University Library FACE 2006 2006 Entries- Engineering

22nd Annual Faculty Academic Contributions Virtual Exhibit

 

The following items, arranged by the author's last name, were part of the 2006 exhibit:

"Coupled Dynamic Analysis and Equivalent Static Wind Loads on Buildings with Three-Dimensional Modes"

Xinzhong Chen, Assistant Professor in Civil Engineering

Bio: Xinzhong Chen is an Assistant Professor in Civil Engineering.  Dr. Chen earned his Dr. Eng. Civil Engineering from Kyoto University, Kyoto, Japan; his M.S. Civil Engineering from China Academy of Railway Sciences, Beijing, China; and B.S. Civil Engineering from Southwest Jiaotong University, Sichuan, China.  Dr. Chen is a member of the American Society of Civil Engineers and the American Association for Wind Engineering. 

Abstact: Buildings with either complex geometric shapes or structural systems with nocoincident centers of mass and resistance, or both, may undergo three-dimensional (3D) coupled motions when exposed to spatiotemporally varying dynamic wind loads. To capture the dynamic load effects, this paper presents a framework for the analysis of 3D coupled dynamic response of buildings and modeling of the equivalent static wind loads (ESWLs). Utilizing a representative tall building with 3D mode shapes and closely spaced frequencies, the framework for the analysis of coupled dynamic load effects and modeling of 3D ESWLs is demonstrated.

"Dynamic Wind Effects on Buildings with 3D Coupled Modes: Application of High Frequency Force Balance Measurements," Journal of Engineering Mechanics, (November 2005): 115-

Xinzhong Chen, Assistant Professor in Civil Engineering

Abstact: Contemporary high-rise buildings with complex geometric profiles and 3D coupled mode shapes often complicate the use of high frequency force balance (HFFB) technique customarily used in wind tunnel testing for uncoupled buildings. In this study, a comprehensive framework for the coupled building response analysis and the modeling of the associated equivalent static wind loads using the HFFB measurement is presented. A representative tall building with 3D coupled modes and closely spaced frequencies is utilized to demonstrate the proposed framework and to highlight the significance of cross correlation of wind loads and the intermodal coupling of modal responses on the accurate prediction of coupled building response. Additionally, delineation of the proper role of the correlation between integrated loads, modal response, and respective building response components in the evaluation of wind effects on coupled buildings is underscored.

"Proper Orthogonal Decomposition-Based Modeling, Analysis, and Simulation of Dynamic Wind Load Effects on Structures," Journal of Engineering Mechanics, vol. 131 no. 4 (April 2005): 325-339

Xinzhong Chen, Assistant Professor in Civil Engineering

Abstact: Multicorrelated stationary random processes/fields can be decomposed into a set of subprocesses by diagonalizing their covariance or cross power spectral density (XPSD) matrices through the eigenvector/modal decomposition. This proper orthogonal decomposition (POD) technique offers physically meaningful insight into the process as each eigenmode may be characterized on the basis of its spatial distribution. It also facilitates characterization and compression of a large number of multicorrelated random processes by ignoring some of the higher eigenmodes associated with smaller eigenvalues. In this paper, the theoretical background of the POD technique based on the decomposition of the covariance and the XPSD matrices is presented. A physically meaningful linkage between the wind loads and the attendant background and resonant response of structures in the POD framework is established. This helps in better understanding how structures respond to the spatiotemporally varying dynamic loads. Utilizing the POD-based modal representation, schemes for simulation and state-space modeling of random fields are presented. Finally, the accuracy and effectiveness of the reduced-order modeling in representing local and global wind loads and their effects on a wind-excited building are investigated.

"Transformation-Induced Plasticity and Cascading Structural Changes in Hexagonal Boron Nitride Under High Pressure and Shear," Applied Physics Letters, 86

Javad Hashemi, Professor in Mechanical Engineering

Bio: Dr. Hashemi is a professor of Mechanical Engineering at Texas Tech University. He received his Ph.D. from Drexel University in 1988 and joined Texas Tech University as an Assistant Professor in 1991. His research interests include Orthopedic Biomechanics, Materials, and Engineering Education. He is married to Eva Lynn and has two sons: Evan and Jonathon.

