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Articles 1 - 24 of 24
Full-Text Articles in Engineering
Accuracy And Limitations Of Localized Green’S Function Methods For Materials Science Applications, Duane D. Johnson, Andrei V. Smirnov
Accuracy And Limitations Of Localized Green’S Function Methods For Materials Science Applications, Duane D. Johnson, Andrei V. Smirnov
Duane D. Johnson
We compare screened real-space and reciprocal-space implementations of Korringa-Kohn-Rostoker electronic-structure method for their applicability to largescale problems requiring various levels of accuracy. We show that real-space calculations in metals can become impractical to describe energies. We suggest a combined r- and k-space scheme as the most efficient and flexible strategy for accurate energy calculations. Our hybrid code is suitable for (parallel) large-scale calculations involving complex, multicomponent systems. We also discuss how details of numerical procedures can affect accuracy of such calculations.
Classical Density Functional Theory Of Freezing In Simple Fluids: Numerically Induced False Solutions, M. Valera, F. J. Pinski, Duane D. Johnson
Classical Density Functional Theory Of Freezing In Simple Fluids: Numerically Induced False Solutions, M. Valera, F. J. Pinski, Duane D. Johnson
Duane D. Johnson
Density functional theory (DFT) has provided many insights into the freezing of simple fluids. Several analytical and numerical solution have shown that the DFT provides an accurate description of freezing of hard spheres and their mixtures. Compared to other techniques, numerical, grid-based algorithms for solving the DFT equations have more variational freedom and are capable of describing subtle behavior, as that seen in mixtures with multipeaked density profiles. However the grid-based approach is sensitive to the coarseness of the mesh employed. Here we summarize how the granularity of the mesh affects the freezing point within the DFT. For coarse meshes, …
The Uiuc Virtual Spectrometer: A Java-Based Collaborative Learning Environment, Michael C. Dorneich, Patricia M. Jones
The Uiuc Virtual Spectrometer: A Java-Based Collaborative Learning Environment, Michael C. Dorneich, Patricia M. Jones
Michael C. Dorneich
The development of the UIUC Virtual Spectrometer (UIUC-VS), an interactive, Java-based simulation and tutoring system, is discussed. The apprenticeship model oflearning is utilized to create a learning environment for the study of a one-dimensional proton nuclear magnetic resonance (NMR) experiment, with the goal of linking theoretical knowledge with practical operational experience. Active, exploratory, apprentice-style learning is supported via modes of operation within the system. Students can flexibly choose to "observe the expert" perform and explain operational steps, or "act as an apprentice" and carry out the steps autonomously. Students can switch between modes at their discretion, giving them control of …
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
Stephen D. Holland
We describe a time-resolved method for measuring nonlinear ultrasonic phenomena. Current approaches rely on a narrowband measurement of harmonic generation to identify and characterize nonlinearity. Concomitant with these techniques is poor time resolution. We address this limitation with a hybrid narrowband/broadband approach that provides simultaneous time resolution and harmonic isolation for the measurement of weak nonlinearites. We discuss applications and present demonstrative results showing harmonic generation both in water and at a dry contact aluminum-aluminum interface.
An Analytic Approach Describing Structural Effects On The Properties Of Molecular Fluids, Richard Alan Lesar
An Analytic Approach Describing Structural Effects On The Properties Of Molecular Fluids, Richard Alan Lesar
Richard Alan Lesar
An analytic approach is used to evaluate how the angular structure of a molecular fluid contributes to its thermodynamic properties. The average interactions (energy, forces, etc.) between molecules are first expressed as integrals over a spherical-harmonic expansion of the pair distribution function of the fluid. Angularly averaged interactions for systems described by site−site representations of the intermolecular potentials are then developed. Specifically, homonuclear diatomic molecules described by two-site potential are considered in this paper. These results are used to examine the role that fluid structure plays in determining the average energy, pressure, and forces on a molecule, using as comparison …
Finite-Temperature Dislocation Interactions, Richard Alan Lesar, J. M. Rickman
Finite-Temperature Dislocation Interactions, Richard Alan Lesar, J. M. Rickman
Richard Alan Lesar
We obtain quantitatively the interaction free energy between two fluctuating dislocation lines that are in contact with a thermal bath. By examining both in-plane and transverse-fluctuation polarizations, we identify attractive and repulsive contributions to the free energy and interpret the results in terms of effective multipolar interactions and the screening of separated lines. We find that the usual form of the dislocation force should be modified to include an additional net attractive force when entropic effects are taken into account.
