Ajay Joshi - Academia.edu (original) (raw)

Papers by Ajay Joshi

The performance of a processor is limited by the specific bottlenecks that a benchmark exposes wh... more The performance of a processor is limited by the specific bottlenecks that a benchmark exposes while running on that processor. Since the quantification of these bottlenecks can be extremely time-consuming, our prior work proposed using the Plackett and Burman design as a statistically-rigorous, but time- efficient method of determining the processor's most significant performance bottlenecks. In this paper, we use

Proceedings of the 2004 international workshop on System level interconnect prediction - SLIP '04, 2004

2006 IEEE International Symposium on Performance Analysis of Systems and Software, 2006

2010 IEEE/IFIP International Conference on Dependable Systems & Networks (DSN), 2010

Abstract Multi-level cell (MLC) NAND flash memories are very popular storage media because of the... more Abstract Multi-level cell (MLC) NAND flash memories are very popular storage media because of their power efficiency and big storage density. This paper proposes to use nonlinear t-error-correcting codes to replace linear BCH codes for error detection and correction in MLC NAND flash memories. Compared to linear BCH codes with the same bit-error correcting capability t, the proposed codes have less errors miscorrected by all codewords and nearly no undetectable errors. For example, the proposed (8281, 8201, 11 ...

Proceedings of the 21st edition of the great lakes symposium on Great lakes symposium on VLSI - GLSVLSI '11, 2011

2009 IEEE Conference on Computer Vision and Pattern Recognition, 2009

19th International Conference on VLSI Design held jointly with 5th International Conference on Embedded Systems Design (VLSID'06), 2006

2005 Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, 2005

Lecture Notes in Computer Science, 2009

The Journal of Physical Chemistry B, 2006

We report a B3LYP density-functional theory (DFT) analysis of O(2) adsorption on 27 Au(n)M(m) (m,... more We report a B3LYP density-functional theory (DFT) analysis of O(2) adsorption on 27 Au(n)M(m) (m, n = 0-3 and m + n = 2 or 3; M = Cu, Ag, Pd, Pt, and Na) clusters. The LANL2DZ pseudopotential and corresponding double-zeta basis set was used for heavy atoms, while a 6-311+G(3df) basis set was used for Na and O. We employed basis-set superposition error (BSSE) corrections in the electronic adsorption energies at 0 K (deltaE(ads)) and also calculated adsorption thermodynamics at standard conditions (298.15 K and 1 atm), i.e., internal energy of adsorption (deltaU(ads)) and Gibbs free energy of adsorption (deltaG(ads)). Natural Bond Orbital (NBO) analysis showed that all the clusters donated electron density to adsorbed O(2) and we successfully predicted intuitive linear correlations between the NBO charge on adsorbed O(2), O-O bond length, and O-O stretching frequency. Although there was no clear trend in the O(2) binding energy (BE = -deltaE(ads)) on pure and alloy dimers, we found the following interesting trend for trimers: BE (MAu(2)) < BE (M(3)) < or = BE (M(2)Au). The alloy trimers containing only one Au atom are most reactive toward O(2) while those with two Au atoms are least reactive. These trends are discussed in the context of the ensemble effect and coulomb interactions. We found an approximate linear correlation between the O(2) BE and charge transfer to O(2) for all 27 clusters. The clusters having strongly electropositive Na atoms (e.g., Na(3) and Na(2)Au) donated almost one full electron to adsorbed O(2), and the BE is maximum on these clusters. Although O(2) dissociation is likely in such cases, we have restricted this study to trends in the adsorption of molecular O(2) only. We also found an approximate linear correlation between the charge transfer and BE versus energy difference between the bare-cluster HOMO and O(2) LUMOs, which we speculate to be a fundamental descriptor of the reactivity of small clusters toward O(2). Part of the scatter in these correlations is attributed to the differences in the O(2) binding orientations on different clusters (geometric effect). Relatively higher bare-cluster HOMO energy eases the charge transfer to adsorbed O(2) and enhances the reactivity toward O(2). The Frontier Orbital Picture (FOP) is not always useful in predicting the most favorable O(2) binding site on clusters. It successfully predicted the cluster-O(2) ground-state configurations for 10 clusters, but failed for the others. Finally, the energetics of fragmentation suggest that the bare and O(2)-covered clusters reported here are stable.

