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Flow Stability of Gas-Solids Suspensions: Final Report

Description: From abstract: One of the principal purposes of the work reported was to study the stability of gas-solids suspensions in the presence of a thermal gradient. Previously reported experience with unstable suspensions is summarized.
Date: February 1964
Creator: Wachtell, G. P. & Waggener, J. P.
Partner: UNT Libraries Government Documents Department

Systems Interoperability and Collaborative Development for Web Archiving - Filling Gaps in the IMLS National Digital Platform

Description: This presentation provides an overview of the beginning stages of the IMLS funded two-year web archiving research project with Internet Archive, Stanford University Libraries, University of North Texas, and Rutgers University.
Date: May 25, 2016
Creator: Phillips, Mark Edward & Mumma, Courtney
Partner: UNT Libraries Digital Projects Unit

Rational Design of Metal-organic Electronic Devices: a Computational Perspective

Description: Organic and organometallic electronic materials continue to attract considerable attention among researchers due to their cost effectiveness, high flexibility, low temperature processing conditions and the continuous emergence of new semiconducting materials with tailored electronic properties. In addition, organic semiconductors can be used in a variety of important technological devices such as solar cells, field-effect transistors (FETs), flash memory, radio frequency identification (RFID) tags, light emitting diodes (LEDs), etc. However, organic materials have thus far not achieved the reliability and carrier mobility obtainable with inorganic silicon-based devices. Hence, there is a need for finding alternative electronic materials other than organic semiconductors to overcome the problems of inferior stability and performance. In this dissertation, I research the development of new transition metal based electronic materials which due to the presence of metal-metal, metal-?, and ?-? interactions may give rise to superior electronic and chemical properties versus their organic counterparts. Specifically, I performed computational modeling studies on platinum based charge transfer complexes and d10 cyclo-[M(?-L)]3 trimers (M = Ag, Au and L = monoanionic bidentate bridging (C/N~C/N) ligand). The research done is aimed to guide experimental chemists to make rational choices of metals, ligands, substituents in synthesizing novel organometallic electronic materials. Furthermore, the calculations presented here propose novel ways to tune the geometric, electronic, spectroscopic, and conduction properties in semiconducting materials. In addition to novel material development, electronic device performance can be improved by making a judicious choice of device components. I have studied the interfaces of a p-type metal-organic semiconductor viz cyclo-[Au(ยต-Pz)]3 trimer with metal electrodes at atomic and surface levels. This work was aimed to guide the device engineers to choose the appropriate metal electrodes considering the chemical interactions at the interface. Additionally, the calculations performed on the interfaces provided valuable insight into binding energies, charge redistribution, change in the energy ...
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: December 2012
Creator: Chilukuri, Bhaskar
Partner: UNT Libraries

Second-order method for interface reconstruction in orthogonal coordinate systems

Description: We present a method in two-dimensions for reconstructing an interface from a distribution of volume fractions in a general orthogonal coordinate system. The method, in a cell by cell fashion, approximates the interface curve by a linear pro le. The approach requires only local volume fraction information for the reconstruction. An integral formulation is used that accounts for the orthogonal coordinate system in a natural way. We use nit different to approximate the slop of the required interface while retaining at worst second order accuracy for general interface orientations and an exact representation for coordinate system aligned o
Date: December 23, 1998
Creator: Colella, P.; Graves, D. T. & Greenough, J. G.
Partner: UNT Libraries Government Documents Department

Metal-On-Metal Bonding and Rebonding Revisited

Description: Density-functional calculations for a wide variety of metals show that, contrary to the rebonding view of adsorbate bonding, addimers do not have notably longer surface bonds than adatoms, do not reside farther above the surface, and do not meet the rebonding arguments for augmented mobility. Rebonding concepts are found to have some utility in explaining addimer stability.
Date: February 23, 1999
Creator: Bogicevic, A.
Partner: UNT Libraries Government Documents Department

Apparent Charge Transfer at Semiconductor Surfaces

Description: We investigate the apparent charge transfer between adatoms in the GeXPb[l.XjGe(lll) interface both experimentally and theoretically. Scanning tunneling microscopy and surface core level measurements suggest significant charge transfer from the Ge adatoms to the Pb adatoms. However, first-principles calculations unambiguously find that the total electronic displacement is negligibly small, and that the results of published experiments can be explained as a result of bond rearrangement.
Date: May 11, 1999
Creator: Carpinelli, Joseph M.; Stumpf, Roland R. & Weitering, Hanno H.
Partner: UNT Libraries Government Documents Department

Interfacial Microstructure Formed by Reactive Metal Penetration of Al into Mullite

Description: Microstructure in the reaction interface between molten Al and dense mullite have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic-metal composites by reactive metal penetration. The reactions, which have the overall stoichiometry, 3Al#iz01~ + (8+ x)A1 + 13 AlzO~ + xA1 + 6Si, were carried out at temperatures of 900, 1100, and 1200oC for 5 minutes and 60 minutes, and 1400oC for 15 minutes. Observed phases generally were those given in the above reaction, although their proportions and interracial rnicrostructures differed strongly with reaction temperature. After reaction at 900oC, a thin Al layer separated unreacted mullite from the cx-AlzO~ and Al reaction products. No Si phase was found near the reaction front. After 5 minutes at 1100"C, the nxtction front contained Si, ct-A120~, and an aluminum oxide phase with a high concentration of Si. After 60 minutes at 11O(YC many of the cx-A120g particles were needle-shaped with a preferred orientation. After reaction at 1200oC, the reaction front contained a high density of Si particles that formed a continuous layer over many of the mullite grains. The sample reacted at 140VC for 15 minutes had a dense ct-A120J reaction layer less than 2~m thick. Some isolated Si particles were present between the a-AlzO~ layer and the unreacted mullite. Using previously measured reaction kinetics data, the observed temperature dependence of the interracial microstructure have been modeled as three sequential steps, each one of which is rate-limiting in a different temperature range.
Date: April 27, 1999
Creator: Du, T.B.; Ewsuk, K.G.; Fahrenholtz, W.G.; Loehman, R.E. & Lu, P.
Partner: UNT Libraries Government Documents Department

