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Machine Learning Prediction Of Glass Transition Temperature Of Conjugated Polymers From Chemical Structure, Amirhadi Alesadi, Zhiqiang Cao, Zhaofan Li, Song Zhang, Haoyu Zhao, Xiaodan Gu, Wenjie Xia
Machine Learning Prediction Of Glass Transition Temperature Of Conjugated Polymers From Chemical Structure, Amirhadi Alesadi, Zhiqiang Cao, Zhaofan Li, Song Zhang, Haoyu Zhao, Xiaodan Gu, Wenjie Xia
Faculty Publications
Predicting the glass transition temperature (Tg) is of critical importance as it governs the thermomechanical performance of conjugated polymers (CPs). Here, we report a predictive modeling framework to predict Tg of CPs through the integration of machine learning (ML), molecular dynamics (MD) simulations, and experiments. With 154 Tg data collected, an ML model is developed by taking simplified “geometry” of six chemical building blocks as molecular features, where side-chain fraction, isolated rings, fused rings, and bridged rings features are identified as the dominant ones for Tg. MD simulations further unravel the fundamental roles …
Tailored Porous Carbons Enabled By Persistent Micelles With Glassy Cores, Eric R. Williams, Paige L. Mcmahon, Joseph E. Reynolds Iii, Jonathan L. Snider, Vitalie Stavila, Mark Allendorf, Morgan Stefik
Tailored Porous Carbons Enabled By Persistent Micelles With Glassy Cores, Eric R. Williams, Paige L. Mcmahon, Joseph E. Reynolds Iii, Jonathan L. Snider, Vitalie Stavila, Mark Allendorf, Morgan Stefik
Faculty Publications
Porous nanoscale carbonaceous materials are widely employed for catalysis, separations, and electrochemical devices where device performance often relies upon specific and well-defined regular feature sizes. The use of block polymers as templates has enabled affordable and scalable production of diverse porous carbons. However, popular carbon preparations use equilibrating micelles which can change dimensions in response to the processing environment. Thus, polymer methods have not yet demonstrated carbon nanomaterials with constant average template diameter and tailored wall thickness. In contrast, persistent micelle templates (PMTs) use kinetic control to preserve constant micelle template diameters, and thus PMT has enabled constant pore diameter …
The Malina Oceanographic Expedition: How Do Changes In Ice Cover, Permafrost And Uv Radiation Impact Biodiversity And Biogeochemical Fluxes In The Arctic Ocean?, Philippe Massicotte, Rainer M.W. Amon, Antoine David, Sergio Balzano, Simon Bélanger, Ronald Benner, Dominique Boeuf, Annick Bricaud, Flavienne Bruyant, Gwenaëlle Chaillou, Malik Chami, Bruno Charrière, Jing Chen, Hervé Claustre, Pierre Coupel, Nicole Delsaut, David Doxaran, Jens Ehn, Cédric Fichot, Marie-Hélène Forget, Et. Al.
The Malina Oceanographic Expedition: How Do Changes In Ice Cover, Permafrost And Uv Radiation Impact Biodiversity And Biogeochemical Fluxes In The Arctic Ocean?, Philippe Massicotte, Rainer M.W. Amon, Antoine David, Sergio Balzano, Simon Bélanger, Ronald Benner, Dominique Boeuf, Annick Bricaud, Flavienne Bruyant, Gwenaëlle Chaillou, Malik Chami, Bruno Charrière, Jing Chen, Hervé Claustre, Pierre Coupel, Nicole Delsaut, David Doxaran, Jens Ehn, Cédric Fichot, Marie-Hélène Forget, Et. Al.
