Digital Commons Network^™

Alloy Recovery And Control In Steel Melting, Kent D. Peaslee, Darryl S. Webber, Semen Naumovich Lekakh, Bradley Randall

Materials Science and Engineering Faculty Research & Creative Works

Alloy recovery plays an important role in steel melting economics because the cost of alloying additives such as ferroalloys and pure non-ferrous metals is significantly higher than the cost of steel scrap. Recovery of alloying additives also influences the reproducibility of steel properties from heat to heat. This paper reviews alloy recovery and final chemistry distributions at seven steel foundries and preliminary laboratory studies of alloy dissolution in ladles. Melting and alloy practices were observed for several plant trial heats in each of the foundries. Alloying and chemistry data were collected for an additional 20 - 155 heats at each …

Efficiency In Steel Melting: Ladle Development, Kent D. Peaslee, Semen Naumovich Lekakh, Todd P. Sander, Jeffrey D. Smith

Materials Science and Engineering Faculty Research & Creative Works

Effective ladle design and use is important for steel casting production. In foundry operations, the ladle temperature of the liquid steel is typically 150 to 250°F above the steel's melting point to compensate for the heat losses in small ladles and the associated high cooling rates from the large surface area to volume ratios. Higher superheat is also necessary to provide sufficient steel fluidity to properly fill the mold cavity. In spite of the relatively short time that the steel is in contact with the ladle lining, the huge thermal gradients in the lining drive high values of heat flow …

Efficiency In Steel Melting: Opportunities And Progress, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Jay Triplett

Materials Science and Engineering Faculty Research & Creative Works

This paper summarizes the findings from a study of melting efficiency in steel foundries and provides examples of material and energy savings from improvements in technology and melting practices. This study is based on information gathered at 19 Steel Founders Society of America member foundries and includes a combination of historical data and industrial measurements by the research team. Information and data were collected on the type of melting equipment, melting practices, energy use and ladle practices. The data was statistically analyzed using STATGRAPHICS commercial software. A multiple regression analysis allowed evaluation of the influence of the melting furnace (type, …

Elevated Temperature Deformation Behavior Of Nanostructured Al-Ni-Gd-Fe Alloys, X. L. Shi, Rajiv S. Mishra, T. J. Watson

Materials Science and Engineering Faculty Research & Creative Works

The elevated temperature deformation behavior of nanostructured Al89Ni3Gd7Fe1 alloy was characterized. Tensile strength was 760 MPa at 373 K. Ductility of the alloy increases with increasing strain rate at 573 K. At high temperatures (623-673 K), the operative deformation mechanism is dislocation-climb controlled.

Structure, Magnetic, And Transport Properties Of Ti-Substituted La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William Joseph James, William B. Yelon, D. Buddhikot, Satish K. Malik, Paul Ernest Parris

Materials Science and Engineering Faculty Research & Creative Works

Ti-substituted perovskites La_0.7Sr_0.3Mn_1-xTi_xO₃ with 0 ≤ x ≤ 0.20, were investigated by neutron diffraction, magnetization, electric resistivity, and magnetoresistance (MR) measurements. All samples show a rhombohedral structure (space group R3c) from 10 K to room temperature. At room temperature, the cell parameters a,c and the unit cell volume increase with increasing Ti content. However, at 10 K, the cell parameter a has a maximum value for x = 0.10, and decreases for x > 0.10, while the unit cell volume remains nearly constant for x > 0.10. The average (Mn,Ti)-O bond length increases …

A Methodology For Model Selection In Engineering Design, Rajesh Radhakrishnan, Daniel A. Mcadams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Engineering design consists of a series of stages during which a number of decisions need to be made by the designer. Since the information available to the designer is limited during initial design stages, to make these decisions and be able to proceed further in the design process, the designer needs to depict the nature, visualize the form, and predict the behavior of the product through the use of aids called models. These models guide these decisions; therefore, the designer needs to ensure the downstream validity of these decisions by constructing models with sufficient accuracy and resolution. Because higher quality …

Multiple Spacecraft Formation Control Using Θ - D Method, Ming Xin, S. N. Balakrishnan, Henry J. Pernicka

