Kevin Bowers - Academia.edu (original) (raw)

Papers by Kevin Bowers

Proceedings of the 2023 ACM/SIGDA International Symposium on Field Programmable Gate Arrays

A system for automatically identifying the script used in a handwritten document image is describ... more A system for automatically identifying the script used in a handwritten document image is described. The system was developed using a 496-document dataset representing six scripts, eight languages, and 281 writers. Documents were characterized by the mean, standard deviation, and skew of five connected component features. A linear discriminant analysis was used to classify new documents, and tested using writer-sensitive cross-validation. Classification accuracy averaged 88% across the six scripts. The same method, applied within the Roman subcorpus, discriminated English and German documents with 85% accuracy. Keywords: script, language, handwriting, discrimination, features 1. Introduction Script and language identification are important parts of the automatic processing of document images in an international environment. A document's script (e.g., Cyrillic or Roman) must be known in order to choose an appropriate optical character recognition (OCR) algorithm. For scripts use...

Three-dimensional fully kinetic Particle-in-Cell plasma simulations are used to study the magneti... more Three-dimensional fully kinetic Particle-in-Cell plasma simulations are used to study the magnetic reconnection in an initially force-free plasma with a sheet pinch configuration. The configuration drives unstable collisionless tearing modes at multiple resonant surfaces. The nonlinear ...

A system for automatically identifying the script used in a handwritten document image is describ... more A system for automatically identifying the script used in a handwritten document image is described. The system was developed using a 496-document dataset representing six scripts, eight languages, and 281 writers. Documents were characterized by the mean, standard deviation, and skew of five connected component features. A linear discriminant analysis was used to classify new documents, and tested using writer-sensitive cross-validation. Classification accuracy averaged 88% across the six scripts. The same method, applied within the Roman subcorpus, discriminated English and German documents with 85% accuracy. Pilot results indicate that a variation of the method may be applicable to writer identification. 1. Introduction Script and language identification are important parts of the automatic processing of document images in an international environment. A document's script (e.g., Cyrillic or Roman) must be known in order to choose an appropriate optical character recognition ...

New Journal of Physics, 2013

Experimental data on laser-driven carbon C 6+ ion acceleration with a peak intensity of 5 × 10 20... more Experimental data on laser-driven carbon C 6+ ion acceleration with a peak intensity of 5 × 10 20 W cm −2 are presented and compared for opaque target normal sheath acceleration (TNSA) and relativistically transparent laser-plasma interactions. Particle numbers, peak ion energy and conversion efficiency have been investigated for target thicknesses from 50 nm to 25 µm using unprecedented full spectral beam profile line-out measurements made using a novel high-resolution ion wide-angle spectrometer. For thicknesses of about 200 nm, particle numbers and peak energy increase to 5 × 10 11 carbon C 6+ particles between 33 and 700 MeV (60 MeV u −1), which is a factor of five higher in particle number than that observed for targets with micron thickness. For 200 nm thick targets, we find that the peak conversion efficiency is 6% and that up to 55% of the target under the laser focal spot is accelerated to energies above 33 MeV. This contrasts with the results for targets with micron thickness, where surface acceleration with TNSA is dominant. The experimental findings are consistent with two-dimensional particle-in-cell simulations.

The Journal of Chemical Physics, 2007

… , Proceedings of the …, 2007

Page 1. Although molecular dynamics (MD) simulations of biomolecular systems often run for days t... more Page 1. Although molecular dynamics (MD) simulations of biomolecular systems often run for days to months, many events of great scientific interest and pharmaceutical relevance occur on long time scales that remain beyond reach. ...

Fully electromagnetic particle in cell simulations of nonlinear waves propagation and interaction... more Fully electromagnetic particle in cell simulations of nonlinear waves propagation and interaction is performed in two-dimensional plane geometry in magnetized plasma in ion cyclotron frequency range. A spectrum of fast wave modes with different total energies with wave numbers parallel and perpendicular to uniform equilibrium magnetic field is launched into plasma and the nonlinear dynamics of these waves is analyzed.

Physical review letters, Jan 22, 2011

Breakout afterburner (BOA) laser-ion acceleration has been demonstrated for the first time in the... more Breakout afterburner (BOA) laser-ion acceleration has been demonstrated for the first time in the laboratory. In the BOA, an initially solid-density target undergoes relativistically induced transparency, initiating a period of enhanced ion acceleration. First-ever kinetic simulations of the BOA in three dimensions show that the ion beam forms lobes in the direction orthogonal to laser polarization and propagation. Analytic theory presented for the electron dynamics in the laser ponderomotive field explains how azimuthal symmetry breaks even for a symmetric laser intensity profile; these results are consistent with recent experiments at the Trident laser facility.