Faculty Publications
The MALINA oceanographic campaign was conducted during summer 2009 to investigate the carbon stocks and the processes controlling the carbon fluxes in the Mackenzie River estuary and the Beaufort Sea. During the campaign, an extensive suite of physical, chemical and biological variables were measured across seven shelf-basin transects (south-north) to capture the meridional gradient between the estuary and the open ocean. Key variables such as temperature, absolute salinity, radiance, irradiance, nutrient concentrations, chlorophyll a concentration, bacteria, phytoplankton and zooplankton abundance and taxonomy, and carbon stocks and fluxes were routinely measured onboard the Canadian research icebreaker CCGS Amundsen and from a …
Effect Of Strain On Charge Density Wave Order In The Holstein Model, Benjami Cohen-Stead, Natanael Costa, Ehsan Khatami, Richard Scalettar
Effect Of Strain On Charge Density Wave Order In The Holstein Model, Benjami Cohen-Stead, Natanael Costa, Ehsan Khatami, Richard Scalettar
Faculty Publications
We investigate charge ordering in the Holstein model in the presence of anisotropic hopping, tx,ty=1-δ,1+δ, as a model of the effect of strain on charge-density-wave (CDW) materials. Using quantum Monte Carlo simulations, we show that the CDW transition temperature is relatively insensitive to moderate anisotropy δ 0.3, but begins to decrease more rapidly at δ 0.4. However, the density correlations, as well as the kinetic energies parallel and perpendicular to the compressional axis, change significantly for moderate δ. Accompanying mean-field theory calculations show a similar qualitative structure, with the transition temperature relatively constant at small δ, and a more rapid …
The Effects Of Ambient Temperature And Lighting Intensity On Wheel-Running Behavior In A Diurnal Rodent, The Nile Grass Rat (Arvicanthis Niloticus), Garrett M. Fogo, Alyssa M. Goodwin, Ohanes S. Khacherian, Brandi J. Ledbetter, Andrew J. Gall
The Effects Of Ambient Temperature And Lighting Intensity On Wheel-Running Behavior In A Diurnal Rodent, The Nile Grass Rat (Arvicanthis Niloticus), Garrett M. Fogo, Alyssa M. Goodwin, Ohanes S. Khacherian, Brandi J. Ledbetter, Andrew J. Gall
Faculty Publications
Environmental conditions, such as the light-dark cycle and temperature, affect the display of circadian rhythmicity and locomotor activity patterns in mammals. Here, we tested the hypothesis that manipulating these environmental conditions would affect wheel-running activity patterns in a diurnal rodent, the Nile grass rat (Arvicanthis niloticus). Grass rats are diurnal in the field, however, a subset switch from a day-active pattern to a night-active pattern of activity after the introduction of a running wheel. The mechanism of this chronotype switch remains largely unknown. In the present study, grass rats were presented with running wheels in 12:12 light-dark conditions. First, subjects …
Cosmopolitan Species As Models For Ecophysiological Responses To Global Change: The Common Reed Phragmites Australis, Franziska Eller, Hana Skálová, Joshua S. Caplan, Ganesh P. Bhattarai, Melissa K. Burger, James T. Cronin, Wen Yong Guo, Xiao Guo, Eric L.G. Hazelton, Karin M. Kettenring, Carla Lambertini, Melissa K. Mccormick, Laura A. Meyerson, Thomas J. Mozdzer, Petr Pyšek, Brian K. Sorrell, Dennis F. Whigham, Hans Brix
Cosmopolitan Species As Models For Ecophysiological Responses To Global Change: The Common Reed Phragmites Australis, Franziska Eller, Hana Skálová, Joshua S. Caplan, Ganesh P. Bhattarai, Melissa K. Burger, James T. Cronin, Wen Yong Guo, Xiao Guo, Eric L.G. Hazelton, Karin M. Kettenring, Carla Lambertini, Melissa K. Mccormick, Laura A. Meyerson, Thomas J. Mozdzer, Petr Pyšek, Brian K. Sorrell, Dennis F. Whigham, Hans Brix
Faculty Publications
© 2017 Eller, Skálová, Caplan, Bhattarai, Burger, Cronin, Guo, Guo, Hazelton, Kettenring, Lambertini, McCormick, Meyerson, Mozdzer, Pyšek, Sorrell, Whigham and Brix. Phragmites australis is a cosmopolitan grass and often the dominant species in the ecosystems it inhabits. Due to high intraspecific diversity and phenotypic plasticity, P. australis has an extensive ecological amplitude and a great capacity to acclimate to adverse environmental conditions; it can therefore offer valuable insights into plant responses to global change. Here we review the ecology and ecophysiology of prominent P. australis lineages and their responses to multiple forms of global change. Key findings of our review …