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multiple spacecraft formation control about the L2 libration point is investigated in this paper. the circular restricted three-body problem with Sun and Earth as the two primaries is utilized as a framework of study. the idea of virtual structure is considered as the architecture of multiple spacecraft formation. the center of the virtual rigid body follows a nominal orbit around the L2 libration point. the individual spacecraft is controlled so as to keep a constant relative distance from the center of the virtual structure. a nonlinear model is developed that describes the relative formation dynamics. This nonlinear control problem was …

Dynamic Re-Optimization Of A Mems Controller In Presence Of Unmodeled Uncertainties, Nishant Unnikrishnan, S. N. Balakrishnan, Venkat Durbha

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Online trained neural networks have become popular in recent years in designing robust and adaptive controllers for dynamic systems with uncertainties in their system equations because of their universal function approximation property. This paper discusses a technique that dynamically reoptimizes a Single Network Adaptive Critic (SNAC) based optimal controller in the presence of unmodeled uncertainties. The controller design is carried out in two steps: (i) synthesis of a set of online neural networks that capture the uncertainties in the plant equations on-line (ii) re-optimization of the existing optimal controller to drive the states of the plant to a desired reference …

A Model Of Function-Based Representations, Michael Van Wie, Cari R. Bryant, Matt R. Bohm, Robert B. Stone, Daniel A. Mcadams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The need to model and to reason about design alternatives throughout the design process demands robust representation schemes of function, behavior, and structure. Function describes the physical effect imposed on an energy or material flow by a design entity without regard for the working principles or physical solutions used to accomplish this effect. Behaviors are the physical events associated with a physical artifact (or hypothesized concept) over time (or simulated time) as perceived by an observer. Structure, the most tangible concept, partitions an artifact into meaningful constituents such as features, Wirk elements, and interfaces in addition to the widely used …

Experimental Verification Of Near-Wall Hindered Diffusion Theory For The Brownian Motion Of Nanoparticles Using Evanescent Wave Microscopy, Kenneth D. Kihm, Arindam Banerjee

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A total internal reflection fluorescence microscopy technique coupled with three-dimensional tracking of nanoparticles is used to experimentally verify the theory on near-wall hindered Brownian motion [Goldman et al., Chem. Eng. Sci. 22, 637 (1967); Brenner, Chem. Eng. Sci. 16, 242 (1967)] very close to the solid surface (within ~1 µm). The measured mean square displacements (MSDs) in the lateral x-y directions show good agreement with the theory for all tested nanoparticles of radii 50, 100, 250, and 500 nm. However, the measured MSDs in the z direction deviate substantially from the theory particularly for the case of smaller particles of …

Grouping Www Image Search Results By Novel Inhomogeneous Clustering Method, Gu Xu, Zhiwei Li, Mingjing Li, Wei-Ying Ma, Hong-Jiang Zhang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a novel inhomogeneous clustering method is proposed for grouping web images. It is used to re-organize the search result of web image search engines into a hierarchical structure so that the users can conveniently browse the search result. This method takes into account various features associated with web images, and treats them in different ways. For the surrounding text extracted from the containing web pages, co-clustering approach is adopted; for low-level features of the image content and other features, one-way clustering approach is adopted. The clustering results of different approaches are combined together to produce the final …

Hierarchical Optimal Force-Position Control Of A Turning Process, B. Pandurangan, Robert G. Landers, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Machining process control technologies are currently not well integrated into machine tool controllers and, thus, servomechanism dynamics are often ignored when designing and implementing process controllers. In this brief, a hierarchical controller is developed that simultaneously regulates the servomechanism motions and cutting forces in a turning operation. The force process and servomechanism system are separated into high and low levels, respectively, in the hierarchy. The high-level goal is to maintain a constant cutting force to maximize productivity while not violating a spindle power constraint. This goal is systematically propagated to the lower level and combined with the low-level goal to …

Optimal And Hierarchical Formation Control For Uav, Xiaohua Wang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, optimal and hierarchical control concepts are investigated for cooperative formation flying of aircrafts. The airplanes are modeled as point mass and represented by double integrators. And all the planes are considered to be in a plane. For demonstration of the concepts, a task of forming a square from arbitrary initial conditions is presented to four airplanes. The final position that each airplane has to reach is unknown to them. The goal for the team is abstracted in the top layer. The system is modeled as a two layer hierarchical system in which the global information comes from …

Stochastic Optimal Control With Neural Networks And Application To A Retailer Inventory Problem, Zhongwu Huang, Xiaohua Wang, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Overwhelming computational requirements of classical dynamic programming algorithms render them inapplicable to most practical stochastic problems. To overcome this problem a neural network based Dynamic Programming (DP) approach is described in this study. The cost function which is critical in a dynamic programming formulation is approximated by a neural network according to some designed weight-update rule based on Temporal Difference(TD)learning. A Lyapunov based theory is developed to guarantee an upper error bound between the output of the cost neural network and the true cost. We illustrate this approach through a retailer inventory problem.