Abstact: In situ x-ray diffraction study and modeling of the degree of disorder, s, and phase transformation (PT) in hexagonal hBN were performed. It was proven that changes in s are strain-induced and that s can be used to quantify plastic strain. During the strain-induced hBN-->wurtzitic wBN PT, the transformation-induced plasticity (TRIP) was exposed and quantified. TRIP exceeds conventional plasticity by a factor of 20. Cascading structural changes were revealed. Strain-induced disorder explains why PT under hydrostatic and nonhydrostatic conditions started at the same pressure ~10  GPa. For the same disorder, plastic shear reduces PT pressure by a factor of 3–4. ©2005 American Institute of Physics

"Sex-Based Differences in the Anthropometric Characteristics of the Anterior Cruciate Ligament and Its Relation to Intercondylar Notch Geometry: A Cadaveric Study," The American Journal of Sports Medicine, 33 (2005): 1492-1498

Javad Hashemi, Professor in Mechanical Engineering

Abstact:

"Application of a Dialysis Sampler to Monitor Phytoremediation Processes," Environmental Monitoring and Assessment, vol. 107 (2005): 155-171

Andrew Jackson, Associate Professor in Civil Engineering

Bio: W. Andrew Jackson is an Associate Professor for Civil Engineering.  Dr. Jackson earned his Ph.D. in Environmental Engineering and M.S. in Environmental Engineering from Louisiana State University.  He received his B.S. in Biology from Rhodes College.  Dr. Jackson has received numerous awards, such as Civil Engineering Research of the Year (April 2004 and April 2002 ) and Lockheed Martin College of Engineering Teaching Award (May 2002).  Dr. Jackson is a member of the Association of Environmental Engineers and Science Professors (Education Committee), the Water Environment Federation, the American Chemical Society, the Society of Environmental Toxicology and Chemistry (Editorial Board), and the American Institute of Aeronautics and Astronautics. 

Abstact: A cylindrical dialysis sampler (1.2 m in length; 5 cm in diameter) was designed and constructed to sample small–scale phytoremediation processes in the root zone of poplar trees. The study site was a 183–tree plantation of hybrid poplars located at Aberdeen Proving Ground, Maryland, at the J–Field Area of Concern. The grove was planted in 1996 to intercept a chlorinated solvent plume containing 1,1,2,2–tetrachloroethane (1,1,2,2–TeCA, trichloroethene (TCE) and daughter products. Two dialysis samplers were installed: one directly in the poplar grove (approximately 0.3 m from the trunk of a mature tree) and the other outside of the grove but in the plume. Data collected included concentrations of chlorinated VOCs, organic acids, chloroacetic acids, Cl−, and dissolved gases (ethane, ethene, CH4, CO2). At the control location, the VOC profile was dominated by cis– 1,2–dichloroethene (cis–1,2–DCE) and trans–1,2–dichloroethene (trans–1,2–DCE) with concentrations ranging from 0.88-4.5 to 4.4-17.6 mg/L, respectively. Concentrations of VOCs were similar across the vertical profile. At the tree location, 1,1,2,2–TeCA and TCE were the dominant VOCs detected but as opposed to the control location were highly variable within the root zone, with the greatest variability associated with locations in the sampler where roots were observed. This highly variable profile at the tree location is indicative of VOC rhizosphere biodegradation and uptake near the active roots. This variability appears to be on the centimeter scale, emphasizing the importance of these high–resolution samplers for the study of rhizosphere influences.

"The Origin of Naturally Occurring Perchlorate: The Role of Atmospheric Processes"

Andrew Jackson, Associate Professor in Civil Engineering

Abstact: Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largely to the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (~0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. We report that perchlorate is present in many rain and snow samples. This strongly suggests that some perchlorate is formed in the atmosphere and a natural perchlorate background of atmospheric origin should exist.

"Perchlorate Accumulation in Forage and Edible Vegetation," Journal of Agricultural and Food Chemistry, 53 (2005): 369-373

Andrew Jackson, Associate Professor in Civil Engineering

Abstact: The accumulation of perchlorate in vegetation is becoming a concern, with increasing numbers of sites reporting the presence of perchlorate in groundwater and surface water. This study investigated potential perchlorate uptake and distribution by a variety of forage and edible crops in both the laboratory and the field. Perchlorate concentrations in soybean leaves grown in the greenhouse were significantly higher than perchlorate concentrations in soybean seeds and pods. Perchlorate concentrations in alfalfa grown in sand were significantly lower than those in alfalfa grown in soil. The concentration of perchlorate in tomato was lower in the fruit than the leaves. Commercially grown wheat and alfalfa samples all contained perchlorate, 0.72-8.6 mg/kg of fresh weight (FW) in the wheat stems, 0.71-4.4 mg/kg of FW in the wheat heads, and 2.9 mg/kg of FW in alfalfa. All field garden samples tested (including cucumber, cantaloupe, and tomato) that were irrigated with perchlorate-tainted water contained perchlorate at various concentrations ranging from 0.040 to 1.65 mg/kg of FW. Bioconcentration factors (BCF), ratios of plant fresh weight concentrations to estimated or measured groundwater concentrations [(μg/kg of FW)/ μg/L], were all in the same order of magnitude ranging from 215 ± 126 for wheat stems to 233 ± 264 for wheat heads and to 380 ± 89 for alfalfa. BCF for garden fruit samples were much lower (0.5-20). Results from this study highlight the potential for perchlorate exposure by routes other than drinking water.