Mechanistic Species Distribution Modelling As A Link Between Physiology And Conservation, Tyler G. Evans, Sarah E. Diamond, Morgan W. Kelly
Mechanistic Species Distribution Modelling As A Link Between Physiology And Conservation, Tyler G. Evans, Sarah E. Diamond, Morgan W. Kelly
Faculty Publications
© The Author 2015. Climate change conservation planning relies heavily on correlative species distribution models that estimate future areas of occupancy based on environmental conditions encountered in present-day ranges. The approach benefits from rapid assessment of vulnerability over a large number of organisms, but can have poor predictive power when transposed to novel environments and reveals little in the way of causal mechanisms that define changes in species distribution or abundance. Having conservation planning rely largely on this single approach also increases the risk of policy failure. Mechanistic models that are parameterized with physiological information are expected to be more …
Interannual Variability Of Wintertime Temperature On The Inner Continental Shelf Of The Middle Atlantic Bight, Thomas Connolly, Steven Lentz
Interannual Variability Of Wintertime Temperature On The Inner Continental Shelf Of The Middle Atlantic Bight, Thomas Connolly, Steven Lentz
Faculty Publications
The shallow depth of the inner continental shelf allows for rapid adjustment of the ocean to air-sea exchange of heat and momentum compared with offshore locations. Observations during 2001–2013 are used to evaluate the contributions of air-sea heat flux and oceanic advection to interannual variability of inner-shelf temperature in the Middle Atlantic Bight. Wintertime processes are important for interpreting regional interannual variability at nearshore locations since winter anomalies account for 69–77% of the variance of the annual anomalies and are correlated over broad along-shelf scales, from New England to North Carolina. At the Martha's Vineyard Coastal Observatory on the 12 …
Dynamics Of Methane Ebullition From A Peat Monolith Revealed From A Dynamic Flux Chamber System, Zhongjie Yu, Lee D. Slater, Karina V. R. Schafer, Andrew S. Reeve, Ruth K. Varner
Dynamics Of Methane Ebullition From A Peat Monolith Revealed From A Dynamic Flux Chamber System, Zhongjie Yu, Lee D. Slater, Karina V. R. Schafer, Andrew S. Reeve, Ruth K. Varner
Faculty Publications
Methane (CH4) ebullition in northern peatlands is poorly quantified in part due to its high spatiotemporal variability. In this study, a dynamic flux chamber (DFC) system was used to continuously measure CH4 fluxes from a monolith of near‐surface Sphagnum peat at the laboratory scale to understand the complex behavior of CH4 ebullition. Coincident transmission ground penetrating radar measurements of gas content were also acquired at three depths within the monolith. A graphical method was developed to separate diffusion, steady ebullition, and episodic ebullition fluxes from the total CH4 flux recorded and to identify the timing and CH4 content of individual …
New Advances In Post-Installed Subsea Monitoring Systems For Structural And Flow Assurance Evaluation, Reza Asgharzadeh Shishavan, David Brower, John Hedengren, Alexis Brower
New Advances In Post-Installed Subsea Monitoring Systems For Structural And Flow Assurance Evaluation, Reza Asgharzadeh Shishavan, David Brower, John Hedengren, Alexis Brower
Faculty Publications
An overview of fiber optic sensors for temperature, pressure, strain, and fatigue of subsea structures is provided. Current progress details efforts to ensure proper installation and bonding to existing risers, flow-lines, mooring lines, trees, and other structures in actual subsea environments. Developments include clamp prototypes, bonding techniques, long-term fatigue analysis, sensor calibration, and temperature compensation. Fiber optic technology in subsea monitoring began over 20 years ago by migrating expertise from decommissioning of rocket motors. The first installations were on new installations of subsea pipelines, production risers, and drilling risers to measure strain and vibration for fatigue life monitoring. Of particular …
Intrinsic And Extrinsic Factors Influence Expression Of Defensive Behavior In Plains Hog‐Nosed Snakes [Abstract], Andrew M. Durso, Stephen J. Mullin
Intrinsic And Extrinsic Factors Influence Expression Of Defensive Behavior In Plains Hog‐Nosed Snakes [Abstract], Andrew M. Durso, Stephen J. Mullin
Faculty Publications
No abstract provided.
