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 Spectroscopic ellipsometry (2)
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 Direct numerical simulations (2)
 Semiconducting indium compounds (2)
 Thin films (2)
 2D domain decomposition (2)
 Velocity gradients (2)
 Parallel implementation (2)
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 Cast materials (1)
 Bernoulli equations (1)
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 Conservation of momentum (1)
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 Contact resistance (1)
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Articles 1  19 of 19
FullText Articles in Engineering Science and Materials
CurrentDriven Production Of VortexAntivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In LongRange Order, Francisco EstellésDuart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich
CurrentDriven Production Of VortexAntivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In LongRange Order, Francisco EstellésDuart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich
Physics Faculty Publications
Proliferation of topological defects like vortices and dislocations plays a key role in the physics of systems with longrange order, particularly, superconductivity and superfluidity in thin films, plasticity of solids, and melting of atomic monolayers. Topological defects are characterized by their topological charge reflecting fundamental symmetries and conservation laws of the system. Conservation of topological charge manifests itself in extreme stability of static topological defects because destruction of a single defect requires overcoming a huge energy barrier proportional to the system size. However, the stability of driven topological defects remains largely unexplored. Here we address this issue and investigate numerically ...
Preface To Special Topic: A Tribute To John Lumley, Kiran Bhaganagar, Thomas B. Gatski, William K. George
Preface To Special Topic: A Tribute To John Lumley, Kiran Bhaganagar, Thomas B. Gatski, William K. George
CCPO Publications
This Special Topic Section is dedicated to the life and memory of John Leask Lumley(19302015), professor and scientist extraordinaire.
Comment On "Roles Of Bulk Viscosity On RayleighTaylor Instability: NonEquilibrium Thermodynamics Due To SpatioTemporal Pressure Fronts" Phys. Fluids 28, 094102 (2016), Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
No abstract provided.
Effects Of Gravity On The Acceleration And Pair Statistics Of Inertial Particles In Homogeneous Isotropic Turbulence, H. Parishani, O. Ayala, B. Rosa, L.P. Wang, W. W. Grabowski
Effects Of Gravity On The Acceleration And Pair Statistics Of Inertial Particles In Homogeneous Isotropic Turbulence, H. Parishani, O. Ayala, B. Rosa, L.P. Wang, W. W. Grabowski
Engineering Technology Faculty Publications
Within the context of heavy particles suspended in a turbulent airflow, we study the effects of gravity on acceleration statistics and radial relative velocity (RRV) of inertial particles. The turbulent flow is simulated by direct numerical simulation (DNS) on a 256^{3} grid and the dynamics of O(10^{6}) inertial particles by the pointparticle approach. For particles/droplets with radius from 10 to 60 µm, we found that the gravity plays an important role in particle acceleration statistics: (a) a peak value of particle acceleration variance appears in both the horizontal and vertical directions at a particle Stokes number ...
Effects Of Forcing Time Scale On The Simulated Turbulent Flows And Turbulent Collision Statistics Of Inertial Particles, B. Rosa, H. Parishani, O. Ayala, L.P. Wang
Effects Of Forcing Time Scale On The Simulated Turbulent Flows And Turbulent Collision Statistics Of Inertial Particles, B. Rosa, H. Parishani, O. Ayala, L.P. Wang
Engineering Technology Faculty Publications
In this paper, we study systematically the effects of forcing time scale in the largescale stochastic forcing scheme of Eswaran and Pope ["An examination of forcing in direct numerical simulations of turbulence," Comput. Fluids 16, 257 (1988)] on the simulated flow structures and statistics of forced turbulence. Using direct numerical simulations, we find that the forcing time scale affects the flow dissipation rate and flow Reynolds number. Other flow statistics can be predicted using the altered flow dissipation rate and flow Reynolds number, except when the forcing time scale is made unrealistically large to yield a Taylor microscale flow Reynolds ...
NonEquilibrium Pressure Control Of The Height Of A LargeScale, GroundCoupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan
NonEquilibrium Pressure Control Of The Height Of A LargeScale, GroundCoupled, Rotating Fluid Column, R. L. Ash, I. R. Zardadhkan
Mechanical & Aerospace Engineering Faculty Publications
When a groundcoupled, rotating fluid column is modeled incorporating nonequilibrium pressure forces in the NavierStokes equations, a new exact solution results. The solution has been obtained in a similar manner to the classical equilibrium solution. Unlike the infiniteheight, classical solution, the nonequilibrium pressure solution yields a groundcoupled rotating fluid column of finite height. A viscous, nonequilibrium Rankine vortex velocity distribution, developed previously, was used to demonstrate how the viscous and nonequilibrium pressure gradient forces, arising in the vicinity of the velocity gradient discontinuity that is present in the classical Rankine vortex model, effectively isolate the rotating central fluid column from ...