To support the design and analysis of x-ray radiographic facilities and experiments at Los Alamos... more To support the design and analysis of x-ray radiographic facilities and experiments at Los Alamos, we have developed an integrated chain model, which is a set of linked physics simulation codes to generate self-consistent synthetic radiographs of experiments (1). The expectation-maximization (EM) algorithm (2) has recently been used to great advantage to link particle- in-cell (PIC) methods, which model electron

International Journal on Document Analysis and Recognition, 1999

Physical Review Letters, 2006

Physical Review Letters, 2009

Physical Review Letters, 2008

Proceedings of the 2023 ACM/SIGDA International Symposium on Field Programmable Gate Arrays

A system for automatically identifying the script used in a handwritten document image is describ... more A system for automatically identifying the script used in a handwritten document image is described. The system was developed using a 496-document dataset representing six scripts, eight languages, and 281 writers. Documents were characterized by the mean, standard deviation, and skew of five connected component features. A linear discriminant analysis was used to classify new documents, and tested using writer-sensitive cross-validation. Classification accuracy averaged 88% across the six scripts. The same method, applied within the Roman subcorpus, discriminated English and German documents with 85% accuracy. Keywords: script, language, handwriting, discrimination, features 1. Introduction Script and language identification are important parts of the automatic processing of document images in an international environment. A document's script (e.g., Cyrillic or Roman) must be known in order to choose an appropriate optical character recognition (OCR) algorithm. For scripts use...

Three-dimensional fully kinetic Particle-in-Cell plasma simulations are used to study the magneti... more Three-dimensional fully kinetic Particle-in-Cell plasma simulations are used to study the magnetic reconnection in an initially force-free plasma with a sheet pinch configuration. The configuration drives unstable collisionless tearing modes at multiple resonant surfaces. The nonlinear ...

A system for automatically identifying the script used in a handwritten document image is describ... more A system for automatically identifying the script used in a handwritten document image is described. The system was developed using a 496-document dataset representing six scripts, eight languages, and 281 writers. Documents were characterized by the mean, standard deviation, and skew of five connected component features. A linear discriminant analysis was used to classify new documents, and tested using writer-sensitive cross-validation. Classification accuracy averaged 88% across the six scripts. The same method, applied within the Roman subcorpus, discriminated English and German documents with 85% accuracy. Pilot results indicate that a variation of the method may be applicable to writer identification. 1. Introduction Script and language identification are important parts of the automatic processing of document images in an international environment. A document's script (e.g., Cyrillic or Roman) must be known in order to choose an appropriate optical character recognition ...

New Journal of Physics, 2013

Experimental data on laser-driven carbon C 6+ ion acceleration with a peak intensity of 5 × 10 20... more Experimental data on laser-driven carbon C 6+ ion acceleration with a peak intensity of 5 × 10 20 W cm −2 are presented and compared for opaque target normal sheath acceleration (TNSA) and relativistically transparent laser-plasma interactions. Particle numbers, peak ion energy and conversion efficiency have been investigated for target thicknesses from 50 nm to 25 µm using unprecedented full spectral beam profile line-out measurements made using a novel high-resolution ion wide-angle spectrometer. For thicknesses of about 200 nm, particle numbers and peak energy increase to 5 × 10 11 carbon C 6+ particles between 33 and 700 MeV (60 MeV u −1), which is a factor of five higher in particle number than that observed for targets with micron thickness. For 200 nm thick targets, we find that the peak conversion efficiency is 6% and that up to 55% of the target under the laser focal spot is accelerated to energies above 33 MeV. This contrasts with the results for targets with micron thickness, where surface acceleration with TNSA is dominant. The experimental findings are consistent with two-dimensional particle-in-cell simulations.

The Journal of Chemical Physics, 2007

… , Proceedings of the …, 2007

Page 1. Although molecular dynamics (MD) simulations of biomolecular systems often run for days t... more Page 1. Although molecular dynamics (MD) simulations of biomolecular systems often run for days to months, many events of great scientific interest and pharmaceutical relevance occur on long time scales that remain beyond reach. ...

Fully electromagnetic particle in cell simulations of nonlinear waves propagation and interaction... more Fully electromagnetic particle in cell simulations of nonlinear waves propagation and interaction is performed in two-dimensional plane geometry in magnetized plasma in ion cyclotron frequency range. A spectrum of fast wave modes with different total energies with wave numbers parallel and perpendicular to uniform equilibrium magnetic field is launched into plasma and the nonlinear dynamics of these waves is analyzed.

Physical review letters, Jan 22, 2011

Breakout afterburner (BOA) laser-ion acceleration has been demonstrated for the first time in the... more Breakout afterburner (BOA) laser-ion acceleration has been demonstrated for the first time in the laboratory. In the BOA, an initially solid-density target undergoes relativistically induced transparency, initiating a period of enhanced ion acceleration. First-ever kinetic simulations of the BOA in three dimensions show that the ion beam forms lobes in the direction orthogonal to laser polarization and propagation. Analytic theory presented for the electron dynamics in the laser ponderomotive field explains how azimuthal symmetry breaks even for a symmetric laser intensity profile; these results are consistent with recent experiments at the Trident laser facility.

To support the design and analysis of x-ray radiographic facilities and experiments at Los Alamos... more To support the design and analysis of x-ray radiographic facilities and experiments at Los Alamos, we have developed an integrated chain model, which is a set of linked physics simulation codes to generate self-consistent synthetic radiographs of experiments (1). The expectation-maximization (EM) algorithm (2) has recently been used to great advantage to link particle- in-cell (PIC) methods, which model electron

International Journal on Document Analysis and Recognition, 1999

Physical Review Letters, 2006

Physical Review Letters, 2009

Physical Review Letters, 2008