied Crystallography, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The use of isotopes to extract precise and very accurate structural information in complex Rietveld analysis has been demonstrated by comparison of results obtained for single-Data-Set analysis with those from Multiple-Data-Set single-crystallographic-model analysis of NixMg1−xO doped with various nickel isotopes. Fractional occupancies of dopants can be accurately determined down to at least the 0.5% doping level, which cannot be obtained through single-sample-Data-Set refinements because of correlation effects, even when a large contrast exists between the nickel isotope used and magnesium.
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Structural investigation of TS-1: determination of the true nonrandom titanium framework substitution and silicon vacancy distribution from powder neutron diffraction studies using isotopes
The Journal of Physical Chemistry B, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The first complete investigation of the structure of the selective oxidation catalyst TS-1 is presented. Constant wavelength powder neutron diffraction Data collected on isotopically substituted titanium silicalite (TS-1) samples, with a Si:Ti molar ratio of 39:1, have been studied using a combination of single and Multiple Data Set Rietveld analysis exploiting the scattering length contrast between the different titanium isotopes and silicon. This has allowed both the silicon vacancy and titanium site substitution distributions to be determined, which has not been possible previously. Both distributions are found to be nonrandom with the titanium preferentially substituting on 3 of the 12 crystallographically independent framework sitesT8, T10 and T3 (in order of decreasing titanium content)and silicon vacancies on 2 framework sitesT1 and T5. This study illustrates the power of isotopic substitution in powder neutron diffraction experiments to yield enhanced structural information in complex systems.
Paul F. Henry - One of the best experts on this subject based on the ideXlab platform.
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Multiple Data Set rietveld analysis using isotopes in powder neutron diffraction 2 positional and anisotropic thermal displacement parameter determinations in cuo tenorite at 2 k and 300 k
Journal of Applied Crystallography, 2003Co-Authors: Paul F. Henry, Mark T. Weller, Harriott Nowell, Chick C. WilsonAbstract:The technique of isotope-substitution neutron diffraction (ISND) and combined-Data-Set Rietveld analysis from powder neutron Data of crystalline materials is presented and compared with single-Data-Set powder refinement methods. The rationale behind improvements in the precision and accuracy of the refined model as a result of reduction in parameter correlation in the least-squares technique is described. The improvements are demonstrated practically through a study of isotopically copper-substituted tenorite, CuO, at 2 and 300 K. Typically, the estimated errors on structural parameters from the combined analysis technique are 30% lower than separate single-Data-Set analyses. Comparison of the precision and accuracy of the structural models obtained from this investigation with previous single-crystal X-ray studies are also presented.
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Multiple-Data-Set Rietveld analysis using isotopes in powder neutron diffraction. I. Accurate determination of the doping level in the ternary system NixMg1-xO, 0.005 < x < 0.1
Journal of Applied Crystallography, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The use of isotopes to extract precise and very accurate structural information in complex Rietveld analysis has been demonstrated by comparison of results obtained for single-Data-Set analysis with those from Multiple-Data-Set single-crystallographic-model analysis of NixMg1−xO doped with various nickel isotopes. Fractional occupancies of dopants can be accurately determined down to at least the 0.5% doping level, which cannot be obtained through single-sample-Data-Set refinements because of correlation effects, even when a large contrast exists between the nickel isotope used and magnesium.
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Structural investigation of TS-1: determination of the true nonrandom titanium framework substitution and silicon vacancy distribution from powder neutron diffraction studies using isotopes
The Journal of Physical Chemistry B, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The first complete investigation of the structure of the selective oxidation catalyst TS-1 is presented. Constant wavelength powder neutron diffraction Data collected on isotopically substituted titanium silicalite (TS-1) samples, with a Si:Ti molar ratio of 39:1, have been studied using a combination of single and Multiple Data Set Rietveld analysis exploiting the scattering length contrast between the different titanium isotopes and silicon. This has allowed both the silicon vacancy and titanium site substitution distributions to be determined, which has not been possible previously. Both distributions are found to be nonrandom with the titanium preferentially substituting on 3 of the 12 crystallographically independent framework sitesT8, T10 and T3 (in order of decreasing titanium content)and silicon vacancies on 2 framework sitesT1 and T5. This study illustrates the power of isotopic substitution in powder neutron diffraction experiments to yield enhanced structural information in complex systems.
Mark T. Weller - One of the best experts on this subject based on the ideXlab platform.
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Multiple Data Set rietveld analysis using isotopes in powder neutron diffraction 2 positional and anisotropic thermal displacement parameter determinations in cuo tenorite at 2 k and 300 k
Journal of Applied Crystallography, 2003Co-Authors: Paul F. Henry, Mark T. Weller, Harriott Nowell, Chick C. WilsonAbstract:The technique of isotope-substitution neutron diffraction (ISND) and combined-Data-Set Rietveld analysis from powder neutron Data of crystalline materials is presented and compared with single-Data-Set powder refinement methods. The rationale behind improvements in the precision and accuracy of the refined model as a result of reduction in parameter correlation in the least-squares technique is described. The improvements are demonstrated practically through a study of isotopically copper-substituted tenorite, CuO, at 2 and 300 K. Typically, the estimated errors on structural parameters from the combined analysis technique are 30% lower than separate single-Data-Set analyses. Comparison of the precision and accuracy of the structural models obtained from this investigation with previous single-crystal X-ray studies are also presented.