"Perchlorate Isotope Forensics," Analtical Chemistry, Vol. 77 No. 23 (December 1, 2005): 7838-7842

Andrew Jackson, Associate Professor in Civil Engineering

Abstact: Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses (37Cl/35Cl and 18O/17O/16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method.

"Perchlorate Occurrence in the Texas southern high plains aquifer system"

Andrew Jackson, Associate Professor in Civil Engineering

Abstact: In the spring of 2002, the Texas Commission on Environmental Quality determined that perchlorate (ClO4-) was present in the ground water from the McMillan and Paul Davis well fields that supply potable water for the city of Midland. Researchers began a large-scale sampling program to determine the source(s) and distribution of perchlorate in the area’s ground water. This document summarizes the findings of a large-scale investigation in nine counties carried out from July to December 2002. This program included public water systems (PWS) wells and private wells in Andrews, Borden, Dawson, Ector, Gaines, Glasscock, Howard, Martin, and Midland counties, which occupy a total area of 23,960 km2. Water samples were tested for perchlorate and a suite of common ions. From a total of 254 wells sampled in nine counties, 179 wells (70%) had detectable perchlorate concentrations (>0.5 ppb) and 88 wells (35%) had perchlorate concentrations equal to or above 4 ppb. The highest perchlorate concentration found at a private well was 58.8 ppb in Dawson County, while the highest concentration detected for a well in PWS was 45.6 ppb in city of Midland, Midland County. Perchlorate positively correlated (α < 0.0001) with Cl-, F-, Br-, SO42-, Mg2+, and K+ but not with NO2-, NO3-, NA+, or Ca+. Research to date has identified the most likely sources to be (1) a natural mineralogical impurity; (2) agricultural fertilizers containing perchlorate; (3) in situ generation of perchlorate by electrochemical reactions; or (4) some combination of the three. This study suggests that there may be significant sources other than the traditional industrial processing of perchlorate, and the distribution of perchlorate in ground water is likely more widespread than previously suspected.

"Temporal and Spatial Variation of Perchlorate in Streambed Sediments: Results from In-situ Dialysis Samplers"

Andrew Jackson, Associate Professor in Civil Engineering

Abstact: The fate of perchlorate (ClO4−) in streambed sediments is becoming a concern due to the increasing number of groundwater and surface water contamination sites in the United States. Dialysis samplers were deployed at three sites over a period of 1 year to determine the vertical distribution of ClO4− in sediment pore water. Results indicated that the spatial and temporal ClO4− penetration into sediments could be affected by numerous factors, such as temperature, microbial degradation, ClO4− surface water concentration, and sediment physico-geological properties. In general, maximum ClO4− penetration into sediments at the studied sites was 30 cm below the sediment-water surface. The vertical sequential depletion of electron acceptors in sediments suggested that microbial reduction was responsible for ClO4− depletion in stream sediments. Biodegradation of ClO4− occurred over a seasonally variable active depth zone of 1–10 cm. Results implied that there was a rapid natural attenuation potential of perchlorate in saturated near-surface sediments.

"Balsa Wood Plate-Type Model used in Research"

Chris Letchford, Professor in Civil Engineering

Bio: Chris W. Letchford is a Professor in Civil Engineering.  Dr. Letchford earned his D.Phil, Wind Engineering, from Oxford University, Oxford England and his BE (Civil, 1st Hons), University of Queensland, Brisbane Australia.  Dr. Letchford is a member of the Australasian Wind Engineering Society, the Institution of Engineers Australia, the American Society of Civil Engineers, and a Board Member for the American Association of Wind Engineering.  Dr. Letchford as received numerous awards and honors including the President’s Award in Teaching, Texas Tech University, 2005.

