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Articles 1 - 15 of 15
Full-Text Articles in Engineering
A Fast Three-Step Phase-Shifting Algorithm, Peisen S. Huang, Song Zhang
A Fast Three-Step Phase-Shifting Algorithm, Peisen S. Huang, Song Zhang
Song Zhang
We propose a new three-step phase-shifting algorithm, which is much faster than the traditional three-step algorithm. We achieve the speed advantage by using a simple intensity ratio function to replace the arctangent function in the traditional algorithm. The phase error caused by this new algorithm is compensated for by use of a look-up-table (LUT). Our experimental results show that both the new algorithm and the traditional algorithm generate similar results, but the new algorithm is 3.4 times faster. By implementing this new algorithm in a high-resolution, real-time 3D shape measurement system, we were able to achieve a measurement speed of …
3-D Optical Measurement Using Phase Shifting Based Methods, Peisen S. Huang, Song Zhang
3-D Optical Measurement Using Phase Shifting Based Methods, Peisen S. Huang, Song Zhang
Song Zhang
We review some of our most recent works on 3-D shape measurement using the digital fringe projection and phase-shifting method. First, we introduce the measurement principle and phase-shifting algorithms. Then we discuss an effective method for phase error compensation and a novel idea for system calibration. Finally, we describe a 3-D shape measurement system for high-resolution, real-time 3-D shape acquisition, reconstruction and display.
Systematic, Multisite Short-Range-Order Corrections To The Electronic Structure Of Disordered Alloys From First Principles: The Kkr Nonlocal Cpa From The Dynamical Cluster Approximation, D. A. Biava, Subhradip Ghosh, Duane D. Johnson, W. A. Shelton, Andrei V. Smirnov
Systematic, Multisite Short-Range-Order Corrections To The Electronic Structure Of Disordered Alloys From First Principles: The Kkr Nonlocal Cpa From The Dynamical Cluster Approximation, D. A. Biava, Subhradip Ghosh, Duane D. Johnson, W. A. Shelton, Andrei V. Smirnov
Duane D. Johnson
Although the Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA) is used widely to configurationally average and get electronic structures and energies of disordered alloys, a single-site CPA misses local environment effects, including short-range order (SRO). A proposed nonlocal CPA (NLCPA) recovers translational invariance of the effective medium via k-space coarse graining from the dynamical cluster approximation (DCA), where corrections are systematic as cluster size increases. We implement a first-principles KKR-NLCPA/DCA and show the effects of environment, including SRO, on the electronic structures of fcc CuAu and bcc NiAl.
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang
Song Zhang
This paper describes a novel phase error compensation method for reducing the measurement error caused by non-sinusoidal waveforms in the phase-shifting method. For 3D shape measurement systems using commercial video projectors, the non-sinusoidal nature of the projected fringe patterns as a result of the nonlinear gamma curve of the projectors causes significant phase measurement error and therefore shape measurement error. The proposed phase error compensation method is based on our finding that the phase error due to the non-sinusoidal waveform of the fringe patterns depends only on the nonlinearity of the projector's gamma curve. Therefore, if the projector's gamma curve …
Genetic Programming For Multitimescale Modeling, Kumara Sastry, Duane D. Johnson, David E. Goldberg, Pascal Bellon
Genetic Programming For Multitimescale Modeling, Kumara Sastry, Duane D. Johnson, David E. Goldberg, Pascal Bellon
Duane D. Johnson
A bottleneck for multitimescale thermally activated dynamics is the computation of the potential energy surface. We explore the use of genetic programming (GP) to symbolically regress a mapping of the saddle-point barriers from only a few calculated points via molecular dynamics, thereby avoiding explicit calculation of all barriers. The GP-regressed barrier function enables use of kinetic Monte Carlo to simulate real-time kinetics (seconds to hours) based upon realistic atomic interactions. To illustrate the concept, we apply a GP regression to vacancy-assisted migration on a surface of a concentrated binary alloy (from both quantum and empirical potentials) and predict the diffusion …
Synthesis And Characterization Of Highly Amine Functionalized Mesoporous Organosilicas By An “All-In-One” Approach, Rebecca Voss, Arne Thomas, Markus Antonietti, Geoffrey A. Ozin
Synthesis And Characterization Of Highly Amine Functionalized Mesoporous Organosilicas By An “All-In-One” Approach, Rebecca Voss, Arne Thomas, Markus Antonietti, Geoffrey A. Ozin