Performance Of A Bgo Pet/Ct With Higher Resolution Pet Detectors, John W. Wilson, Timothy G. Turkington, J. J. Williams, James G. Colsher, D. L. Mcdaniel, C. L. Kim, Steven G. Ross, C. W. Stearns, S. D. Wollenweber

Mining Engineering Faculty Research & Creative Works

A new PET detector block has been designed to replace the standard detector of the Discovery ST PET/CT system. The new detector block is the same size as the original, but consists of an 8/spl times/6 (tangential× axial) matrix of crystals rather than the original 6/spl times/6. The new crystal dimensions are 4.7× 6.3× 30 mm/sup 3/ (tangential× axial× radial). Full PET/CT systems have been built with these detectors (Discovery STE). Most other aspects of the system are identical to the standard Discovery ST, with differences including the low energy threshold for 3D imaging (now 425 keV) and front-end electronics. …

Image Quality Vs. Nec In 2d And 3d Pet, John W. Wilson, Timothy G. Turkington, Josh M. Wilson, James G. Colsher, Steven G. Ross

Mining Engineering Faculty Research & Creative Works

To investigate the relationship between NEC and image quality to 2D and 3D PET, while simultaneously optimizing 3D low energy threshold (LET), we have performed a series of phantom measurements. The phantom consisted of 46 1 cm fillable hollow spheres on a random grid inside a water-filled oval cylinder, 21 cm tall, 36 cm wide, and 40 cm long. The phantom was imaged on a Discovery ST PET/CT system (GE Healthcare, Milwaukee, WI) in a series of 3 min scans as it decayed from an activity of 7.2 mCi. The scans included LET settings of 375,400, and 425 keV in …

Investigating The Optimum Lower Energy Threshold Of A New Research Pet/Ct Scanner, Osama Mawlawi, John W. Wilson, Tinsu Pan, Timothy G. Turkington

Mining Engineering Faculty Research & Creative Works

An investigation of the optimum 3D lower energy threshold (LET) setting of the Discovery-RX, a new LYSO based GE research PET/CT scanner is conducted. Sensitivity and noise equivalent count rate (NECR) performance of the scanner in 3D mode were evaluated at multiple LET settings: 400, 425, 450, 460, 470 and 480 KeV. The performance evaluations were conducted according to the NEMA NU2-2001 standard. In addition, the NECR was also evaluated for the same LET settings using the Data Spectrum whole body phantom in order to more accurately simulate a true clinical setting. For the sensitivity measurements, the line source was …

Operation Of High-Voltage Transverse Shock Wave Ferromagnetic Generator In The Open Circuit And Charging Modes, Sergey I. Shkuratov, Evgueni F. Talantsev, Jason Baird, Larry L. Altgilbers, Allen H. Stults, Stanislav V. Kolossenok

Mining Engineering Faculty Research & Creative Works

Results of the investigation of the operation of explosive-driven high-voltage shock wave ferromagnetic generators (FMGs) in the open circuit and charging modes are presented. FMGs are based on the transverse (when the shock wave propagates across the magnetization vector M) shock demagnetization of Nd2Fe14B hard ferromagnetic energy-carrying elements of diameter 2.22 cm and length 2.54 cm (volume 8.5 cm3). In the charging mode the capacitance of capacitor banks compatt was varied from 18 to 36 nF. The energy transferred to the capacitor bank reached 0.38 J. FMGs provided pulsed powers of 35-45 kW in times ranging from 10 to 15 …

Pulsed Charging Of Capacitor Bank By Compact Explosive-Driven High-Voltage Primary Power Source Based On Longitudinal Shock Wave Depolarization Of Ferroelectric Ceramics, Sergey I. Shkuratov, Jason Baird, Evgueni F. Talantsev, Yaroslav Tkach, Larry L. Altgilbers, Allen H. Stults, Stanislav V. Kolossenok