Abstact:

"Investigations of Plate-type Windborne Debris. Part I: Experiments in Wind Tunnel and Full Scale," Journal of Wind Engineering and Industrial Aerodynamics, 94 (2006): 51-76

Chris Letchford, Professor in Civil Engineering

Abstact: Modeling of the trajectory of windborne debris for incorporation in wind hazard risk assessment requires the knowledge of debris aerodynamics. On-going experiments to determine the flight characteristics of various types of debris are being carried out in the Texas Tech University (TTU) wind tunnel. This paper investigates the aerodynamic characteristics of plate-type debris. Useful data are presented in dimensionless form. Empirical expressions for estimating the horizontal flight speed and distance are derived. Results from wind-tunnel experiments are in reasonable agreement with those from full-scale tests. These results can be used to validate numerical calculations of trajectories of plate-type windborne debris.

"Investigations of Plate-type Windborne Debris. Part II: Computed Trajectories," Journal of Wind Engineering and Industrial Aerodynamics, 94 (2006): 21-39

Chris Letchford, Professor in Civil Engineering

Abstact: In Part I, trajectories of plates, carried by strong winds, were studied experimentally by wind-tunnel and full-scale tests. The application is to windborne debris occurring in severe windstorms such as hurricanes. In this paper (Part II), a numerical model of square plate trajectories is described and compared with experimental data from Tachikawa, and that described in Part I. Generally, good to excellent agreement is found; lift forces induced by the Magnus effect were found to be significant in determining trajectories.

"Crystal-Amorphous and Crystal-Crystal Phase Transformations via Virtual Melting," Physical Review Letters, 95 (August 2005): 075701-1

Valery Levitas, Professor in Mechanical Engineering

Bio: A native of the USSR, Dr. Levitas holds degrees from the University of Hannover (Germany), the Insitute of electonic Manchine Building (Moscow) and the Institute of Superhard Materials (Kiev). His interest inculde phase transfomarions, hig pressure mechanics, and multiscale modeling.

Abstact: A new mechanism of crystal (c)-amorphous (a) and c-c phase transformations (PTs) and internal stress relaxation via virtual melting (VM) induced by internal stresses was justified thermodynamically and kinteically. VM removes interface friction, reduces kinetic barrier, increases atomic mobility, and can reduce thermodynamic melting temperature. We combine VM and nonequilibrium PT diagrams to develop new scenarios of c-a and c-c PTs. Results are applied for a new interpretation of c-c and c-a PT mechanisms in ice Ih and are also applicable for other materials.

"Interfacial and Volumetric Kinetics … [see Word document "FACE submissions addenda for full title]," The Journal of Chemical Physics, 124 (2006)

Valery Levitas, Professor in Mechanical Engineering

Abstact: The interfacial and volumetric kinetics of the β to δ phase transition in the energetic nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine was investigated using virtual melting growth mechanism. The energy of the internal stresses at the coherent β-δ interface was sufficient to reduce the melting temperature of the δphase by [similar to] 120 K. The melt in each transforming material point existing during an extremely short time was sufficient for stress relaxation. This was considered as a transitionally activated state rather than a thermodynamically stable melt. (12 refs.)

"Solid-solid Phase Transformation via Internal Stress-Induced Virtual Melting: Additional Confirmations," Applied Physics Letters, vol. 87 no. 19 (November 2005): 191907

Valery Levitas, Professor in Mechanical Engineering

Abstact: Recently, we predicted a mechanism of solid-solid phase transformation (PT) via virtual melting at 121 K below the melting temperature. We report additional experimental and theoretical results for PTs among three polymorphs of the energetic material HMX, α, Β, and δ that support this mechanism. In particular: (a) the predicted velocity of interface propagation for Β->δ PT and overall kinetics of δ->Β PT are in agreement with experiment; (b) the energy of internal stresses is sufficient to reduce the melting temperature from 520 to 400 K for δ->Β PT; (c) the nanocracking that appears during solidification does not change the PT thermodynamics and kinetics for the first and the second Β<->δ PT cycles; (d) δ->Β PT starts at a very small driving force; (e) δ->α and α->δ PTs do not occur above 400 K and below 461 K, respectively. © 2005 American Institute of Physics. (9 refs.)