Rebecca Cademartiri
Mesoporous organosilicas (MOs) represent a promising class of organic–inorganic nanocomposites for a broad range of applications like catalysis, sensing, separation, or microelectronics. Their distinct feature is the presence of organic groups incorporated into the channel walls of a mesoporous structure. Here, we present a convenient “all-in-one” approach using silsesquioxane surfactant precursors for the functionalization of the channel walls with primary amine groups. The monomer is made by a hydroboration/aminolysis sequence on the base of a commercial monomer, with the template bound to the functionalization site by hydroboration and released after silica condensation and aminolysis. This combination ensures both the placement …
Update On Ethanol Processing Residue Properties, Kurt A. Rosentrater, Kasiviswanathan Muthukumarappan, James Julson, Padmanaban Krishnan
Update On Ethanol Processing Residue Properties, Kurt A. Rosentrater, Kasiviswanathan Muthukumarappan, James Julson, Padmanaban Krishnan
Kurt A. Rosentrater
The production of corn-based ethanol in the U.S. is dramatically increasing, and consequently so is the amount of byproduct materials generated from this processing sector. These coproduct streams are currently solely utilized as livestock feed, which is a route that provides ethanol processors with a substantial revenue source and significantly increases the profitability of the production process. With the construction and operation of many new plants in recent years, these residuals do, however, have much potential for value-added processing and utilization in other sectors as well. This option holds promise of economic benefit for corn processors, especially if the livestock …
Renewable Energy Alternatives: Current Status And Capacities, Kurt A. Rosentrater, Youakim Al-Kalaani
Renewable Energy Alternatives: Current Status And Capacities, Kurt A. Rosentrater, Youakim Al-Kalaani
Kurt A. Rosentrater
A key to the United States’ economic growth is an ever-increasing demand for energy, which has traditionally been met primarily by combusting the hydrocarbons found in fossil fuels. As environmental concerns grow, renewable energy resources are gaining increasing attention. To aid both researchers as well as educators, this paper examines historical energy data for both traditional as well as alternative energy sources. Even with the progressive developments of non-traditional energy sources over the years, the U.S. still receives more than 90% of its energy from fossil and nuclear fuels. Explicit examination of the alternative energy sector has revealed that hydroelectric …
Crossover Energetics For Halogenated Si(100): Vacancy Line Defects, Dimer Vacancy Lines, And Atom Vacancy Lines, G. J. Xu, Nikolai A. Zarkevich, Abhishek Agrawal, A. W. Signore, B. R. Trenhaile, Duane D. Johnson, J. H. Weaver
Crossover Energetics For Halogenated Si(100): Vacancy Line Defects, Dimer Vacancy Lines, And Atom Vacancy Lines, G. J. Xu, Nikolai A. Zarkevich, Abhishek Agrawal, A. W. Signore, B. R. Trenhaile, Duane D. Johnson, J. H. Weaver
Duane D. Johnson
We investigated surface patterning of I-Si(100)-(2×1) both experimentally and theoretically. Using scanning tunneling microscopy, we first examined I destabilization of Si(100)-(2×1) at near saturation. Dimer vacancies formed on the terraces at 600 K, and they grew into lines that were perpendicular to the dimer rows, termed vacancy line defects. These patterns were distinctive from those induced by Cl and Br under similar conditions since the latter formed atom and dimer vacancy lines that were parallel to the dimer rows. Using first-principles density functional theory, we determined the steric repulsive interactions associated with iodine and showed how the observed defect patterns …
Size-Driven Domain Reorientation In Hydrothermally Derived Lead Titanate Nanoparticles, Zhiyuan Ye, Elliot B. Slamovich, Alexander H. King
Size-Driven Domain Reorientation In Hydrothermally Derived Lead Titanate Nanoparticles, Zhiyuan Ye, Elliot B. Slamovich, Alexander H. King
Alexander H. King
High-resolution transmission electron microscopy studies of hydrothermally derived platelike lead titanate nanoparticles reveal that below a critical size of approximately 70 nm, the single ferroelectric domain polarization axis reorients from perpendicular to parallel to the plate. We suggest that during particle growth, ions in the hydrothermal processing medium compensate for the ferroelectric depolarization energy. When the processing medium is removed by washing and drying, single domain nanoparticles minimize their depolarization energy by c-axis flipping.