Finite-Temperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol
Finite-Temperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol
Faculty Publications
We study finite-temperature properties of strongly interacting fermions in the honeycomb lattice using numerical linked-cluster expansions and determinantal quantum Monte Carlo simulations. We analyze a number of thermodynamic quantities, including the entropy, the specific heat, uniform and staggered spin susceptibilities, short-range spin correlations, and the double occupancy at and away from half filling. We examine the viability of adiabatic cooling by increasing the interaction strength for homogeneous as well as for trapped systems. For the homogeneous case, this process is found to be more efficient at finite doping than at half filling. That, in turn, leads to an efficient adiabatic …
Advanced Deepwater Monitoring System, David Brower, John Hedengren, Reza Asgharzadeh Shishavan, Alexis Brower
Advanced Deepwater Monitoring System, David Brower, John Hedengren, Reza Asgharzadeh Shishavan, Alexis Brower
Faculty Publications
This study investigates new methods to improve deepwater monitoring and addresses installation of advanced sensors on ”already deployed” risers, flowlines, trees, and other deepwater devices. A major shortcoming of post installed monitoring systems in subsea is poor coupling between the sensor and structure. This study provided methods to overcome this problem. Both field testing in subsea environments and laboratory testing were performed. Test articles included actual flowline pipe and steel catenary risers up to twenty-four inches in diameter. A monitoring device resulting from this study can be installed in-situ on underwater structures and could enhance productivity and improve safety of …
Temperature And Co2 Additively Regulate Physiology, Morphology And Genomic Responses Of Larval Sea Urchins, Strongylocentrotus Purpuratus, Jacqueline L. Padilla-Gamiño, Morgan W. Kelly, Tyler G. Evans, Gretchen E. Hofmann
Temperature And Co2 Additively Regulate Physiology, Morphology And Genomic Responses Of Larval Sea Urchins, Strongylocentrotus Purpuratus, Jacqueline L. Padilla-Gamiño, Morgan W. Kelly, Tyler G. Evans, Gretchen E. Hofmann
Faculty Publications
Ocean warming and ocean acidification, both consequences of anthropogenic production of CO2, will combine to influence the physiological performance of many species in the marine environment. In this study, we used an integrative approach to forecast the impact of future ocean conditions on larval purple sea urchins (Strongylocentrotus purpuratus) from the northeast Pacific Ocean.In laboratory experiments that simulated ocean warming and ocean acidification, we examined larval development, skeletal growth, metabolism and patterns of gene expression using an orthogonal comparison of two temperature (138C and 188C) and pCO2 (400 and 1100 matm) conditions. Simultaneous exposure to increased temperature and pCO2 significantly …
Temperature Responses Of Carbon Monoxide And Hydrogen Uptake By Vegetated And Unvegetated Volcanic Cinders, Caitlin E. King, Gary M. King
Temperature Responses Of Carbon Monoxide And Hydrogen Uptake By Vegetated And Unvegetated Volcanic Cinders, Caitlin E. King, Gary M. King
Faculty Publications
Ecosystem succession on a large deposit of volcanic cinders emplaced on Kilauea Volcano in 1959 has resulted in a mosaic of closed-canopy forested patches and contiguous unvegetated patches. Unvegetated and unshaded surface cinders (Bare) experience substantial diurnal temperature oscillations ranging from moderate (16°C) to extreme (55°C) conditions. The surface material of adjacent vegetated patches (Canopy) experiences much smaller fluctuations (14-25°C) due to shading. To determine whether surface material from these sites showed adaptations by carbon monoxide (CO) and hydrogen (H2) consumption to changes in ambient temperature regimes accompanying succession, we measured responses of CO and H2 uptake to short-term variations …