"Thermomechanical Lattice Instability and Phase Field Theory of Martensitic Phase Transformations, Twinning and Dislocations at Large Strains," Applied Physics A, vol. 343 no. 1-3 (August 2005): 32-39

Valery Levitas, Professor in Mechanical Engineering

Abstact: Using the second law of thermodynamics, a criterion for the instability of a crystal lattice with respect to a change in order parameters is derived for finite strains and lattice rotations. An explicit relation for lattice rotation is derived. A Gibbs (Landau) potential describing martensitic phase transformations, twinning, and dislocation nucleation is derived for a prescribed nonsymmetric nominal stress tensor and small elastic strain, but finite transformation strain and rotations. The equilibrium and transformation conditions are obtained. Martensitic phase transformations in NiAl, BN and C are analyzed and the importance of finite-strain corrections is demonstrated. ©2005 Elsevier B.V. All rights reserved.

"Transformation-Induced Plasticity and Cascading Structural Changes in Hexagonal Boron Nitride Under High Pressure and Shear," Applied Physics Letters, 86

Valery Levitas, Professor in Mechanical Engineering

Abstact: In situ x-ray diffraction study and modeling of the degree of disorder, s, and phase transformation (PT) in hexagonal hBN were performed. It was proven that changes in s are strain-induced and that s can be used to quantify plastic strain. During the strain-induced hBN wurtzitic wBN PT, the transformation-induced plasticity (TRIP) was exposed and quantified. TRIP exceeds conventional plasticity by a factor of 20. Cascading structural changes were revealed. Strain-induced disorder explains why PT under hydrostatic and nonhydrostatic conditions started at the same pressure ~10 GPa. For the same disorder, plastic shear reduces PT pressure by a factor of 3–4.

"Transformation-Induced Plasticity and Cascading Structural Changes in Hexagonal Boron Nitride Under High Pressure and Shear," Applied Physics Letters, 86

Yanzhang Ma, Assistant Professor in Mechanical Engineering

Bio:

Abstact: In situ x-ray diffraction study and modeling of the degree of disorder, s, and phase transformation (PT) in hexagonal hBN were performed. It was proven that changes in s are strain-induced and that s can be used to quantify plastic strain. During the strain-induced hBN-->wurtzitic wBN PT, the transformation-induced plasticity (TRIP) was exposed and quantified. TRIP exceeds conventional plasticity by a factor of 20. Cascading structural changes were revealed. Strain-induced disorder explains why PT under hydrostatic and nonhydrostatic conditions started at the same pressure ~10  GPa. For the same disorder, plastic shear reduces PT pressure by a factor of 3–4. ©2005 American Institute of Physics

"Enhanced Deep Ultraviolet Luminescence from AlGaN Quantum Wells Grown in the Three-dimensional Mode"

Sergey Nikishin, Associate Professor in Electrical and Computer Engineering

Bio: Dr. Sergey Nikishin is an Associate Professor of Electrical and Computer Engineering.  Dr. Nikishin earned his Ph.D. in Physics and Math from St. Petersburg Polytechnic Institute, Russia, and his M.S. in Electronics from St. Petersburg State Electrical Engineering Institute, Russia.  Dr. Nikishin has served as a Doctoral Student Advisor and Supervisor, Master Student Advisor and Supervisor, Undergrad Projects Lab Advisor, as well as serving on numerous committees.  

Abstact: We report a significant improvement in the room temperature cathodoluminescence efficiency of AlGaN quantum wells when the three-dimensional growth mode is induced by reduced flux of ammonia. We interpret this observation in terms of formation of quantum dots of AlGaN in Al0.45Ga0.55N wells. Reflection high electron diffraction images and detailed measurements of the cathodoluminescence intensity, linewidth, and wavelength as a function of growth conditions are consistent with the presence of quantum dots.

"Digital Alloys of AlN/AlGaN for Deep UV Light Emitting Diodes"

Sergey Nikishin, Associate Professor in Electrical and Computer Engineering

Abstact: We report a systematic study of the optical and electrical properties of deep ultraviolet light emitting diodes based on digital alloy structures of AlN/Al0.08Ga0.92N grown by gas source molecular beam epitaxy with ammonia. Digital alloys are formed by short period superlattices consisting of Al0.08Ga0.92N wells, 0.50 or 0.75 nm thick, and AlN barriers, 0.75 to 1.5 nm thick. For digital alloys with effective bandgap of 5.1 eV, average AlN composition 72%, we obtain room temperature electron concentrations up to 1× 1019 cm-3 and resistivity of 0.005 Ω·cm and hole concentrations of 1× 1018 cm-3 with resistivity of 6 Ω·cm. Light emitting diodes based on digital alloys are demonstrated operating in the range of 250 to 290 nm.