Importance Of Thermal Disorder On The Properties Of Alloys: Origin Of Paramagnetism And Structural Anomalies In Bcc-Based Fe1−Xalx, Andrei V. Smirnov, W. A. Shelton, Duane D. Johnson
Importance Of Thermal Disorder On The Properties Of Alloys: Origin Of Paramagnetism And Structural Anomalies In Bcc-Based Fe1−Xalx, Andrei V. Smirnov, W. A. Shelton, Duane D. Johnson
Duane D. Johnson
Fe1−xAlx exhibits interesting magnetic and anomalous structural properties as a function of composition and sample processing conditions arising from thermal or off-stoichiometric chemical disorder, and, although well studied, these properties are not understood. In stoichiometric B2 FeAl, including the effects of partial long-range order, i.e., thermal antisites, we find the experimentally observed paramagnetic response with nonzero local moments, in contrast to past investigations that find either a ferromagnetic or nonmagnetic state, both inconsistent with experiment. Moreover, from this magnetochemical coupling, we are able to determine the origins of the observed lattice constant anomalies found in Fe1−xAlx for x≃0.25–0.5 under various …
Mechanism Of Structural Transformation In Bismuth Titanate, Sudhanshu Mallick, Keith J. Bowman, Alexander H. King
Mechanism Of Structural Transformation In Bismuth Titanate, Sudhanshu Mallick, Keith J. Bowman, Alexander H. King
Alexander H. King
Sodium-doped bismuth titanate undergoes a transformation from Bi4Ti3O12 to Na0.5Bi4.5Ti4O15 on heating in air at temperatures exceeding 800 °C. This transformation proceeds through the intermediate Na0.5Bi8.5Ti7O27 structure which is an intergrowth phase of the two. High-resolution transmission electron microscopy was used to study this transformation. From the Moiré pattern that was obtained, the crystallographic orientation of the transformation front has been determined and a mechanism is proposed for this structural transformation.
Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
Prismatic goldnanoparticles in the periodic monolayer arrays prepared with nanosphere lithography technique can be reshaped with femtosecond laser pulses at different powers and wavelengths. As the power density of 400 nm femtosecond laser increases, the prismatic particle tips begin to round and the overall particle shape changes from a prism to a sphere with a tripodal intermediate. The formation of the tip-rounded nanoprisms is probably due to the dewetting properties of gold on quartz surface and the low melting temperature at the tips. The formation of the tripodal nanoparticles is attributed to the inhomogeneous heating and lattice rearrangement of the …
The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays: The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays: The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed
Wenyu Huang
Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the …
Dislocation-Indenter Interaction In Nanoindentation, M. Ravi Shankar, Alexander H. King, Srinivasan Chandrasekar
Dislocation-Indenter Interaction In Nanoindentation, M. Ravi Shankar, Alexander H. King, Srinivasan Chandrasekar
Alexander H. King
A formulation of dislocation-indenter interaction in two-dimensional, isotropic elasticity is presented. A significant dislocation-indenter interaction is predicted when dislocations are nucleated very close to the indenter. This interaction is expected to have an important influence on dislocation motion and multiplication. Upon nucleation close to the indenter, the dislocations are shown to modify the load, load distribution, and moment acting on the indenter. This effect is seen to vary with the indentation contact length. Further away from the indenter, the indenter-dislocation interaction is shown to be negligible.