Robert Sinkovits - Academia.edu (original) (raw)
Uploads
Papers by Robert Sinkovits
Radiation Effects and Defects in Solids, 1991
ABSTRACT Embedded cluster calculations performed on both ground (A2g) and excited (T2g) states of... more ABSTRACT Embedded cluster calculations performed on both ground (A2g) and excited (T2g) states of substitutional Cr in halide elpasolites account successfully for the pressure dependence of photoluminescence spectra.
Journal of Physics and Chemistry of Solids, 1993
& initio embeddedcluster molecular-orbital calculations were performed with the MELD program on b... more & initio embeddedcluster molecular-orbital calculations were performed with the MELD program on both ground (4Ao) and excited (4Tzs) electronic states of substitutional Cr'+ in the halide elpasolites K,NaGaF,, K,NaScF, and Cs,NaYCl,. External interactions of the molecular cluster were represented by pair potentials, and lattice relaxation was accomplished by means of a modification of the HADES lattice-statics program. The calculations account successfully for the pressure dependence of photol~~n~ spectra and of vibration frequencies inferred from their vibronic structure.
Journal of Physics and Chemistry of Solids, 1994
ABSTRACT Radiationless transition rates were predicted ab initio in K2NaScF6:Cr3+ and K2NaGaF6:Cr... more ABSTRACT Radiationless transition rates were predicted ab initio in K2NaScF6:Cr3+ and K2NaGaF6:Cr3+. Embedded cluster calculations provided adiabatic potential energy functions of a1g, eg and t2g nearest-neighbor fluorine displacements in both ground (4A2g.) and excited (4T2g.) states. Transition rates were calculated from normalized lineshape functions G (Ω) derived by evaluating vibrational overlap integrals for an arbitrary combination of linear, quadratic and anharmonic coupling. Predicted transition rates, which are lower than experimental values, were not improved by including anharmonicity.
Journal of Physics and Chemistry of Solids, 1991
Proceedings of the 2014 Annual Conference on Extreme Science and Engineering Discovery Environment - XSEDE '14, 2014
ABSTRACT NSF-funded computing centers have primarily focused on delivering high-performance compu... more ABSTRACT NSF-funded computing centers have primarily focused on delivering high-performance computing resources to academic researchers with the most computationally demanding applications. But now that computational science is so pervasive, there is a need for infrastructure that can serve more researchers and disciplines than just those at the peak of the HPC pyramid. Here we describe SDSC's Comet system, which is scheduled for production in January 2015 and was designed to address the needs of a much larger and more expansive science community-- the "long tail of science". Comet will have a peak performance of 2 petaflop/s, mostly delivered using Intel's next generation Xeon processor. It will include some large-memory and GPU-accelerated nodes, node-local flash memory, 7 PB of Performance Storage, and 6 PB of Durable Storage. These features, together with the availability of high performance virtualization, will enable users to run complex, heterogeneous workloads on a single integrated resource.
Proceedings of the 2015 XSEDE Conference on Scientific Advancements Enabled by Enhanced Cyberinfrastructure - XSEDE '15, 2015
Proceedings of the 2014 Annual Conference on Extreme Science and Engineering Discovery Environment - XSEDE '14, 2014
Proceedings of the Conference on Extreme Science and Engineering Discovery Environment Gateway to Discovery - XSEDE '13, 2013
The goal of this project is to rapidly construct an order-by-order level snapshot of financial ma... more The goal of this project is to rapidly construct an order-by-order level snapshot of financial markets with nanosecond resolution time stamps. We are particularly interested in understanding the impact of highfrequency traders on the security, stability, and fairness of these markets. In this paper, we describe our computational approach, the optimizations that were applied to improve the performance of the software by a factor of more than 125×, and the new capabilities that can be enabled using a combination of fast algorithms and XSEDE resources. 18.3% cancelled in 0.001s 24.2% cancelled in 0.001− 0.05s 31.4% cancelled in 0.05− 1s 26.1% cancelled > 1s Distribution of SPY Quote Life for Orders Cancelled Figure 1. Cancelation rate of S&P 500 Trust (stock symbol SPY). J. GAI ET AL.
Physical Review E, 1996
We present a detailed simulational study of the vertical propagation of weak and strong impulses ... more We present a detailed simulational study of the vertical propagation of weak and strong impulses in deep gravitationally compacted granular columns ͓see R. S. Sinkovits and S. Sen, Phys. Rev. Lett. 74, 2686 ͑1995͔͒.