This paper presents the results of a study in which the case study method was used to sort out th... more This paper presents the results of a study in which the case study method was used to sort out the internal and external conditions that might affect the success of a work site trip reduction program. Investigators attempted to disprove a null hypothesis, stated as "The effectiveness of work site trip reduction programs does not depend on organizational culture." The

The Journal of Physical Chemistry B, 2006

Proceedings 2007 IEEE International Conference on Robotics and Automation, 2007

Page 1. Moving Shadow Detection with Low-and Mid-Level Reasoning Ajay J. Joshi, Stefan Atev, Osam... more Page 1. Moving Shadow Detection with Low-and Mid-Level Reasoning Ajay J. Joshi, Stefan Atev, Osama Masoud, and Nikolaos Papanikolopoulos Dept. of Computer Science and Engineering, University of Minnesota – Twin Cities {ajay,atev,masoud,npapas}@cs.umn.edu ...

The Journal of Physical Chemistry B, 2005

We report a detailed density functional theory (B3LYP) analysis of the gas-phase H2O2 formation f... more We report a detailed density functional theory (B3LYP) analysis of the gas-phase H2O2 formation from H2 and O2 on Au3, Au4+, Au5, and Au5-. We find that H2, which interacts only weakly with the Au clusters, is dissociatively added across the Au-O bond, upon interaction with AunO2. One H atom is captured by the adsorbed O2 to form the hydroperoxy intermediate (OOH), while the other H atom is captured by the Au atom. Once formed, the hydroperoxy intermediate acts as a precursor for the closed-loop catalytic cycle. An important common feature of all the pathways is that the rate-determining step of the catalytic cycle is the second H2 addition to form H2O2. The H2O2 desorption is followed by O2 addition to AunH2 to form the hydroperoxy intermediate, thus leading to the closure of the cycle. On the basis of the Gibbs free energy of activation, out of these four clusters, Au4+ is most active for the formation of the H2O2. The 0 K electronic energy of activation and the DeltaGact at the standard conditions are 12.6 and 16.6 kcal/mol respectively. The natural bond orbital charge analysis suggests that the Au clusters remain positively charged (oxidic) in almost all the stages of the cycle. This is interesting in the context of the recent experimental evidence for the activity of cationic Au in CO oxidation and water-gas shift catalysts. We have also found preliminary evidence for a correlation between the activation barrier for the first H2 addition and the O2 binding energy on the Au cluster. It suggests that the minimum activation barrier for the first H2 addition is expected for the Au clusters with 7.0-9.0 kcal/mol O2 binding energy, i.e., in the midrange of the expected interaction energy. This represents a balance between more favorable H2 dissociation when the Aun-O2 interaction is weaker and high O2 coverage when the interaction is stronger. On the basis of this work, we predict that the hydroperoxy intermediate formation can be both thermodynamically and kinetically viable only in a narrow range of the O2 binding energy (10.0-12.0 kcal/mol)-a useful estimate for computationally screening Au-cluster-based catalysts. We also show that a competitive channel for the OOH desorption exists. Thus, in propylene epoxidation both OOH radicals and H2O2 can attack the active Ti in/on the Au/TS-1 and generate the Ti-OOH sites, which can convert propylene to propylene oxide.