Shock transmission and reflection from a material interface and subsequent reflection from a hard boundary

Description: As a shock wave passes through a material interface into a region of higher density (the receiver material), a trans- mitted and reflected shock wave are both generated and the interface is set into motion. The speeds of the transmitted shock, reflected shock, and interface are related to the ini- tial shock speed and material properties via a set of coupled nonlinear equations that, in general, cannot be easily solved analytically. In this report, we derive the equations which describe this process and we document a numerical routine which solves the nonlinear equations. We then go on to solve the problem of finding the position where the interface col- lides with the transmitted shock wave once the transmitted shock wave is reflected from an impenetrable boundary lo- cated somewhere away from the initial material interface. Fi- nally, we compare the analytical predictions with the CALE simulation running in 1-D.
Date: November 20, 1998
Creator: Hurricane, O A & Miller, P L
Partner: UNT Libraries Government Documents Department

"Good" Digital Collections

Description: This Tech Talks presentation covers the principles that apply to "good" digital collections and analyzes how objects, metadata, and the user interface together create the users' experience of a collection.
Date: January 27, 2010
Creator: Alemneh, Daniel Gelaw
Partner: UNT Libraries

Operando tribochemical formation of onion-likecarbon leads to macroscale superlubricity

Description: This article demonstrates that tribochemical reactions occur even in dry conditions when hydrogenated diamond-like carbon (H-DLC) surface is slid against two-dimensional (2D) molybdenum disulfide along with nanodiamonds in dry nitrogen atmosphere.
Date: February 3, 2017
Creator: Berman, Diana; Narayanan, Badri; Cherukara, Mathew J.; Sankaranarayanan, Subramanian K.R.S.; Erdemir, Ali; Zinovev, Alexander et al.
Partner: UNT College of Engineering

Three-dimensional Information Space : An Exploration of a World Wide Web-based, Three-dimensional, Hierarchical Information Retrieval Interface Using Virtual Reality Modeling Language

Description: This study examined the differences between a 3-D, VRML search interface, similar to Cone Trees, as a front-end to Yahoo on the World Wide Web and a conventional text-based, 1-Dinterface to the same database. The study sought to determine how quickly users could find information using both interfaces, their degree of satisfaction with both search interfaces, and which interface they preferred.
Date: December 1997
Creator: Scannell, Peter
Partner: UNT Libraries

Random growth of interfaces: Statistical analysis of single columns and detection of critical events.

Description: The dynamics of growth and formation of surfaces and interfaces is becoming very important for the understanding of the origin and the behavior of a wide range of natural and industrial dynamical processes. The first part of the paper is focused on the interesting field of the random growth of surfaces and interfaces, which finds application in physics, geology, biology, economics, and engineering among others. In this part it is studied the random growth of surfaces from within the perspective of a single column, namely, the fluctuation of the column height around the mean value, which is depicted as being subordinated to a standard fluctuation-dissipation process with friction g. It is argued that the main properties of Kardar-Parisi-Zhang theory are derived by identifying the distribution of return times to y(0) = 0, which is a truncated inverse power law, with the distribution of subordination times. The agreement of the theoretical prediction with the numerical treatment of the model of ballistic deposition is remarkably good, in spite of the finite size effects affecting this model. The second part of the paper deals with the efficiency of the diffusion entropy analysis (DEA) when applied to the studies of stromatolites. In this case it is shown that this tool can be confidently used for the detection of complexity. The connection between the two studies is established by the use of the DEA itself. In fact, in both analyses, that is, the random growth of interfaces and the study of stromatolites, the method of diffusion entropy is able to detect the real scaling of the system, namely, the scaling of the process is determined by genuinely random events, also called critical events.
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Date: August 2004
Creator: Failla, Roberto
Partner: UNT Libraries

Final report for Grant DE-FG02-84ER45131

Description: This Final Report surveys the work done on understanding the properties and behavior of driven interfaces. It is presented under two topics: (1) interfaces driven in pure and perturbed Hele-Shaw cells; (2) gels, colloids, and polymer solutions as complex media for interface growth and motion. This work has contributed to the international effort to learn about nonlinear and pattern forming systems. The data have been influential as theoretical and computational groups have attempted to understand the dynamics and nonlinear processing steps and the structure-property relations of complex materials. The Hele-Shaw cell was especially productive during this period of intense interest in ''simple'' nonlinear pattern formation, providing the simplest and best understood pattern forming system which could then be complicated with changes of boundary condition or changes of fluid property to test in a controlled way the effect on pattern formation of added physical/mathematical complexity.
Date: June 7, 2001
Creator: Maher, James V.
Partner: UNT Libraries Government Documents Department

Vibrational Spectroscopy of Chromatographic Interfaces

Description: Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.
Date: March 10, 2011
Creator: Pemberton, Jeanne E.
Partner: UNT Libraries Government Documents Department