Physical Review B, 1995
We calculate the interaction of a single helium atom with the low-temperature, orientationally or... more We calculate the interaction of a single helium atom with the low-temperature, orientationally ordered, simple cubic phase of a C60 fullerite crystal using anisotropic, helium-carbon pair potentials. The results of our study predict that helium is readily bound to sites on or near the surface of the fullerite crystal, but that intercalation of helium to the interior of the crystal
Physical Review E, 1999
We present a detailed report [see S. Sen et al., Phys. Rev. Lett. 77, 4855 (1996)] of our numeric... more We present a detailed report [see S. Sen et al., Phys. Rev. Lett. 77, 4855 (1996)] of our numerical and analytical studies on the relaxation of a classical particle in the potentials V(x)= +/-x(2)/2+x(4)/4. Both of the approaches confirm that at all temperatures, the relaxation functions (e.g., velocity relaxation function and position relaxation function) decay asymptotically in time t as sin(omega(0)t)/t. Numerically calculated power spectra of the relaxation functions show a gradual transition with increasing temperature from a single sharp peak located at the harmonic frequency omega(0) to a broad continuous band. The 1/t relaxation is also found when V(x) is a polynomial in powers of x(2) with a nonvanishing coefficient accompanying the x(4) term in V(x). Numerical calculations show that in the cases in which the leading term in V(x) behaves as x(2n) with integer n, the asymptotic relaxation exhibits 1/t(phi) decay where phi =1/(n-1). We briefly discuss the analytical approaches to relaxation studies in these strongly anharmonic systems using direct solution of the equation of motion and using the continued fraction formalism approach for relaxation studies. We show that the study of the dynamics of strongly anharmonic oscillators poses unique difficulties when studied via the continued fraction or any other time-series construction based approaches. We close with comments on the physical processes in which the insights presented in this work may be applicable.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, 2013
Proceedings of the 1st Workshop on Architectures and Systems for Big Data - ASBD '11, 2011
ABSTRACT To meet the growing demand for high performance computing systems that are capable of pr... more ABSTRACT To meet the growing demand for high performance computing systems that are capable of processing large datasets, the San Diego Supercomputer Center is deploying Gordon. This system was specifically designed for data intensive workloads and uses flash memory to fill the large latency gap in the memory hierarchy between DRAM and hard disk. In preparation for the deployment of Gordon, we evaluated the performance of multiple remote storage technologies and file systems for use with the flash memory. We find that OCFS and XFS are both superior to PVFS at delivering fast random access to flash. In addition, our tests indicate that the Linux SCSI target framework (TGT) can export flash storage devices with minimal overhead and achieve a large fraction of the theoretical peak I/O performance. Despite the difficulties in fairly comparing I/O solutions due to the many differences in file systems and service implementations, we conclude that OCFS on TGT is a viable option for our system as it provides both excellent performance and a user-friendly shared file system interface. In those instances where a parallel file system is not required, XFS on TGT is a better alternative.
MRS Proceedings, 1992
... Particle interactions are described by a Lennard-Jones potential of the form V(r) = 4e[(-Ir)1... more ... Particle interactions are described by a Lennard-Jones potential of the form V(r) = 4e[(-Ir)12 _ (g/r)]. (1) ... ACKNOWLEDGEMENTS The authors would like to thank Sam Lambrakos, Sam Trevino and Donald Tsai for their helpful discussions. ...
ABSTRACT Using extensive numerical and some exact asymptotic analyses we argue that the canonical... more ABSTRACT Using extensive numerical and some exact asymptotic analyses we argue that the canonical ensemble relaxation of a classical particle in an anharmonic multiwell potential landscape with leading anharmonicity of form x^2n, n>= 2 leads to asymptotic relaxation of form 1/t^phi to equilibrium, where phi=1\over n-1.footnote S. Sen, R.S. Sinkovits and S. Chakravarti, Physica A (Proc. of Workshop on Dynamics of Complex Systems, Calcutta) in press Consequences of this result to many body relaxation processes in ordered footnote Such as the one in J.A. Krumhansl and J.R. Schrieffer, Phys. Rev. B 11, 3535 (1975) and disordered footnote Such as the one in Y.H. Hwang and X-l. Wu, Phys. Rev. Lett. 74, 2284 (1995) systems will be discussed.