Proceedings of the 15th ACM Great Lakes symposium on VLSI - GLSVSLI '05, 2005

The Journal of Chemical Physics, 2006

We performed density-functional theory analysis of nondissociative CO adsorption on 22 binary Au-... more We performed density-functional theory analysis of nondissociative CO adsorption on 22 binary Au-alloy (Au(n)M(m)) clusters: n=0-3, m=0-3, and m+n=2 (dimers) or 3 (trimers), M=Cu/Ag/Pd/Pt. We report basis-set superposition error corrections to adsorption energies and include both internal energy of adsorption (DeltaU(ads)) and Gibbs free energy of adsorption (DeltaG(ads)) at standard conditions (298.15 K and 1 atm). We found onefold (atop) CO binding on all the clusters except Pd2 (twofold/bridged), Pt2 (twofold/bridged), and Pd3 (threefold). In agreement with the experimental results, we found that CO adsorption is thermodynamically favorable on pure Au/Cu clusters but not on pure Ag clusters and also observed the following adsorption affinity trend: Pd>Pt>Au>Cu>Ag. For alloy dimers we found the following patterns: Au2>M Au>M2 (M=Ag/Cu) and M2>M Au>Au2 (M=Pd/Pt). Alloying Ag/Cu dimers with (more reactive) Au enhanced adsorption and the opposite effect was observed for PdPt dimers. The Ag-Au, Cu-Au, and Pd-Au trimers followed the trends observed on dimers: Au3>M Au2>M2Au>M3 (M=Ag/Cu) and Pd3>Pd2Au>PdAu2>Au3. Interestingly, Pt-Au trimers reacted differently and alloying with Au systematically increased the adsorption affinity: PtAu2>Pt2Au>Pt3>Au3. A strikingly different behavior of Pt is also manifested by the triplet spin state and onefold (atop) binding in Pt3-CO which is in contradiction with the singlet spin state and threefold binding in Pd3-CO. We found a linear correlation between CO binding energy (BE) and elongation of the CO bond. For Ag-Au and Cu-Au clusters, the increase in CO BE (and elongation of the C-O bond which is probably due to the back donation) is accompanied by the decrease in the cluster-CO distance suggesting that the donation (from 5sigma highest occupied molecular orbital in CO to cluster lowest unoccupied molecular orbital) mechanism also contributes to the BE. For Pd-Au clusters, the cluster-CO distance (and CO bond length) increases with increase in the BE, suggesting that the donation mechanism may not be important for those clusters. No clear trend was observed for Pt-Au clusters.

2008 IEEE International Conference on Robotics and Automation, 2008

Page 1. Learning of Moving Cast Shadows for Dynamic Environments Ajay J. Joshi and Nikolaos Papan... more Page 1. Learning of Moving Cast Shadows for Dynamic Environments Ajay J. Joshi and Nikolaos Papanikolopoulos Department of Computer Science and Engineering University of Minnesota-Twin Cities {ajay,npapas}@cs.umn.edu ...

Journal of Catalysis, 2008

2010 20th International Conference on Pattern Recognition, 2010

2010 IEEE International Conference on Robotics and Automation, 2010

The performance of a processor is limited by the specific bottlenecks that a benchmark exposes wh... more The performance of a processor is limited by the specific bottlenecks that a benchmark exposes while running on that processor. Since the quantification of these bottlenecks can be extremely time-consuming, our prior work proposed using the Plackett and Burman design as a statistically-rigorous, but time- efficient method of determining the processor's most significant performance bottlenecks. In this paper, we use

Proceedings of the 2004 international workshop on System level interconnect prediction - SLIP '04, 2004

2006 IEEE International Symposium on Performance Analysis of Systems and Software, 2006

2010 IEEE/IFIP International Conference on Dependable Systems & Networks (DSN), 2010

Abstract Multi-level cell (MLC) NAND flash memories are very popular storage media because of the... more Abstract Multi-level cell (MLC) NAND flash memories are very popular storage media because of their power efficiency and big storage density. This paper proposes to use nonlinear t-error-correcting codes to replace linear BCH codes for error detection and correction in MLC NAND flash memories. Compared to linear BCH codes with the same bit-error correcting capability t, the proposed codes have less errors miscorrected by all codewords and nearly no undetectable errors. For example, the proposed (8281, 8201, 11 ...

Proceedings of the 21st edition of the great lakes symposium on Great lakes symposium on VLSI - GLSVLSI '11, 2011

2009 IEEE Conference on Computer Vision and Pattern Recognition, 2009

19th International Conference on VLSI Design held jointly with 5th International Conference on Embedded Systems Design (VLSID'06), 2006