Mining Engineering Faculty Research & Creative Works

Results of the investigation of the operation of autonomous ultracompact explosive-driven high-voltage primary power sources based on longitudinal (when the shock wave propagates along the polarization vector P0) shock wave depolarization of ferroelectric materials in the open circuit and charging modes are presented. The energy-carrying elements of shock wave ferroelectric generators (FEGs) were poled lead zirconate titanate (PZT) Pb(Zr52Ti48)O3 polycrystalline piezoelectric ceramic disks with volume 0.35 cm3. The PZT modules were shock compressed in the stress range from 1.5 to 3.8 GPa by a longitudinal shock wave generated by high explosives. In the charging mode, the FEGs provided pulsed power …

Field And Intensity Correlations In Amplifying Random Media, Alexey Yamilov, Shih-Hui Chang, Alexander Burin, Allen Taflove, Hui Cao

Physics Faculty Research & Creative Works

We study local and nonlocal correlations of light transmitted through active random media. The conventional approach results in divergence of ensemble-averaged correlation functions due to the existence of lasing realizations. We introduce a conditional average for correlation functions by omitting the divergent realizations. Our numerical simulation reveals that amplification does not affect local spatial correlation. The nonlocal intensity correlations are strongly magnified due to selective enhancement of the contributions from long propagation paths. We also show that by increasing gain, the average mode linewidth can be made comparable to the average mode spacing. This implies that light transport through a …

Near-Field Intensity Correlations In Semicontinuous Metal Films, K. Seal, H. Noh, Alexey Yamilov, A. K. Sarchev, D. A. Genov, V. M. Shalaev, Z. C. Ying, Hui Cao

Physics Faculty Research & Creative Works

Spatial intensity correlation functions of semicontinuous metal-dielectric films of varying metal concentration, p, were obtained from near-field microscopy. The data shows a transition from propagation to localization and back to propagation of optical excitations with increase in p.

Half-Metallicity And Efficient Spin Injection In Aln/Gan:Cr (0001) Heterostructure, Julia E. Medvedeva, X. Y. Cui, C. Stampfl, N. Newman, Arthur J. Freeman

Physics Faculty Research & Creative Works

First-principles investigations of the structural, electronic, and magnetic properties of Cr-doped AlN/GaN (0001) heterostructures reveal the possibility of efficient spin injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier. We demonstrate that Cr atoms segregate into the GaN region and that these interfaces retain their half-metallic behavior leading to a complete, i.e., 100%, spin polarization of the conduction electrons. This property makes the wide band-gap nitrides doped with Cr to be excellent candidates for high-efficiency magnetoelectronic devices.

Microwave Permeability Of Co₂ Z Composites, Konstantin Rozanov, Marina Koledintseva, Z. W. Li, L. F. Chen

Physics Faculty Research & Creative Works

The microwave permittivity and permeability of Co2Z barium ferrite composite samples are measured as functions of frequency and volume fraction of the ferrite. Magnetostatic properties of the bulk ferrite are determined. This allows Snoek's law [J. L. Snoek, Physica 14, 204 (1948)] to be verified by comparing the microwave and magnetostatic Snoek's constants. The modification of Snoek's law for hexagonal ferrites suggested recently by Acher et al. [Phys. Rev. B 62, 11324 (2000)] is also verified. Acher's constant is found from microwave measurements to agree with the value calculated from the magnetostatic properties of bulk ferrite, but microwave and magnetostatic …

Near-Field Intensity Correlations In Semicontinuous Metal-Dielectric Films, K. Seal, A. K. Sarychev, H. Noh, D. A. Genov, Alexey Yamilov, V. M. Shalaev, Z. C. Ying, Hui Cao

Physics Faculty Research & Creative Works

Spatial intensity correlation functions are obtained from near-field scanning optical microscope measurements of semicontinuous metal-dielectric films. The concentration of metal particles on a dielectric surface is varied over a wide range to control the scattering strength. At low and high metal coverages where scattering is weak, the intensity correlation functions exhibit oscillations in the direction of incident light due to excitation of propagating surface waves. In the intermediate regime of metal concentration, the oscillatory behavior is replaced by a monotonic decay as a result of strong scattering and anomalous absorption. Significant differences in the near-field intensity correlations between metallic and …