"Metal-organic Molecular-beam Epitaxy of GaN with Trimethylgallium and Ammonia: Experiment and Modeling"

Sergey Nikishin, Associate Professor in Electrical and Computer Engineering

Abstact: Metal-organic molecular-beam epitaxy with trimethylgallium and ammonia is used to grow GaN on Si(111). Our analysis of the growth data shows an increase in the apparent formation energy Eapp of epitaxial GaN, from 0.168 to  0.56  eV, with an increasing flux of ammonia. A rate-equation-based growth model is proposed and used to fit the growth data. Regarding the interaction potential, the model assumes the presence of an activated state, intermediate between physisorption and chemisorption, and includes second-order recombination-desorption processes important in the modeling of high-temperature growth. It is shown that the formation energy of epitaxial GaN, Ef, depends on the growth conditions as the activation energy and surface diffusion energy barriers increase or decrease with the change in the impinging fluxes and surface density of precursors. For such a particular set of growth conditions, the model allows us to determine the formation energy of epitaxial GaN as Ef=0.11  eV, ~35% smaller than the apparent activation energy obtained directly from the growth data. Eapp=0.168  eV.

"Effect of Nanocomposite Synthesis on the Combustion Performance of a Ternary Thermite"

Michelle Pantoya, Associate Professor in Mechanical Engineering

Bio: Dr. Michelle Pantoya is a professor in the Department of Mechanical Engineering.  Dr. Pantoya earned her Ph.D. in Mechanical Engineering, M.S. in Mechanical Engineering, and B.S. in Aeronautical Engineering, from University of California, Davis.  Dr. Pantoya’s teaching areas are: heat transfer, fluid mechanics, thermodynamics, and combustion.  Research interests include: energetic materials, combustion, experimental heat transfer and wind tunnel modeling.

Abstact: Nanocomposite thermites are attractive materials for their diverse applications from metallurgy to ordnance technologies. While there are a plethora of combinations of fuel and oxidizers, this work shows that the composite's overall performance is intimately tied to how the fuel and oxidizer are prepared and combined. Comparison of the combustion velocities of two separate ternary mixtures of Al-Fe2O3-SiO2, one prepared in situ using sol-gel processing and the other prepared by physically mixing discrete nanoscale particles, demonstrated different burning behaviors as a result of preparation technique. The stoichiometry of the two sets of thermite was varied to examine the influence of SiO2 on combustion velocity as a means to control the reaction behavior. For pure Fe2O3 + Al reactions, results show that the sol-gel synthesized materials (40 m/s) exhibit increased velocities over the physically mixed materials (9 m/s) by approximately 4 times. This trend is not observed, however, upon addition of SiO2 to the thermite mixture; ternary thermites with 40 wt % SiO2 showed decreased burn velocities of 0.02 m/s for sol-gel prepared thermites compared to 0.2 m/s for their physically mixed counterparts. The observed trends are believed to be caused by the unique mixing between the Fe2O3 and SiO2 phases resulting from the two synthesis techniques.

"Transboundary Impacts on Regional Ground Water Modeling in Texas"

Ken Rainwater, Professor in Engineering and Director, Water Resource Center

Bio: Dr. Ken Rainwater joined the TTU faculty in 1985. His expertise includes areas such as environmental contamination and water rights, groundwater well field design, and groundwater modeling and risk assessment.

Abstact: Recent legislation required regional grassroots water resources planning across the entire state of Texas. The Texas Water Development Board (TWDB), the state's primary water resource planning agency, divided the state into 16 planning regions. Each planning group developed plans to manage both ground water and surface water sources and to meet future demands of various combinations of domestic, agricultural, municipal, and industrial water consumers. This presentation describes the challenges in developing a ground water model for the Llano Estacado Regional Water Planning Group (LERWPG), whose region includes 21 counties in the Southern High Plains of Texas. While surface water is supplied to several cities in this region, the vast majority of the regional water use comes from the High Plains aquifer system, often locally referred to as the Ogallala Aquifer. Over 95% of the ground water demand is for irrigated agriculture. The LERWPG had to predict the impact of future TWDB-projected water demands, as provided by the TWDB, on the aquifer for the period 2000 to 2050. If detrimental impacts were noted, alternative management strategies must be proposed. While much effort was spent on evaluating the current status of the ground water reserves, an appropriate numerical model of the aquifer system was necessary to demonstrate future impacts of the predicted withdrawals as well as the effects of the alternative strategies. The modeling effort was completed in the summer of 2000. This presentation concentrates on the political, scientific, and nontechnical issues in this planning process that complicated the modeling effort. Uncertainties in data, most significantly in distribution and intensity of recharge and withdrawals, significantly impacted the calibration and predictive modeling efforts. Four predictive scenarios, including baseline projections, recurrence of the drought of record, precipitation enhancement, and reduced irrigation demand, were simulated to identify counties at risk of low final ground water storage volume or low levels of satisfied demand by 2050. Copyright © 2005 National Ground Water Association. (15 refs.)