"Ultracold" Neutral Plasmas At Room Temperature, N. Heilmann, J. B. Peatross, Scott D. Bergeson
"Ultracold" Neutral Plasmas At Room Temperature, N. Heilmann, J. B. Peatross, Scott D. Bergeson
Faculty Publications
We report a measurement of the electron temperature in a plasma generated by a high-intensity laser focused into a jet of neon. The 15 eV electron temperature is determined using an analytic solution of the plasma equations assuming local thermodynamic equilibrium, initially developed for ultracold neutral plasmas. We show that this analysis method accurately reproduces more sophisticated plasma simulations in our temperature and density range. While our plasma temperatures are far outside the typical "ultracold" regime, the ion temperature is determined by the plasma density through disorder-induced heating just as in ultracold neutral plasma experiments. Based on our results, we …
Thermodynamics Of Strongly Interacting Fermions In Two-Dimensional Optical Lattices, Ehsan Khatami, Marcos Rigol
Thermodynamics Of Strongly Interacting Fermions In Two-Dimensional Optical Lattices, Ehsan Khatami, Marcos Rigol
Faculty Publications
We study finite-temperature properties of strongly correlated fermions in two-dimensional optical lattices by means of numerical linked cluster expansions, a computational technique that allows one to obtain exact results in the thermodynamic limit. We focus our analysis on the strongly interacting regime, where the on-site repulsion is of the order of or greater than the band width. We compute the equation of state, double occupancy, entropy, uniform susceptibility, and spin correlations for temperatures that are similar to or below the ones achieved in current optical lattice experiments. We provide a quantitative analysis of adiabatic cooling of trapped fermions in two …
Density And Temperature Scaling Of Disorder-Induced Heating In Ultracold Plasmas, Scott D. Bergeson, A. Denning, M. Lyon, F. Robicheaux
Density And Temperature Scaling Of Disorder-Induced Heating In Ultracold Plasmas, Scott D. Bergeson, A. Denning, M. Lyon, F. Robicheaux
Faculty Publications
We report measurements and simulations of disorder-induced heating in ultracold neutral plasmas. Fluorescence from plasma ions is excited using a detuned probe laser beam while the plasma relaxes from its initially disordered nonequilibrium state. This method probes the wings of the ion velocity distribution. The simulations yield information on time-evolving plasma parameters that are difficult to measure directly and make it possible to connect the fluorescence signal to the rms velocity distribution. The disorder-induced heating signal can be used to estimate the electron and ion temperatures ~100 ns after the plasma is created. This is particularly interesting for plasmas in …
Quantum Criticality Due To Incipient Phase Separation In The Two-Dimensional Hubbard Model, Ehsan Khatami, K. Mikelsons, D. Galanakis, A. Macridin, J. Moreno, R. Scalettar, M. Jarrell
Quantum Criticality Due To Incipient Phase Separation In The Two-Dimensional Hubbard Model, Ehsan Khatami, K. Mikelsons, D. Galanakis, A. Macridin, J. Moreno, R. Scalettar, M. Jarrell
Faculty Publications
We investigate the two-dimensional Hubbard model with next-nearest-neighbor hopping, t′, using the dynamical cluster approximation. We confirm the existence of a first-order phase-separation transition terminating at a second-order critical point at filling nc(t′) and temperature Tps(t′). We find that as t′ approaches zero, Tps(t′) vanishes and nc(t′) approaches the filling associated with the quantum critical point separating the Fermi liquid from the pseudogap phase. We propose that the quantum critical point under the superconducting dome is the zero-temperature limit of the line of second-order critical points.