Role Of Embedded Clustering In Dilute Magnetic Semiconductors: Cr Doped Gan, Julia E. Medvedeva, B. Delley, N. Newman, C. Stampfl, X. Y. Cui, Arthur J. Freeman

Physics Faculty Research & Creative Works

Results of extensive density-functional studies provide direct evidence that Cr atoms in Cr:GaN have a strong tendency to form embedded clusters, occupying Ga sites. Significantly, for larger than 2-Cr-atom clusters, states containing antiferromagnetic coupling with net spin in the range 0.06-1.47 µB/Cr are favored. We propose a picture where various configurations coexist and the statistical distribution and associated magnetism will depend sensitively on the growth details. Such a view may elucidate many puzzling observations related to the structural and magnetic properties of III-N and other dilute semiconductors.

Tunable Conductivity And Conduction Mechanism In An Ultraviolet Light Activated Electronic Conductor, Mariana I. Bertoni, Thomas O. Mason, Julia E. Medvedeva, Arthur J. Freeman, Kenneth R. Poeppelmeier, B. Delley

Physics Faculty Research & Creative Works

A tunable conductivity has been achieved by controllable substitution of an ultraviolet light activated electronic conductor. The transparent conducting oxide system H-doped Ca12-xMgxAl14O33 (x=0,0.1,0.3,0.5,0.8,1.0) presents a conductivity that is strongly dependent on the substitution level and temperature. Four-point dc-conductivity decreases with x from 0.26 S/cm (x=0) to 0.106 S/cm (x=1) at room temperature. At each composition the conductivity increases (reversibly with temperature) until a decomposition temperature is reached; above this value, the conductivity drops dramatically due to hydrogen recombination and loss. The observed conductivity behavior is consistent with the predictions of our first principles density functional calculations for the Mg-substituted …

Crystallization Conditions Of High Silica Rhyolite In The Wichita Mountains, Oklahoma, Ryan Davidson

Opportunities for Undergraduate Research Experience Program (OURE)

Crystal size distribution analysis is being applied to the Carlton Rhyolite of the Wichita Mountains of southwestern Oklahoma. Field observations, descriptions, and sample collection has been completed. Rock samples were cut into slabs and then scanned. From these images the phenocrysts are outlined in CorelDrawl 1 and analyzed using Scion Image to obtain crystal size. Distribution analysis is done using CSD Corrections 1.36 (Higgins 2002). This, in combination with the visible phenocrysts, seems to indicate a flow style of deposition, rather than an airfall.

Measurements Of Combustion - Generated Particulates, Matthew F. Chandler

Opportunities for Undergraduate Research Experience Program (OURE)

Soot particles produced by combustion processes can have a significant impact on such areas as environmental pollution and respiratory hazards. The particulate emissions from high-altitude aircraft engines are especially important. Once the characteristics of the soot aerosols are known, further investigation may determine what methods can be used to control the production of such particulates. Particulate size, concentration, and surface area are factors used to determine its impact on the environment. The differential mobility instruments used for this project are capable of measuring particle sizes from 5 nm to 1000 nm based on the corresponding electrical mobility. The measurements from …

Secondary Reinforcement Requirements For Frp Reinforced Panels, Nathan Branham

Opportunities for Undergraduate Research Experience Program (OURE)

Concrete bridge decks are exposed to some of the harshest weather, that any structural element experience. Regular concrete slabs that rest on earth, are exposed to the same environmental effects, but they also have the ground to help heat them in extreme winter. Bridge decks are surrounded by cold air. This cold environment cause transportation department to cover concrete bridge decks with deicing salts to dissolve ice present on the decks. These deicing salts cause major problems with reinforced concrete. Cracking of concrete bridge decks impose even larger problems, because the cracks allow the chlorides from deicing salts to infiltrate …

Scour On Bridge Piers Due To Flood Waves, Gaston E. Ferrari

Opportunities for Undergraduate Research Experience Program (OURE)

A mathematical solution is presented for approximating the time-dependent scour response to flood waves. This solution is in the form of a convolution integral involving a timevarying scour-forcing function and an exponential scour-response function. In this report, an idealized triangular hydrograph is considered from which an analytic solution is obtained, and also an analytical hydrograph is used from which an analytical solution is also obtained for scour associated with flood waves.

Because of the exponential scour rate, the response obtained from the convolution method is found to lag the scour forcing in time and is damped relative to the maximum …