Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- CCD cameras -- Calibration (2)
- Image processing -- Digital techniques (2)
- Methane -- Environmental aspects (2)
- Achromatism (1)
- Air -- Pollution (1)
-
- Boundary value problems (1)
- Buffer solutions (1)
- Cadmium compounds (1)
- Charge coupled devices (1)
- Climatic changes (1)
- Complementary metal oxide semiconductors (1)
- Condensed matter (1)
- Crops and climate (1)
- Crystals -- Identification (1)
- Electromagnetic theory -- Mathematics (1)
- Electron microscopy (1)
- Electron transport (1)
- Electrons -- Emission -- Measurement (1)
- Electrostatics -- Study and teaching (1)
- Enthalpy (1)
- Environmental conditions (1)
- Fluid dynamics (1)
- Fluid mechanics (1)
- Green’s functions (1)
- Laminar flow (1)
- Laplacian operator (1)
- Mathematics -- Study and teaching -- Research (1)
- Methane -- Measurement (1)
- Multiphase flow -- Mathematical models (1)
- Nanostructured materials (1)
Articles 1 - 16 of 16
Full-Text Articles in Physics
General Validity Of Reciprocity In Quantum Mechanics, P.T. Leung, H. Y. Xie, D. P. Tsai
General Validity Of Reciprocity In Quantum Mechanics, P.T. Leung, H. Y. Xie, D. P. Tsai
Physics Faculty Publications and Presentations
The concept of reciprocity symmetry for matter-wave propagation is established for nonrelativistic quantum mechanics with previous results in the literature extended to include nonlocal interactions. Examples are given for cases with both local and nonlocal potentials, where we show in particular that reciprocity can be violated for the motion of a charged particle in an external electromagnetic field. In addition, this symmetry is applied to interpret a recent analysis [Phys. Rev. A 64, 042716 (2001)] on the symmetry of transmission through one-dimensional complex potentials, with the emphasis that the validity of reciprocity can go beyond that of time-reversal symmetry, such …
A Better Nondimensionalization Scheme For Slender Laminar Flows: The Laplacian Operator Scaling Method, Mark M. Weislogel, Yongkang Chen, D. Bolleddula
A Better Nondimensionalization Scheme For Slender Laminar Flows: The Laplacian Operator Scaling Method, Mark M. Weislogel, Yongkang Chen, D. Bolleddula
Mechanical and Materials Engineering Faculty Publications and Presentations
A scaling of the two-dimensional Laplacian operator is demonstrated for certain solutions (at least) to Poisson’s equation. It succeeds by treating the operator as a single geometric scale entity. The belated and rather subtle method provides an efficient assessment of the geometrical dependence of the problem and is preferred when practicable to the hydraulic diameter or term-by-term scaling for slender fully developed laminar flows. The improved accuracy further reduces the reliance of problems on widely varying numerical data or cumbersome theoretical forms and improves the prospects of exact or approximate theoretical analysis. Simple example problems are briefly described that demonstrate …
Green Dyadic For The Proca Fields, P.T. Leung, Paul Dragulin
Green Dyadic For The Proca Fields, P.T. Leung, Paul Dragulin
Physics Faculty Publications and Presentations
The dyadic Green functions for the Proca fields in free space are derived to include singular terms. Both the electric and magnetic types will be obtained with the results reduced back to those for the Maxwell fields in the limit of zero photon mass. Moreover, the singular terms are identical in both massless and massive electrodynamics. As an illustration, the results are applied to obtain the exact dynamical fields for an oscillating dipole which reduce back to the well-known expressions for static fields derived previously in the literature for massive electrodynamics.
Spatial Variability Of Methane Emissions From Rice Fields And Implications For Experimental Design, M. A. K. Khalil, Christopher Lee Butenhoff
Spatial Variability Of Methane Emissions From Rice Fields And Implications For Experimental Design, M. A. K. Khalil, Christopher Lee Butenhoff
Physics Faculty Publications and Presentations
It is observed that side by side plots in rice fields, managed by the same practices, produce methane emissions that are often different by factors of 2 to 4. Similarly on a given day when many plots are sampled, the emissions from one plot may differ from another by factors of 3-4 on average. These large variations must be taken into account if these data are extrapolated to larger scales such as countries or the world. In this paper we analyze and delineate the nature of this variability. We distinguish temporal and spatial variability and examine the effects of both …
Image Properties In An Aberration-Corrected Photoemission Electron Microscope, Rolf Könenkamp, T. Jones, J. Elstner, Robert Campbell Word, Gertrude Rempfer, Todd Dixon, Luis Almaraz, Walter P. Skoczylas
Image Properties In An Aberration-Corrected Photoemission Electron Microscope, Rolf Könenkamp, T. Jones, J. Elstner, Robert Campbell Word, Gertrude Rempfer, Todd Dixon, Luis Almaraz, Walter P. Skoczylas
Physics Faculty Publications and Presentations
We report recent progress in the construction of a new aberration-corrected photoemission electron microscope. The correcting element in this instrument is a hyperbolic electron mirror which corrects for chromatic and spherical aberration. We present first images obtained with the new instrument and numerical results from trajectory and wave-optical calculations indicating that the resolution can be of the order of 1 nm.