High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee
High-Temperature Calcium Vapor Cell For Spectroscopy On The 4s2 1s0-4s4p 3p1 Intercombination Line, Christopher J. Erickson, Brian Neyenhuis, Dallin S. Durfee
Faculty Publications
We have demonstrated a high-temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual-chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high-temperature vacuum valves and glass-to-metal seals. We have observed over 50% absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the broadening resulted in higher signal-to-noise ratios by allowing us to probe the atoms with intensities much greater than the 0.2µW/cm2 saturation intensity of the unbroadened transition. The techniques presented in this …
Bergmann's Rule In Ectotherms: A Test Using Freshwater Fishes, Mark C. Belk, Derek D. Houston
Bergmann's Rule In Ectotherms: A Test Using Freshwater Fishes, Mark C. Belk, Derek D. Houston
Faculty Publications
Understanding patterns of variation in body size within and among species is a central question in evolutionary ecology (Schlichting and Pigliucci 1998). The most well known pattern of variation in body size is Bergmann's rule (Bergmann 1847; Mayr 1956). The intraspecific version of Bergmann's rule holds that within endothermic species, body size increases with increasing latitude (or decreasing temperature; Blackburn et al. 1999; Ashton et al. 2000). In general, mammals conform to this rule (Ashton et al. 2000).
Creation Of An Ultracold Neutral Plasma, Scott D. Bergeson, T. C. Killian, S. Kulin, L. A. Orozco, C. Orzel, S. L. Rolston
Creation Of An Ultracold Neutral Plasma, Scott D. Bergeson, T. C. Killian, S. Kulin, L. A. Orozco, C. Orzel, S. L. Rolston
Faculty Publications
We report the creation of an ultracold neutral plasma by photoionization of laser-cooled xenon atoms. The charge carrier density is as high as 2×10^9 cm^-3, and the temperatures of electrons and ions are as low as 100 mK and 10 uK, respectively. Plasma behavior is evident in the trapping of electrons by the positive ion cloud when the Debye screening length becomes smaller than the size of the sample. We produce plasmas with parameters such that both electrons and ions are strongly coupled.
Influence Of Some Design Variables On The Thermal Behavior Of A Lithium‐Ion Cell, Gerardine G. Botte, Bradley A. Johnson, Ralph E. White
Influence Of Some Design Variables On The Thermal Behavior Of A Lithium‐Ion Cell, Gerardine G. Botte, Bradley A. Johnson, Ralph E. White
Faculty Publications
No abstract provided.
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Faculty Publications
A catalog of mean values of [Fe/H] for evolved G and K stars is described. The zero point for the catalog entries has been established by using differential analyses. Literature sources for those entries are included in the catalog. The mean values are given with rms errors and numbers of degrees of freedom, and a simple example of the use of these statistical data is given. For a number of the stars with entries in the catalog, temperatures have been determined. A separate catalog containing those data is briefly described.
Modeling Physical And Chemical Climate Of The Northeastern United States For A Geographic Information System, Scott V. Ollinger, John D. Aber, Anthony C. Federer, Gary M. Lovett, Jennifer M. Ellis
Modeling Physical And Chemical Climate Of The Northeastern United States For A Geographic Information System, Scott V. Ollinger, John D. Aber, Anthony C. Federer, Gary M. Lovett, Jennifer M. Ellis
Faculty Publications
A model of physical and chemical climate was developed for New York and New England that can be used in a GIs for integration with ecosystem models. The variables included are monthly average maximum and minimum daily temperatures, precipitation, humidity, and solar radiation, as well as annual atmospheric deposition of sulfur and nitrogen. Equations generated from regional data bases were combined with a digital elevation model of the region to generate digital coverages of each variable.
