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Articles 1 - 10 of 10
Full-Text Articles in Physics
Air Shower Simulation Using Geant4 And Commodity Parallel Computing, L. Anchordoqui, G. Cooperman, V. Grinberg, T. Mccauley, T. Paul, S. Reucroft, J. Swain, G. Alverson
Air Shower Simulation Using Geant4 And Commodity Parallel Computing, L. Anchordoqui, G. Cooperman, V. Grinberg, T. Mccauley, T. Paul, S. Reucroft, J. Swain, G. Alverson
Gene D. Cooperman
We present an evaluation of a simulated cosmic ray shower, based on GEANT4 and TOP-C, which tracks all the particles in the shower. TOP-C (Task Oriented Parallel C) provides a framework for parallel algorithm development which makes tractable the problem of following each particle. This method is compared with a simulation program which employs the Hillas thinning algorithm.
Frequency Dependence In The Initiation Of Laser-Induced Damage, Jeremy Gulley
Frequency Dependence In The Initiation Of Laser-Induced Damage, Jeremy Gulley
Jeremy R. Gulley
Numerous studies have investigated the role of photoionization in ultrafast laser-induced damage of bulk dielectrics. This study examines the role of spectral width and instantaneous laser frequency in laser-induced damage using a frequency dependent multiphoton ionization model and numerical simulation of an 800 nm laser pulse propagating through fused silica. When the individual photon wavelengths are greater than 827 nm, an additional photon is required for photoionization, reducing the probability of the event by many orders of magnitude. Simulation results suggest that this frequency dependence may significantly affect the processes of laser-induced damage and filamentation.
Improving Thermoelectric Properties Of Chemically Synthesized Bi2te3-Based Nanocrystals By Annealing, Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda
Improving Thermoelectric Properties Of Chemically Synthesized Bi2te3-Based Nanocrystals By Annealing, Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda
Jeffrey Dyck
The power factors of chemically synthesized Bi2Te3 and Bi0.5Sb1.5Te3 nanocrystals (NCs) were improved up to 2.4 and 7.8 μW cm−1 K−2, respectively, which are significantly higher than previously reported values for chemically synthesized Bi2Te3 NCs and even comparable to the recently reported highest power factor of 5 μW cm−1 K−2 for Bi2Te3 NCs consolidated by spark plasma sintering. This improvement was achieved by annealing the NCs under argon protection, and the crystal structures and morphologies of these annealed NCs were characterized via XRD, SEM, and TEM measurements. The temperature-dependent thermoelectric properties of these modified NCs were explored on cold-pressed pellets …
Enhancing Thermoelectric Performance Of Ternary Nanocrystals Through Adjusting Carrier Concentration., Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda
Enhancing Thermoelectric Performance Of Ternary Nanocrystals Through Adjusting Carrier Concentration., Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda
Jeffrey Dyck
The carrier concentration of chemically synthesized Bi2Te3-based nanocrystals (NCs) is for the first time reported to be adjusted by forming ternary Bi2−xSbxTe3 NCs (x = 0.02, 0.05, 0.10, 0.20, 0.50, and 1.50) through partial substitution of Bi with Sb. Carrier concentrations of ternary Bi2−xSbxTe3 NCs were successfully adjusted by a factor of more than 10 controlled by the stoichiometric partial Sb/Bi substitution level. The power factors of the stoichiometric ternary Bi2−xSbxTe3 NCs improved three times compared to the parent Bi2Te3 due to the carrier concentration adjustment.