Production, Oxidation, And Emissions Of Methane From Rice Fields In China, M. A. K. Khalil, Martha J. Shearer, R. A. Rasmussen, Chang-Lin Duan, Lixin Ren
Production, Oxidation, And Emissions Of Methane From Rice Fields In China, M. A. K. Khalil, Martha J. Shearer, R. A. Rasmussen, Chang-Lin Duan, Lixin Ren
Physics Faculty Publications and Presentations
Detailed field studies of methane emissions from rice fields show that when nitrogen fertilizers are used with intermittent irrigation the seasonal average flux is about 3 mg/m²/hr. When continuous flooding and organic material is added to the same fields, the emissions rise to nearly 30 mg/m²/hr. Production rates measured during the two years when both organic material and water were applied to these fields were found to be 60 and 90 mg/m²/hr in consecutive years. The fraction oxidized is calculated to be about 80% one year and 43% the next year. The results suggest that high organic fertilizer increases production, …
Creation Of Nanopatterns By Local Protonation Of P4vp Via Dip Pen Nanolithography, Carsten Maedler, S. Chada, Xiquan Cui, M. Taylor, Mingdi Yan, Andres H. La Rosa
Creation Of Nanopatterns By Local Protonation Of P4vp Via Dip Pen Nanolithography, Carsten Maedler, S. Chada, Xiquan Cui, M. Taylor, Mingdi Yan, Andres H. La Rosa
Physics Faculty Publications and Presentations
The elastic mechanical response of a poly(4-vinylpyridine) film is exploited to create nanostructures under ambient conditions via dip pen nanolithography. Using a pH 4 phosphate buffer solution as the "ink," a series of experimental results indicates that the nanometer-sized structures are due to local swelling of the film’s pyridyl groups upon their protonation with the hydronium ions delivered by the tip. Control over the structures’ height is gained by properly selecting the writing velocities or the dwell time, respectively.
Dynamical Evolution Of Volume Fractions In Multipressure Multiphase Flow Models, C. H. Chang, John D. Ramshaw
Dynamical Evolution Of Volume Fractions In Multipressure Multiphase Flow Models, C. H. Chang, John D. Ramshaw
Physics Faculty Publications and Presentations
Compared to single-pressure models, multipressure multiphase flow models require additional closure relations to determine the individual pressures of the different phases. These relations are often taken to be evolution equations for the volume fractions. We present a rigorous theoretical framework for constructing such equations for compressible multiphase mixtures in terms of submodels for the relative volumetric expansion rates ∆Ei of the phases. These quantities are essentially the rates at which the phases dynamically expand or contract in response to pressure differences, and represent the general tendency of the volume fractions to relax toward values that produce local pressure equilibrium. We …
How Students Use Mathematical Resources In An Electrostatics Context, Dawn C. Meredith, Karen A. Marrongelle
How Students Use Mathematical Resources In An Electrostatics Context, Dawn C. Meredith, Karen A. Marrongelle
Mathematics and Statistics Faculty Publications and Presentations
We present evidence that although students’ mathematical skills in introductory calculus-based physics classes may not be readily applied in physics contexts, these students have strong mathematical resources on which to build effective instruction. Our evidence is based on clinical interviews of problem solving in electrostatics, which are analyzed using the framework of Sherin’s symbolic forms. We find that students use notions of “dependence” and “parts-of-a-whole” to successfully guide their work, even in novel situations. We also present evidence that students’ naive conceptions of the limit may prevent them from viewing integrals as sums.
Simpol.1: A Simple Group Contribution Method For Predicting Vapor Pressures And Enthalpies Of Vaporization Of Multifunctional Organic Compounds, James F. Pankow, William E. Asher
Simpol.1: A Simple Group Contribution Method For Predicting Vapor Pressures And Enthalpies Of Vaporization Of Multifunctional Organic Compounds, James F. Pankow, William E. Asher
Physics Faculty Publications and Presentations
The SIMPOL.1 group contribution method is developed for predicting the liquid vapor pressure poL (atm) and enthalpy of vaporization Δ Hvap (kJ mol-1) of organic compounds as functions of temperature (T). For each compound i, the method assumes log10poL,i (T)=∑kνk,ibk(T) where νk,i is the number of groups of type k, and bk (T) is the contribution to log10poL,i (T) by each group of type k. A …
Unipolar Transport And Interface Charge Transfer In Nanostructured Cdte/Polymer Hybrid Films, Rolf Kӧnenkamp, Robert Meier, Robert Campbell Word, Athavan Nadarajah
Unipolar Transport And Interface Charge Transfer In Nanostructured Cdte/Polymer Hybrid Films, Rolf Kӧnenkamp, Robert Meier, Robert Campbell Word, Athavan Nadarajah
Physics Faculty Publications and Presentations
We report detailed photoconductance measurements on hybrid semiconductor films consisting of CdTe nanoparticles in a poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene (MEH-PPV) matrix. Our results show that a staggered band alignment between organic and inorganic semiconductors produces an efficient separation of photoexcited electron-hole pairs and promotes a unipolar transport in each of the semiconductors. Hole drift mobilities in the MEH-PPV film and electron drift mobilities in the CdTe nanoparticle network are determined. We find clear evidence for the transport in the two phases of the hybrid film to be electrically uncoupled, and we conclude that these properties can lead to improved electron transport properties.