2005 Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, 2005

Lecture Notes in Computer Science, 2009

The Journal of Physical Chemistry B, 2006

We report a B3LYP density-functional theory (DFT) analysis of O(2) adsorption on 27 Au(n)M(m) (m,... more We report a B3LYP density-functional theory (DFT) analysis of O(2) adsorption on 27 Au(n)M(m) (m, n = 0-3 and m + n = 2 or 3; M = Cu, Ag, Pd, Pt, and Na) clusters. The LANL2DZ pseudopotential and corresponding double-zeta basis set was used for heavy atoms, while a 6-311+G(3df) basis set was used for Na and O. We employed basis-set superposition error (BSSE) corrections in the electronic adsorption energies at 0 K (deltaE(ads)) and also calculated adsorption thermodynamics at standard conditions (298.15 K and 1 atm), i.e., internal energy of adsorption (deltaU(ads)) and Gibbs free energy of adsorption (deltaG(ads)). Natural Bond Orbital (NBO) analysis showed that all the clusters donated electron density to adsorbed O(2) and we successfully predicted intuitive linear correlations between the NBO charge on adsorbed O(2), O-O bond length, and O-O stretching frequency. Although there was no clear trend in the O(2) binding energy (BE = -deltaE(ads)) on pure and alloy dimers, we found the following interesting trend for trimers: BE (MAu(2)) < BE (M(3)) < or = BE (M(2)Au). The alloy trimers containing only one Au atom are most reactive toward O(2) while those with two Au atoms are least reactive. These trends are discussed in the context of the ensemble effect and coulomb interactions. We found an approximate linear correlation between the O(2) BE and charge transfer to O(2) for all 27 clusters. The clusters having strongly electropositive Na atoms (e.g., Na(3) and Na(2)Au) donated almost one full electron to adsorbed O(2), and the BE is maximum on these clusters. Although O(2) dissociation is likely in such cases, we have restricted this study to trends in the adsorption of molecular O(2) only. We also found an approximate linear correlation between the charge transfer and BE versus energy difference between the bare-cluster HOMO and O(2) LUMOs, which we speculate to be a fundamental descriptor of the reactivity of small clusters toward O(2). Part of the scatter in these correlations is attributed to the differences in the O(2) binding orientations on different clusters (geometric effect). Relatively higher bare-cluster HOMO energy eases the charge transfer to adsorbed O(2) and enhances the reactivity toward O(2). The Frontier Orbital Picture (FOP) is not always useful in predicting the most favorable O(2) binding site on clusters. It successfully predicted the cluster-O(2) ground-state configurations for 10 clusters, but failed for the others. Finally, the energetics of fragmentation suggest that the bare and O(2)-covered clusters reported here are stable.

This paper presents the results of a study in which the case study method was used to sort out th... more This paper presents the results of a study in which the case study method was used to sort out the internal and external conditions that might affect the success of a work site trip reduction program. Investigators attempted to disprove a null hypothesis, stated as "The effectiveness of work site trip reduction programs does not depend on organizational culture." The

The Journal of Physical Chemistry B, 2006

Proceedings 2007 IEEE International Conference on Robotics and Automation, 2007

Page 1. Moving Shadow Detection with Low-and Mid-Level Reasoning Ajay J. Joshi, Stefan Atev, Osam... more Page 1. Moving Shadow Detection with Low-and Mid-Level Reasoning Ajay J. Joshi, Stefan Atev, Osama Masoud, and Nikolaos Papanikolopoulos Dept. of Computer Science and Engineering, University of Minnesota – Twin Cities {ajay,atev,masoud,npapas}@cs.umn.edu ...

The Journal of Physical Chemistry B, 2005

We report a detailed density functional theory (B3LYP) analysis of the gas-phase H2O2 formation f... more We report a detailed density functional theory (B3LYP) analysis of the gas-phase H2O2 formation from H2 and O2 on Au3, Au4+, Au5, and Au5-. We find that H2, which interacts only weakly with the Au clusters, is dissociatively added across the Au-O bond, upon interaction with AunO2. One H atom is captured by the adsorbed O2 to form the hydroperoxy intermediate (OOH), while the other H atom is captured by the Au atom. Once formed, the hydroperoxy intermediate acts as a precursor for the closed-loop catalytic cycle. An important common feature of all the pathways is that the rate-determining step of the catalytic cycle is the second H2 addition to form H2O2. The H2O2 desorption is followed by O2 addition to AunH2 to form the hydroperoxy intermediate, thus leading to the closure of the cycle. On the basis of the Gibbs free energy of activation, out of these four clusters, Au4+ is most active for the formation of the H2O2. The 0 K electronic energy of activation and the DeltaGact at the standard conditions are 12.6 and 16.6 kcal/mol respectively. The natural bond orbital charge analysis suggests that the Au clusters remain positively charged (oxidic) in almost all the stages of the cycle. This is interesting in the context of the recent experimental evidence for the activity of cationic Au in CO oxidation and water-gas shift catalysts. We have also found preliminary evidence for a correlation between the activation barrier for the first H2 addition and the O2 binding energy on the Au cluster. It suggests that the minimum activation barrier for the first H2 addition is expected for the Au clusters with 7.0-9.0 kcal/mol O2 binding energy, i.e., in the midrange of the expected interaction energy. This represents a balance between more favorable H2 dissociation when the Aun-O2 interaction is weaker and high O2 coverage when the interaction is stronger. On the basis of this work, we predict that the hydroperoxy intermediate formation can be both thermodynamically and kinetically viable only in a narrow range of the O2 binding energy (10.0-12.0 kcal/mol)-a useful estimate for computationally screening Au-cluster-based catalysts. We also show that a competitive channel for the OOH desorption exists. Thus, in propylene epoxidation both OOH radicals and H2O2 can attack the active Ti in/on the Au/TS-1 and generate the Ti-OOH sites, which can convert propylene to propylene oxide.