Ultrashort-Pulse Propagation Through Free-Carrier Plasmas, Jeremy Gulley, William Dennis
Ultrashort-Pulse Propagation Through Free-Carrier Plasmas, Jeremy Gulley, William Dennis
Jeremy R. Gulley
The past decade has seen frequent use of a modified nonlinear Schrödinger equation to describe ultrashort pulse propagation in materials where free-carrier plasmas are present. The optical contribution from the resulting free-current densities in this equation is often described using a classical Drude model. However, the ultimate form of this contribution in the modified nonlinear Schrödinger equation is somewhat inconsistent in the literature. We clarify this ambiguity by deriving the modified nonlinear Schrödinger equation from the classical wave equation containing a free-current density contribution. The Drude model is then used to obtain an expression for the complex free-carrier current density …
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Nancy A. Burnham
It has long been recognized that the angular deflection of an atomic force microscope(AFM) cantilever under “normal” loading conditions can be profoundly influenced by the friction between the tip and the surface. It is shown here that a remarkably quantifiable hysteresis occurs in the slope of loading curves whenever the normal flexural stiffness of the AFM cantilever is greater than that of the sample. This situation arises naturally in cantilever-on-cantilever calibration, but also when trying to measure the stiffness of nanomechanical devices or test structures, or when probing any type of surface or structure that is much more compliant along …
Transport Studies Of Nh4no3 Doped Methyl Cellulose Electrolyte, Siti Rohana Majid, Shuhaimi N. E. A., Teo L. P., Arof A. K.
Transport Studies Of Nh4no3 Doped Methyl Cellulose Electrolyte, Siti Rohana Majid, Shuhaimi N. E. A., Teo L. P., Arof A. K.
Siti Rohana Majid
This work reports on the transport properties of NH4NO3 doped methyl cellulose (MC) polymer electrolyte. The polymer electrolyte films were prepared by the technique of solvent casting. The highest room temperature conductivity of MC doped with 25 wt.% NH4NO3 is 2.10 +/- 0.37 x 10(-6) S cm(-1). Conductivity-temperature relationship obeys the Vogel-Tamman-Fulcher (VTF) rule from which the glass transition temperature, T-g was evaluated. The mobility, p and number density of charge carrier, n were calculated using the Rice and Roth model. (C) 2010 Elsevier B.V. All rights reserved.
Characteristics Of Methyl Cellulose-Nh4no3-Peg Electrolyte And Application In Fuel Cells, Siti Rohana Majid, Shuhaimi N. E. A., Alias N. A., Kufian M. Z., Arof A. K.
Characteristics Of Methyl Cellulose-Nh4no3-Peg Electrolyte And Application In Fuel Cells, Siti Rohana Majid, Shuhaimi N. E. A., Alias N. A., Kufian M. Z., Arof A. K.
Siti Rohana Majid
We report the viability of methyl cellulose (MC) as a membrane in a polymer electrolyte membrane fuel cell (PEMFC). Methyl cellulose serves as the polymer host, ammonium nitrate (NH4NO3) as the doping salt and poly(ethylene glycol) (PEG) as plasticizer. Conductivity measurement was carried out using electrochemical impedance spectroscopy. The room temperature conductivity of pure MC film is is (3.08 +/- 0.63) x 10(-11)S cm(-1). The conductivity increased to (2.10 +/- 0.37) x 10(-6)S cm(-1) on addition of 25 wt.% NH4NO3. By adding 15 wt.% of PEG 200 to the highest conducting sample in the MC-NH4NO3 system, the conductivity was further …
Evolution Of Solitary Waves For A Perturbed Nonlinear Schrodinger Equation, Tim Marchant
Evolution Of Solitary Waves For A Perturbed Nonlinear Schrodinger Equation, Tim Marchant
Tim Marchant
Soliton perturbation theory is used to determine the evolution of a solitary wave described by a perturbed nonlinear Schrödinger equation. Perturbation terms, which model wide classes of physically relevant perturbations, are considered. An analytical solution is found for the first-order correction of the evolving solitary wave. This solution for the solitary wave tail is in integral form and an explicit expression is found, for large time. Singularity theory, usually used for combustion problems, is applied to the large time expression for the solitary wave tail. Analytical results are obtained, such as the parameter regions in which qualitatively different types of …
Understanding Space Weather Customers In Gps-Reliant Industries, Jennifer Meehan, G. Fisher, W. Murtagh
Understanding Space Weather Customers In Gps-Reliant Industries, Jennifer Meehan, G. Fisher, W. Murtagh
Jennifer (Jinni) Meehan
No abstract provided.