22nd Annual Faculty Academic Contributions Virtual Exhibit |
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The following items, arranged by the author's last name, were part of the 2006 exhibit:
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.
Xinzhong Chen, Assistant Professor in Civil Engineering
Xinzhong Chen, Assistant Professor in Civil Engineering
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
Javad Hashemi, Professor in Mechanical Engineering Abstact:
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.
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. 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.
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.
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.
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.
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:
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.
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.
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 "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.
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.
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.)
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.
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.
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.
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.)
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.
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. |
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University Library
FACE 2006
2006 Entries- Engineering
"Coupled Dynamic Analysis and Equivalent
Static Wind Loads on Buildings with Three-Dimensional Modes"
"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
"Transformation-Induced Plasticity and
Cascading Structural Changes in Hexagonal Boron Nitride Under High Pressure
and Shear," Applied Physics Letters, 86
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
"Application of a Dialysis Sampler to
Monitor Phytoremediation Processes," Environmental Monitoring and
Assessment, vol. 107 (2005): 155-171
"Balsa Wood Plate-Type Model used in
Research"
"Transformation-Induced Plasticity and
Cascading Structural Changes in Hexagonal Boron Nitride Under High Pressure
and Shear," Applied Physics Letters, 86
"Effect of Nanocomposite Synthesis on
the Combustion Performance of a Ternary Thermite"
"Transboundary Impacts on Regional
Ground Water Modeling in Texas"
"Variability of Residual Stresses and
Superposition Effect in Multipass Grinding of High-Carbon High-Chromium
Steel"
"Nonaxisymmetric Effects of Stratified
Spin-up in an Axisymmetric Annular Channel"
"Wind and Water: Redeveloping Regional
Resources for the New Economy"
"The Origin of Naturally Occurring
Perchlorate: The Role of Atmospheric Processes"