Radiation Effects and Defects in Solids, 1991
ABSTRACT Embedded cluster calculations performed on both ground (A2g) and excited (T2g) states of... more ABSTRACT Embedded cluster calculations performed on both ground (A2g) and excited (T2g) states of substitutional Cr in halide elpasolites account successfully for the pressure dependence of photoluminescence spectra.
Journal of Physics and Chemistry of Solids, 1993
& initio embeddedcluster molecular-orbital calculations were performed with the MELD program on b... more & initio embeddedcluster molecular-orbital calculations were performed with the MELD program on both ground (4Ao) and excited (4Tzs) electronic states of substitutional Cr'+ in the halide elpasolites K,NaGaF,, K,NaScF, and Cs,NaYCl,. External interactions of the molecular cluster were represented by pair potentials, and lattice relaxation was accomplished by means of a modification of the HADES lattice-statics program. The calculations account successfully for the pressure dependence of photol~~n~ spectra and of vibration frequencies inferred from their vibronic structure.
Journal of Physics and Chemistry of Solids, 1994
ABSTRACT Radiationless transition rates were predicted ab initio in K2NaScF6:Cr3+ and K2NaGaF6:Cr... more ABSTRACT Radiationless transition rates were predicted ab initio in K2NaScF6:Cr3+ and K2NaGaF6:Cr3+. Embedded cluster calculations provided adiabatic potential energy functions of a1g, eg and t2g nearest-neighbor fluorine displacements in both ground (4A2g.) and excited (4T2g.) states. Transition rates were calculated from normalized lineshape functions G (Ω) derived by evaluating vibrational overlap integrals for an arbitrary combination of linear, quadratic and anharmonic coupling. Predicted transition rates, which are lower than experimental values, were not improved by including anharmonicity.
Journal of Physics and Chemistry of Solids, 1991
Proceedings of the 2014 Annual Conference on Extreme Science and Engineering Discovery Environment - XSEDE '14, 2014
ABSTRACT NSF-funded computing centers have primarily focused on delivering high-performance compu... more ABSTRACT NSF-funded computing centers have primarily focused on delivering high-performance computing resources to academic researchers with the most computationally demanding applications. But now that computational science is so pervasive, there is a need for infrastructure that can serve more researchers and disciplines than just those at the peak of the HPC pyramid. Here we describe SDSC's Comet system, which is scheduled for production in January 2015 and was designed to address the needs of a much larger and more expansive science community-- the "long tail of science". Comet will have a peak performance of 2 petaflop/s, mostly delivered using Intel's next generation Xeon processor. It will include some large-memory and GPU-accelerated nodes, node-local flash memory, 7 PB of Performance Storage, and 6 PB of Durable Storage. These features, together with the availability of high performance virtualization, will enable users to run complex, heterogeneous workloads on a single integrated resource.
Proceedings of the 2015 XSEDE Conference on Scientific Advancements Enabled by Enhanced Cyberinfrastructure - XSEDE '15, 2015
Proceedings of the 2014 Annual Conference on Extreme Science and Engineering Discovery Environment - XSEDE '14, 2014
Proceedings of the Conference on Extreme Science and Engineering Discovery Environment Gateway to Discovery - XSEDE '13, 2013
The goal of this project is to rapidly construct an order-by-order level snapshot of financial ma... more The goal of this project is to rapidly construct an order-by-order level snapshot of financial markets with nanosecond resolution time stamps. We are particularly interested in understanding the impact of highfrequency traders on the security, stability, and fairness of these markets. In this paper, we describe our computational approach, the optimizations that were applied to improve the performance of the software by a factor of more than 125×, and the new capabilities that can be enabled using a combination of fast algorithms and XSEDE resources. 18.3% cancelled in 0.001s 24.2% cancelled in 0.001− 0.05s 31.4% cancelled in 0.05− 1s 26.1% cancelled > 1s Distribution of SPY Quote Life for Orders Cancelled Figure 1. Cancelation rate of S&P 500 Trust (stock symbol SPY). J. GAI ET AL.
Physical Review E, 1996
We present a detailed simulational study of the vertical propagation of weak and strong impulses ... more We present a detailed simulational study of the vertical propagation of weak and strong impulses in deep gravitationally compacted granular columns ͓see R. S. Sinkovits and S. Sen, Phys. Rev. Lett. 74, 2686 ͑1995͔͒.