Proceedings of the 15th ACM Great Lakes symposium on VLSI - GLSVSLI '05, 2005

The Journal of Chemical Physics, 2006

We performed density-functional theory analysis of nondissociative CO adsorption on 22 binary Au-... more We performed density-functional theory analysis of nondissociative CO adsorption on 22 binary Au-alloy (Au(n)M(m)) clusters: n=0-3, m=0-3, and m+n=2 (dimers) or 3 (trimers), M=Cu/Ag/Pd/Pt. We report basis-set superposition error corrections to adsorption energies and include both internal energy of adsorption (DeltaU(ads)) and Gibbs free energy of adsorption (DeltaG(ads)) at standard conditions (298.15 K and 1 atm). We found onefold (atop) CO binding on all the clusters except Pd2 (twofold/bridged), Pt2 (twofold/bridged), and Pd3 (threefold). In agreement with the experimental results, we found that CO adsorption is thermodynamically favorable on pure Au/Cu clusters but not on pure Ag clusters and also observed the following adsorption affinity trend: Pd>Pt>Au>Cu>Ag. For alloy dimers we found the following patterns: Au2>M Au>M2 (M=Ag/Cu) and M2>M Au>Au2 (M=Pd/Pt). Alloying Ag/Cu dimers with (more reactive) Au enhanced adsorption and the opposite effect was observed for PdPt dimers. The Ag-Au, Cu-Au, and Pd-Au trimers followed the trends observed on dimers: Au3>M Au2>M2Au>M3 (M=Ag/Cu) and Pd3>Pd2Au>PdAu2>Au3. Interestingly, Pt-Au trimers reacted differently and alloying with Au systematically increased the adsorption affinity: PtAu2>Pt2Au>Pt3>Au3. A strikingly different behavior of Pt is also manifested by the triplet spin state and onefold (atop) binding in Pt3-CO which is in contradiction with the singlet spin state and threefold binding in Pd3-CO. We found a linear correlation between CO binding energy (BE) and elongation of the CO bond. For Ag-Au and Cu-Au clusters, the increase in CO BE (and elongation of the C-O bond which is probably due to the back donation) is accompanied by the decrease in the cluster-CO distance suggesting that the donation (from 5sigma highest occupied molecular orbital in CO to cluster lowest unoccupied molecular orbital) mechanism also contributes to the BE. For Pd-Au clusters, the cluster-CO distance (and CO bond length) increases with increase in the BE, suggesting that the donation mechanism may not be important for those clusters. No clear trend was observed for Pt-Au clusters.

2008 IEEE International Conference on Robotics and Automation, 2008

Page 1. Learning of Moving Cast Shadows for Dynamic Environments Ajay J. Joshi and Nikolaos Papan... more Page 1. Learning of Moving Cast Shadows for Dynamic Environments Ajay J. Joshi and Nikolaos Papanikolopoulos Department of Computer Science and Engineering University of Minnesota-Twin Cities {ajay,npapas}@cs.umn.edu ...

Journal of Catalysis, 2008

2010 20th International Conference on Pattern Recognition, 2010

2010 IEEE International Conference on Robotics and Automation, 2010