"Perchlorate occurrence in the Texas southern high plains aquifer system"

Ken Rainwater, Professor in Engineering and Director, Water Resource Center

Abstact: Recent legislation required regional grassroots water resources planning across the entire state of Texas. This presentation describes the challenges in developing a ground water model for the Llano Estacado Regional Water Planning Group, whose region includes 21 counties in the Southern High Plains of Texas. Four predictive scenarios, including baseline projections, recurrence of the drought of record, precipitation enhancement, and reduced irrigation demand, were simulated to identify counties at risk of low final ground water storage volume or low levels of satisfied demand by 2050.

"Variability of Residual Stresses and Superposition Effect in Multipass Grinding of High-Carbon High-Chromium Steel"

Iris Rivero, Assistant Professor in Industrial Engineering

Bio: Iris V. Rivero is an Assistant Professor of Industrial Engineering at Texas Tech University. She received a B.S., M.S., and Ph.D. in Industrial and Manufacturing Engineering from the Pennsylvania State University. She has industrial experience in the field of advanced manufacturing systems and materials at Detroit Diesel Corporation and Honeywell Engines & Systems. In addition, she has worked on funded projects from NASA and DOE. Her research interests include manufacturing processes, materials, and nondestructive testing.

Abstact: Residual stresses (RS) and surface integrity of D2-steel generated from heat treatment and multipass grinding was investigated. The causality of the RS was explained through the strong correlation of surface integrity characteristics and RS patterns. The main sources of variation were the RS distribution depth and multipass grinding technique. Grinding effect on RS was statistically significant; however, it was mostly predetermined by the pre-existing RS induced during heat treatment. Regardless of preceding treatments, the effect of multipass grinding technique exhibited similar RS patterns, which suggests existence of the superposition relationship and orthogonal memory between the passes of the grinding operation.

"Nonaxisymmetric Effects of Stratified Spin-up in an Axisymmetric Annular Channel"

Sergey Smirnov, Assistant Professor in Mechanical Engineering

Bio: Dr. Smirnov holds degrees from Arizona State University, Moscow Physical-Engineering Institute, and the Institute of Problems in Mechanics, (USSR). His research interests include rotating & straified flows and Turbulence & mixing.

Abstact: Laboratory experiments were conducted on spin-up of a linearly stratifed fluid in a rotating axisymmetric annular channel formed by two cylindrical coaxial walls and a flat bottom.<.font>

"International Edition of Incident at Morales: An Engineering Ethics Story"

Jimmy Smith, Professor in Civil Engineering and Director, National Institute for Engineering Ethics, Murdough Center for Engineering Professionalism

Bio: Dr. Smith holds degrees from Texas Tech University and the University of Arizona.  He holds the title of Fellow in the National Society of Professional Engineers and the American Society of Civil Engineers.  A member of the faculty at Texas Tech since 1971, Professor Smith has been promoting engineering ethics projects and programs since 1988.  He has developed and offered over 300 workshops, seminars, and invited presentations in engineering ethics throughout the United States as well as Russia, Japan, Malaysia, Mexico, and Canada.

Abstact: The DVD movie "International Edition of Incident at Morales " 2005, subtitled in 13 languages. is a 36-minute dramatic case study which emphasizes the responsibilities of engineers and the resulting benefit to the public. Cast in an international context, the movie was created by a team of engineers and philosophers from five universities and three companies and dramatizes a fictional but realistic case study in engineering ethics. Funding to create this educational movie was provided by a major grant to Texas Tech University from the US National Science Foundation (NSF SES-0138309) and donations from engineering societies, firms and individuals.

"Wind and Water: Redeveloping Regional Resources for the New Economy"

Andrew H. P. "Andy " Swift, Professor in Civil Engineering and Director, Wind Science and Engineering Research Center

Bio: Andrew H. P. Swift, Jr., is a professor in Civil Engineering and the Director for the Wind Science and Engineering Center (WISE).  Dr. Swift received his D.Sc. in Mechanical Engineering and M.S. in Mechanical Engineering from Washington University.  He received his B. S. in Mathematics and his B. S. in Mechanical Engineering from Union College.  Some of the undergraduate courses taught by Dr. Swift are: Mechanics (Newtonian dynamics), Thermodynamics, Fundamentals of Digital Computation, and Engineering Analysis (numerical methods).  Dr. Swift has participated in numerous funded research activities, with his awards from 1981 to the present totaling $14 million.