Physical Review B, 1995
We calculate the interaction of a single helium atom with the low-temperature, orientationally or... more We calculate the interaction of a single helium atom with the low-temperature, orientationally ordered, simple cubic phase of a C60 fullerite crystal using anisotropic, helium-carbon pair potentials. The results of our study predict that helium is readily bound to sites on or near the surface of the fullerite crystal, but that intercalation of helium to the interior of the crystal
Physical Review E, 1999
We present a detailed report [see S. Sen et al., Phys. Rev. Lett. 77, 4855 (1996)] of our numeric... more We present a detailed report [see S. Sen et al., Phys. Rev. Lett. 77, 4855 (1996)] of our numerical and analytical studies on the relaxation of a classical particle in the potentials V(x)= +/-x(2)/2+x(4)/4. Both of the approaches confirm that at all temperatures, the relaxation functions (e.g., velocity relaxation function and position relaxation function) decay asymptotically in time t as sin(omega(0)t)/t. Numerically calculated power spectra of the relaxation functions show a gradual transition with increasing temperature from a single sharp peak located at the harmonic frequency omega(0) to a broad continuous band. The 1/t relaxation is also found when V(x) is a polynomial in powers of x(2) with a nonvanishing coefficient accompanying the x(4) term in V(x). Numerical calculations show that in the cases in which the leading term in V(x) behaves as x(2n) with integer n, the asymptotic relaxation exhibits 1/t(phi) decay where phi =1/(n-1). We briefly discuss the analytical approaches to relaxation studies in these strongly anharmonic systems using direct solution of the equation of motion and using the continued fraction formalism approach for relaxation studies. We show that the study of the dynamics of strongly anharmonic oscillators poses unique difficulties when studied via the continued fraction or any other time-series construction based approaches. We close with comments on the physical processes in which the insights presented in this work may be applicable.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, 2013
Proceedings of the 1st Workshop on Architectures and Systems for Big Data - ASBD '11, 2011
ABSTRACT To meet the growing demand for high performance computing systems that are capable of pr... more ABSTRACT To meet the growing demand for high performance computing systems that are capable of processing large datasets, the San Diego Supercomputer Center is deploying Gordon. This system was specifically designed for data intensive workloads and uses flash memory to fill the large latency gap in the memory hierarchy between DRAM and hard disk. In preparation for the deployment of Gordon, we evaluated the performance of multiple remote storage technologies and file systems for use with the flash memory. We find that OCFS and XFS are both superior to PVFS at delivering fast random access to flash. In addition, our tests indicate that the Linux SCSI target framework (TGT) can export flash storage devices with minimal overhead and achieve a large fraction of the theoretical peak I/O performance. Despite the difficulties in fairly comparing I/O solutions due to the many differences in file systems and service implementations, we conclude that OCFS on TGT is a viable option for our system as it provides both excellent performance and a user-friendly shared file system interface. In those instances where a parallel file system is not required, XFS on TGT is a better alternative.
MRS Proceedings, 1992
... Particle interactions are described by a Lennard-Jones potential of the form V(r) = 4e[(-Ir)1... more ... Particle interactions are described by a Lennard-Jones potential of the form V(r) = 4e[(-Ir)12 _ (g/r)]. (1) ... ACKNOWLEDGEMENTS The authors would like to thank Sam Lambrakos, Sam Trevino and Donald Tsai for their helpful discussions. ...
ABSTRACT Using extensive numerical and some exact asymptotic analyses we argue that the canonical... more ABSTRACT Using extensive numerical and some exact asymptotic analyses we argue that the canonical ensemble relaxation of a classical particle in an anharmonic multiwell potential landscape with leading anharmonicity of form x^2n, n>= 2 leads to asymptotic relaxation of form 1/t^phi to equilibrium, where phi=1\over n-1.footnote S. Sen, R.S. Sinkovits and S. Chakravarti, Physica A (Proc. of Workshop on Dynamics of Complex Systems, Calcutta) in press Consequences of this result to many body relaxation processes in ordered footnote Such as the one in J.A. Krumhansl and J.R. Schrieffer, Phys. Rev. B 11, 3535 (1975) and disordered footnote Such as the one in Y.H. Hwang and X-l. Wu, Phys. Rev. Lett. 74, 2284 (1995) systems will be discussed.