Optical Detection Of Melting Point Depression For Silver Nanoparticles Via In Situ Real Time Spectroscopic Ellipsometry, S. A. Little, T. Begou, R. W. Collins, S. Marsillac
Optical Detection Of Melting Point Depression For Silver Nanoparticles Via In Situ Real Time Spectroscopic Ellipsometry, S. A. Little, T. Begou, R. W. Collins, S. Marsillac
Electrical & Computer Engineering Faculty Publications
Silver nanoparticle films were deposited by sputtering at room temperature and were annealed while monitoring by real time spectroscopic ellipsometry (SE). The nanoparticle dielectric functions (0.75 eV6.5 eV) obtained by SE were modeled using Lorentz and generalized oscillators for the nanoparticle plasmon polariton (NPP) and interband transitions, respectively. The nanoparticle melting point could be identified from variations in the oscillator parameters during annealing, and this identification was further confirmed after cooling through significant, irreversible changes in these parameters relative to the asdeposited film. The variation in melting point with physical thickness, and thus average nanoparticle diameter, as measured ...
The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar
The Influence Of Pressure Relaxation On The Structure Of An Axial Vortex, Robert L. Ash, Irfan Zardadkhan, Allan J. Zuckerwar
Mechanical & Aerospace Engineering Faculty Publications
Governing equations including the effects of pressure relaxation have been utilized to study an incompressible, steadystate viscous axial vortex with specified farfield circulation. When sound generation is attributed to a velocity gradient tensorpressure gradient product, the modified conservation of momentum equations that result yield an exact solution for a steady, incompressible axial vortex. The vortex velocity profile has been shown to closely approximate experimental vortex measurements in air and water over a wide range of circulationbased Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and ...
Volume Viscosity In Fluids With Multiple Dissipative Processes, Allan J. Zuckerwar, Robert L. Ash
Volume Viscosity In Fluids With Multiple Dissipative Processes, Allan J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
The variational principle of Hamilton is applied to derive the volume viscosity coefficients of a reacting fluid with multiple dissipative processes. The procedure, as in the case of a single dissipative process, yields two dissipative terms in the NavierStokes equation: The first is the traditional volume viscosity term, proportional to the dilatational component of the velocity; the second term is proportional to the material time derivative of the pressure gradient. Each dissipative process is assumed to be independent of the others. In a fluid comprising a single constituent with multiple relaxation processes, the relaxation times of the multiple processes are ...
Electronic And Structural Properties Of Molybdenum Thin Films As Determined By Real Time Spectroscopic Ellipsometry, J. D. Walker, H. Khatri, V. Ranjan, Jian Li, R. W. Collins, S. Marsillac
Electronic And Structural Properties Of Molybdenum Thin Films As Determined By Real Time Spectroscopic Ellipsometry, J. D. Walker, H. Khatri, V. Ranjan, Jian Li, R. W. Collins, S. Marsillac
Electrical & Computer Engineering Faculty Publications
Walker, J.D., Khatri, H., Ranjan, V., Li, J., Collins, R.W., & Marsillac, S. (2009). Electronic and structural properties of molybdenum thin films as determined by realtime spectroscopic ellipsometry. Applied Physics Letters, 94(14). doi: 10.1063/1.3117222
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones, Kursat Kara
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones, Kursat Kara
Mechanical & Aerospace Engineering Theses & Dissertations
The receptivity mechanisms of hypersonic boundary layers to free stream acoustic disturbances are studied using both linear stability theory (LST) and direct numerical simulations (DNS). A computational code is developed for numerical simulation of steady and unsteady hypersonic flow over cones by combining a fifthorder weighted essentially nonoscillatory (WENO) scheme with thirdorder totalvariationdiminishing (TVD) RungeKutta method. Hypersonic boundary layer receptivity to freestream acoustic disturbances in slow and fast modes over 5degree, halfangle blunt cones and wedges are numerically investigated. The freestream Mach number is 6.0, and the unit Reynolds number is 7.8×106/ft. Both the steady and ...
Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash
Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
The variational principle of Hamilton is applied to develop an analytical formulation to describe the volume viscosity in fluids. The procedure described here differs from those used in the past in that a dissipative process is represented by the chemical affinity and progress variable (sometimes called "order parameter") of a reacting species. These state variables appear in the variational integral in two places: first, in the expression for the internal energy, and second, in a subsidiary condition accounting for the conservation of the reacting species. As a result of the variational procedure, two dissipative terms appear in the NavierStokes equation ...
Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash
Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
We respond to the Comment of Markus Scholle and therewith revise our material entropy constraint to account for the production of entropy. (c) 2006 American Institute of Physics.
Evolution Of The Band Structure Of ΒIn2 S3−3x O3x Buffer Layer With Its Oxygen Content, N. Barreau, S. Marsillac, J. C. Bernède, L. Assmann
Evolution Of The Band Structure Of ΒIn2 S3−3x O3x Buffer Layer With Its Oxygen Content, N. Barreau, S. Marsillac, J. C. Bernède, L. Assmann
Electrical & Computer Engineering Faculty Publications
The evolution of the band structure of βIn2 S3−3x O3x (BISO) thin films grown by physical vapor deposition, with composition x, is investigated using xray photoelectron spectroscopy. It is shown that the energy difference between the valenceband level and the Fermi level remains nearly constant as the optical band gap of the films increases. As a consequence, the difference between the conduction band level and the Fermi level increases as much as the optical band gap of the films. The calculation of the electronic affinity [ ] of the BISO thin films shows that it decreases linearly from 4.65 to ...
Study Of A Growth Instability Of ΓIn[Sub 2]Se[Sub 3], C. Amory, J. C. Bernede, S. Marsillac
Study Of A Growth Instability Of ΓIn[Sub 2]Se[Sub 3], C. Amory, J. C. Bernede, S. Marsillac
Electrical & Computer Engineering Faculty Publications
γIn[sub 2]Se[sub 3] thin film are deposited for various substrate temperatures in the range of 523–673 K. This study shows that at 573 and 673 K the thin films are well crystallized with grains aligned along the c axis. Between these temperatures, a domain of instability appears where the γIn[sub 2]Se[sub 3] thin films have a randomly orientation and the clattice parameter increases. The presence of the metastable phase κIn[sub 2]Se[sub 3], during the growth, can explain the existence of this domain of instability. The insertion of Zn during the ...
Textured Mos 2 Thin Films Obtained On Tungsten: Electrical Properties Of The W/Mos 2 Contact, E. Gourmelon, J. C. Bernède, J. Pouzet, S. Marsillac
Textured Mos 2 Thin Films Obtained On Tungsten: Electrical Properties Of The W/Mos 2 Contact, E. Gourmelon, J. C. Bernède, J. Pouzet, S. Marsillac
Electrical & Computer Engineering Faculty Publications
Textured films of molybdenum disulfide have been obtained by solid state reaction between the constituents in thin films form when a (200) oriented tungsten sheet is used as substrate. The crystallites have their c axis perpendicular to the plane of the substrate. The annealing conditions are T=1073K and t=30 min. The films are stoichoimetric and p type. Such highly textured films are achieved without foreign atom addition (Ni, Co...). It appears, as shown by xray photoelectron spectroscopy, that a thin WS_{2} layer is present at the interface W/MoS_{2}. The crystallization process is discussed by a ...
Efficient Dynamic Unstructured Methods And Applications For Transonic Flows And Hypersonic Stage Separation, Xiaobing Luo
Efficient Dynamic Unstructured Methods And Applications For Transonic Flows And Hypersonic Stage Separation, Xiaobing Luo
Mechanical & Aerospace Engineering Theses & Dissertations
Relativemoving boundary problems have a wide variety of applications. They appear in staging during a launch process, store separation from a military aircraft, rotorstator interaction in turbomachinery, and dynamic aeroelasticity.
The dynamic unstructured technology (DUT) is potentially a strong approach to simulate unsteady flows around relativemoving bodies, by solving timedependent governing equations. The dualtime stepping scheme is implemented to improve its efficiency while not compromising the accuracy of solutions. The validation of the implicit scheme is performed on a pitching NACA0012 airfoil and a rectangular wing with low reduced frequencies in transonic flows. All the matured accelerating techniques, including the ...
An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash
An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
A steadystate apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics
Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash
Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash
Mechanical & Aerospace Engineering Faculty Publications
A critical analysis of available compliant wall data which indicated drag reduction under turbulent boundary layers is presented. Detailed structural dynamic calculations suggest that the surfaces responded in a resonant, rather than a compliant, manner. Alternate explanations are given for drag reductions observed in two classes of experiments: (1) flexible pipe flows and (2) waterbacked membranes in air. Analysis indicates that the wall motion for the remaining data is typified by short wavelengths in agreement with the requirements of a possible compliant wall drag reduction mechanism recently suggested by Langley. Copyright © 1977 American Institute of Physics.