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Multiple-Data-Set Rietveld analysis using isotopes in powder neutron diffraction. I. Accurate determination of the doping level in the ternary system NixMg1-xO, 0.005 < x < 0.1
Journal of Applied Crystallography, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The use of isotopes to extract precise and very accurate structural information in complex Rietveld analysis has been demonstrated by comparison of results obtained for single-Data-Set analysis with those from Multiple-Data-Set single-crystallographic-model analysis of NixMg1−xO doped with various nickel isotopes. Fractional occupancies of dopants can be accurately determined down to at least the 0.5% doping level, which cannot be obtained through single-sample-Data-Set refinements because of correlation effects, even when a large contrast exists between the nickel isotope used and magnesium.
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Structural investigation of TS-1: determination of the true nonrandom titanium framework substitution and silicon vacancy distribution from powder neutron diffraction studies using isotopes
The Journal of Physical Chemistry B, 2001Co-Authors: Paul F. Henry, Mark T. Weller, Chick C. WilsonAbstract:The first complete investigation of the structure of the selective oxidation catalyst TS-1 is presented. Constant wavelength powder neutron diffraction Data collected on isotopically substituted titanium silicalite (TS-1) samples, with a Si:Ti molar ratio of 39:1, have been studied using a combination of single and Multiple Data Set Rietveld analysis exploiting the scattering length contrast between the different titanium isotopes and silicon. This has allowed both the silicon vacancy and titanium site substitution distributions to be determined, which has not been possible previously. Both distributions are found to be nonrandom with the titanium preferentially substituting on 3 of the 12 crystallographically independent framework sitesT8, T10 and T3 (in order of decreasing titanium content)and silicon vacancies on 2 framework sitesT1 and T5. This study illustrates the power of isotopic substitution in powder neutron diffraction experiments to yield enhanced structural information in complex systems.
Kleanthis Psarris - One of the best experts on this subject based on the ideXlab platform.
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Accelerating Matrix Operations with Improved Deeply Pipelined Vector Reduction
IEEE Transactions on Parallel and Distributed Systems, 2012Co-Authors: Chia-tien Dan Lo, Kleanthis PsarrisAbstract:Many scientific or engineering applications involve matrix operations, in which reduction of vectors is a common operation. If the core operator of the reduction is deeply pipelined, which is usually the case, dependencies between the input Data elements cause Data hazards. To tackle this problem, we propose a new reduction method with low latency and high pipeline utilization. The performance of the proposed design is evaluated for both single Data Set and Multiple Data Set scenarios. Further, QR decomposition is used to demonstrate how the proposed method can accelerate its execution. We implement the design on an FPGA and compare its results to other methods.
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Multiple Data Set reduction on fpgas
Field-Programmable Technology, 2010Co-Authors: Yigang Tai, Kleanthis PsarrisAbstract:Many scientific or engineering applications perform reduction of Sets of sequential Data streams. If the core operator of the reduction is deeply pipelined, dependencies between the input Data elements cause Data hazards in the pipeline. To tackle this problem, we propose a Multiple Set variable length reduction design with low latency and high pipeline utilization in this paper. We prove the buffer size and execution time bounds, and then show its performance on practical Multiple Data Set scenarios. We apply the proposed method to the Householder QR decomposition and compare its performance to other methods with superior results. The proposed design is implemented on FPGAs with resource usage and performance presented.
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FPT - Multiple Data Set reduction on FPGAs
2010 International Conference on Field-Programmable Technology, 2010Co-Authors: Yigang Tai, Kleanthis PsarrisAbstract:Many scientific or engineering applications perform reduction of Sets of sequential Data streams. If the core operator of the reduction is deeply pipelined, dependencies between the input Data elements cause Data hazards in the pipeline. To tackle this problem, we propose a Multiple Set variable length reduction design with low latency and high pipeline utilization in this paper. We prove the buffer size and execution time bounds, and then show its performance on practical Multiple Data Set scenarios. We apply the proposed method to the Householder QR decomposition and compare its performance to other methods with superior results. The proposed design is implemented on FPGAs with resource usage and performance presented.
Masaki Horiuchi - One of the best experts on this subject based on the ideXlab platform.
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EXAFS study of doped ceria using Multiple Data Set fit
Solid State Ionics, 2005Co-Authors: Hiroshi Deguchi, Hiroyuki Yoshida, Toru Inagaki, Masaki HoriuchiAbstract:Abstract EXAFS analysis was applied to ceria compounds doped with Gd3+, Y3+ and La3+. Although several studies using EXAFS have been reported, their analysis was limited only to the nearest neighbor shell. We analyzed the next nearest neighbor shell using “Multiple Data Set fit” method, where two EXAFS Data Sets of the same sample around Ce4+ and dopant cation were fitted at the same time. Based on the EXAFS results, local structure of the doped ceria compounds was discussed. It was found that Y3+ and La3+ had a strong tendency to get together and formed a dopant-rich cluster including oxygen vacancies, whereas Gd3+ did not gather and distributed randomly in ceria lattice.