Abstact:

"Digital Alloys of AlN/AlGaN for Deep UV Light Emitting Diodes"

Henryk Temkin, Horn and Maddox Professor in Electrical Engineering

Bio:

Abstact:

"Enhanced Deep Ultraviolet Luminescence from AlGaN Quantum Wells Grown in the Three-dimensional Mode"

Henryk Temkin, Horn and Maddox Professor in Electrical Engineering

Abstact: We report a significant improvement in the room temperature cathodoluminescence efficiency of AlGaN quantum wells when the three-dimensional growth mode is induced by reduced flux of ammonia. We interpret this observation in terms of formation of quantum dots of AlGaN in Al0.45 Ga0.55 N wells. Reflection high electron diffraction images and detailed measurements of the cathodoluminescence intensity, linewidth, and wavelength as a function of growth conditions are consistent with the presence of quantum dots. © 2005 American Institute of Physics. (21 refs.)

"Metal-organic Molecular-beam Epitaxy of GaN with Trimethylgallium and Ammonia: Experiment and Modeling"

Henryk Temkin, Horn and Maddox Professor in Electrical Engineering

Abstact: Metal-organic molecular-beam epitaxy with trimethylgallium and ammonia is used to grow GaN on Si(111). Our analysis of the growth data shows an increase in the apparent formation energy Eapp of epitaxial GaN, from 0.168 to 0.56 eV, with an increasing flux of ammonia. A rate-equation-based growth model is proposed and used to fit the growth data. Regarding the interaction potential, the model assumes the presence of an activated state, intermediate between physisorption and chemisorption, and includes second-order recombination-desorption processes important in the modeling of high-temperature growth. It is shown that the formation energy of epitaxial GaN, Ef, depends on the growth conditions as the activation energy and surface diffusion energy barriers increase or decrease with the change in the impinging fluxes and surface density of precursors. For such a particular set of growth conditions, the model allows us to determine the formation energy of epitaxial GaN as Ef =0.11 eV, [similar to] 35% smaller than the apparent activation energy obtained directly from the growth data. Eapp =0.168 eV. © 2005 American Institute of Physics. (20 refs.)

"The Origin of Naturally Occurring Perchlorate: The Role of Atmospheric Processes"

Richard W. Tock, Adjunct Professor in Chemical Engineering

Bio:

Abstact: Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largely to the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (~0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. We report that perchlorate is present in many rain and snow samples. This strongly suggests that some perchlorate is formed in the atmosphere and a natural perchlorate background of atmospheric origin should exist.

"Perchlorate Occurrence in the Texas Southern High Plains Aquifer System"

Richard W. Tock, Adjunct Professor in Chemical Engineering

Abstact: In the spring of 2002, the Texas Commission on Environmental Quality determined that perchlorate (ClO4-) was present in the ground water from the McMillan and Paul Davis well fields that supply potable water for the city of Midland. Researchers began a large-scale sampling program to determine the source(s) and distribution of perchlorate in the area’s ground water. This document summarizes the findings of a large-scale investigation in nine counties carried out from July to December 2002. This program included public water systems (PWS) wells and private wells in Andrews, Borden, Dawson, Ector, Gaines, Glasscock, Howard, Martin, and Midland counties, which occupy a total area of 23,960 km2. Water samples were tested for perchlorate and a suite of common ions. From a total of 254 wells sampled in nine counties, 179 wells (70%) had detectable perchlorate concentrations (>0.5 ppb) and 88 wells (35%) had perchlorate concentrations equal to or above 4 ppb. The highest perchlorate concentration found at a private well was 58.8 ppb in Dawson County, while the highest concentration detected for a well in PWS was 45.6 ppb in city of Midland, Midland County. Perchlorate positively correlated (α < 0.0001) with Cl-, F-, Br-, SO42-, Mg2+, and K+ but not with NO2-, NO3-, NA+, or Ca+. Research to date has identified the most likely sources to be (1) a natural mineralogical impurity; (2) agricultural fertilizers containing perchlorate; (3) in situ generation of perchlorate by electrochemical reactions; or (4) some combination of the three. This study suggests that there may be significant sources other than the traditional industrial processing of perchlorate, and the distribution of perchlorate in ground water is likely more widespread than previously suspected.