Thermal Characteristics Of A Nickel-Hydrogen Battery, Junbom Kim, T. V. Nguyen, Ralph E. White
Thermal Characteristics Of A Nickel-Hydrogen Battery, Junbom Kim, T. V. Nguyen, Ralph E. White
Faculty Publications
The maximum allowable temperature difference inside a nickel-hydrogen battery to avoid water relocation was calculated by using a graphical method together with a vapor pressure vs. temperature correlation equation for water vapor over potassium hydroxide solution. An equation was developed for this maximum allowable temperature difference for vessel-wall temperatures from 0 to 30°C and potassium hydroxide concentrations from 20 to 32%. A heat-generation equation for the nickel-hydrogen battery was used to investigate the effect of the location of heat generation on the maximum temperature in the cell and the temperature distribution in the cell.
Photoconductive Characterization Of Znxcd1-Xte (0≤X≤0.25) Single Crystal Alloys, David D. Allred, Elías López-Cruz, Jesus González-Hernández, Worth P. Allred
Photoconductive Characterization Of Znxcd1-Xte (0≤X≤0.25) Single Crystal Alloys, David D. Allred, Elías López-Cruz, Jesus González-Hernández, Worth P. Allred
Faculty Publications
Large grain polycrystalline and single crystals of ZnxCd1-xTe grown by a modified Bridgman method were studied using the photoluminescence and photoconductivity techniques. The temperature dependence of the band gap, as determined by photoluminescence, follows the Varshni equation for measuring temperature in the range of 15-290 K. One of the fitted parameters, the Debye temperature, monotonically decreases with the increase of the atomic zinc concentration. A close correlation between the photoluminescence and photoconductivity measurements is also found. Samples in which the photoluminescence spectra exhibit emission bands associated to cadmium vacancies and other structural defects, show a photoresponse curve which includes, in …
A Two-Dimensional Mathematical Model Of A Porous Lead Dioxide Electrode In A Lead-Acid Cell, E. C. Dimpault-Darcy, T. V. Nguyen, Ralph E. White
A Two-Dimensional Mathematical Model Of A Porous Lead Dioxide Electrode In A Lead-Acid Cell, E. C. Dimpault-Darcy, T. V. Nguyen, Ralph E. White
Faculty Publications
A two-dimensional mathematical model is presented for a lead dioxide electrode in a lead-acid cell. It is used to simulate the time dependent behavior of the electrode during discharge. The model contains six dependent variables: the concentration of the acid electrolyte, the porosity, the electrical potentials of the solid and solution phases, and the two directional components of the current density in the electrolyte. The effect of the electrode grid was included by varying the conductivity of the solid. Parameters such as electrode conductivity, electrode dimensions, and temperature are investigated to understand their effects on electrode discharge performance.
Superconductivity At 155 K, David D. Allred, S. R. Ovshinsky, R. T. Young, G. Demaggio, G. A. Van Der Leeden
Superconductivity At 155 K, David D. Allred, S. R. Ovshinsky, R. T. Young, G. Demaggio, G. A. Van Der Leeden
Faculty Publications
Transition to a superconducting zero-resistance state at 155 K is observed for the first time in bulk material. A new five-element compound has been synthesized with nominal composition Y1Ba2Cu3F2Oy. Fluorine plays a critical role in achieving this effect. X-ray diffraction and electron microprobe analysis indicate that the samples are multiphasic. Evidence is presented that the samples contain superconducting phases with onset temperatures considerably above 155 K. Magnetic measurements suggest a flux-trapping effect below 260 K, and diamagnetic deviations from Curie-Weiss behavior in the range from 250 K≤T≤100 K indicate that Meissner effect in a small superconducting volume fraction.
A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White
A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White
Faculty Publications
A mathematical model of a lead-acid cell is presented which includes the modeling of porous electrodes and various physical phenomena in detail. The model is used to study the dynamic behavior of the acid concentration, the porosity of the electrodes, and the state of charge of the cell during discharge, rest, and charge. The dependence of the performance of the cell on electrode thicknesses and operating temperature is also investigated.