Structural Identification Of Cubic Iron-Oxide Nanocrystal Mixtures: X-Ray Powder Diffraction Versus Quasi-Kinematic Transmission Electron Microscopy, Peter Moeck
Physics Faculty Publications and Presentations
Two novel (and proprietary) strategies for the structural identification of a nanocrystal from either a single high-resolution (HR) transmission electron microscopy (TEM) image or a single precession electron diffraction pattern are proposed and their advantages discussed in comparison to structural fingerprinting from powder X-ray diffraction patterns. Simulations for cubic magnetite and maghemite nanocrystals are used as examples.
Dark Current Measurements In A Cmos Imager, William C. Porter, Bradley Kopp, Justin Charles Dunlap, Ralf Widenhorn, Erik Bodegom
Dark Current Measurements In A Cmos Imager, William C. Porter, Bradley Kopp, Justin Charles Dunlap, Ralf Widenhorn, Erik Bodegom
Physics Faculty Publications and Presentations
We present data for the dark current of a commercially available CMOS image sensor for different gain settings and bias offsets over the temperature range of 295 to 340 K and exposure times of 0 to 500 ms. The analysis of hot pixels shows two different sources of dark current. One source results in hot pixels with high but constant count for exposure times smaller than the frame time. Other hot pixels exhibit a linear increase with exposure time. We discuss how these hot pixels can be used to calculate the dark current for all pixels. Finally, we show that …
Measurements Of Dark Current In A Ccd Imager During Light Exposures, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom
Measurements Of Dark Current In A Ccd Imager During Light Exposures, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom
Physics Faculty Publications and Presentations
Thermal excitation of electrons is a major source of noise in Charge-Coupled Device (CCD) imagers. Those electrons are generated even in the absence of light, hence the name dark current. Dark current is particularly important for long exposure times and elevated temperatures. The standard procedure to correct for dark current is to take several pictures under the same condition as the real image, except with the shutter closed. The resulting dark frame is later subtracted from the exposed image. We address the question of whether the dark current produced in an image taken with a closed shutter is identical to …
Controlled Fabrication Of High-Yield Cds Nanostructures By Compartment Arrangement, Joshua M. Green, Juno Lawrance, Jun Jiao
Controlled Fabrication Of High-Yield Cds Nanostructures By Compartment Arrangement, Joshua M. Green, Juno Lawrance, Jun Jiao
Physics Faculty Publications and Presentations
High-yield, high-purity CdS nanostructures were synthesized in a turf-like configuration using an improved vapor-liquid-solid method. To increase the yield, a compartment arrangement was employed. The specific kind of nanostructure fabricated was found to be directly dependent on the temperature in the compartment. Along with the high-yield growth of CdS nanorods, nanowires, and nanobelts, intertwined structures were also observed, and the electron field emission property of the intertwined structures was investigated and compared with that of other type of nanostructures. Photoluminescence measurements at 10 K showed a peak emission from the CdS nanostructures at 485 nm.
New Particle Formation In The Front Range Of The Colorado Rocky Mountains, Micahel Boy, Thomas Karl, Andrew Turnipseed, Roy Lee Mauldin, Edward Kosciuch, James Greenberg, Jeff Rathbone, James Smith, Andreas Held, Kelley Barsanti, Alex Guenther
New Particle Formation In The Front Range Of The Colorado Rocky Mountains, Micahel Boy, Thomas Karl, Andrew Turnipseed, Roy Lee Mauldin, Edward Kosciuch, James Greenberg, Jeff Rathbone, James Smith, Andreas Held, Kelley Barsanti, Alex Guenther
Civil and Environmental Engineering Faculty Publications and Presentations
New particle formation is of interest because of its influence on the properties of aerosol population, and due to the possible contribution of newly formed particles to cloud condensation nuclei. Currently no conclusive evidence exists as to the mechanism or mechanisms of nucleation and subsequent particle growth. However, nucleation rates exhibit a clear dependence on ambient sulphuric acid concentrations and particle growth is often attributed to the condensation of organic vapours. A detailed study of new particle formation in the Front Range of the Colorado Rocky Mountains is presented here. Gas and particle measurement data for 32 days was analyzed …