Liquid Dairy Waste Transport And Land Application Cost Comparisons Considering Herd Size, Transport Distance, And Nitrogen Versus Phosphorus Application Rates, Robert T. Burns, A. S. Daugherty, T. L. Cross, D. Raj Raman, G. F. Grandle
Liquid Dairy Waste Transport And Land Application Cost Comparisons Considering Herd Size, Transport Distance, And Nitrogen Versus Phosphorus Application Rates, Robert T. Burns, A. S. Daugherty, T. L. Cross, D. Raj Raman, G. F. Grandle
D. Raj Raman
This study provides cost comparisons for the transport and application of dairy waste slurries based on both phosphorus and nitrogen application rates. Estimated cost comparisons are made for several commonly used systems for dairy waste transport and application. Five dairy sizes ranging from 50 to 2,000 cows using 13 transport and application systems were evaluated. For each dairy size, the costs associated with the transport and application system combinations were determined for transport distances of 0.5, 1.5, and 4.5 miles for both nitrogen and phosphorus-based application rates. Total annual system cost, cost per acre, cost per cow, and manure value …
Incidence Of Escherichia Coli O157:H7, Listeria Monocytogenes , And Salmonella Species On A Tennessee Dairy Farm, T. L. Ervin, R. E. Yoder, F. A. Draughon, Robert T. Burns, D. Raj Raman
Incidence Of Escherichia Coli O157:H7, Listeria Monocytogenes , And Salmonella Species On A Tennessee Dairy Farm, T. L. Ervin, R. E. Yoder, F. A. Draughon, Robert T. Burns, D. Raj Raman
D. Raj Raman
In response to public awareness of foodborne pathogens due to recent outbreaks of illness, a study was conducted on the incidence of Escherichia coli O157:H7, Listeria monocytogenes , and Salmonella species on a dairy farm in middle Tennessee. Sampling locations included water samples from up- and down-stream in a creek running through the farm, free stall bedding, silage, separator liquids, separator solids, pumped liquid from a holding pond, feed, and bulk tank milk. Three samples were taken monthly at each location for 12 months. These samples were tested to determine the incidence of pathogens on the dairy farm and to …
Succeed-Sponsored Freshman Year Engineering Curriculum Improvements At Nc State: A Longitudinal Study Of Retention, Matthew W. Ohland, Sarah A. Rajala, Timothy J. Anderson
Succeed-Sponsored Freshman Year Engineering Curriculum Improvements At Nc State: A Longitudinal Study Of Retention, Matthew W. Ohland, Sarah A. Rajala, Timothy J. Anderson
Sarah A. Rajala
NC State’s involvement in the NSF-sponsored SUCCEED Coalition has led to a number of changes to the freshman year of the engineering curriculum as reported previously (e.g., ASEE 1999, Porter, et al.). An explicit objective of these changes was to retain in engineering those students who were qualified and interested in engineering, but were leaving engineering for other reasons. While a number of isolated innovations have been studied and have demonstrated positive benefit, this study looks at each freshman cohort from 1987 through 1998 to evaluate changes in retention in engineering during that period. Eleven cohorts were studied; five (1987- …
Ec2000 Criterion 2: A Procedure For Creating, Assessing, And Documenting Program Educational Objectives, Michael Carter, Sarah A. Rajala, Rebecca Brent
Ec2000 Criterion 2: A Procedure For Creating, Assessing, And Documenting Program Educational Objectives, Michael Carter, Sarah A. Rajala, Rebecca Brent
Sarah A. Rajala
Criterion 2 [Program Educational Objectives (PEO)] is arguably the most important part of ABET EC2000. PEO embody the broad vision for an engineering program that drives the overall accreditation process. They also provide a crucial nexus point for the assessment of each program, the point at which the programmatic issues of the other EC2000 criteria—curriculum, faculty, facilities, etc.—are considered within the larger context of the needs of key constituencies of the program and the mission of the institution. Criterion 2 plays an essential role in EC2000's goal of encouraging continuous improvement in engineering programs and of providing the opportunity for …
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Statistical Modeling Of Sprays Using The Droplet Distribution Function, Shankar Subramaniam
Shankar Subramaniam
The theoretical foundations of a statistical spray modeling approach based on the droplet distribution function ~ddf!, which was originally proposed by Williams @Phys. Fluids 1, 541 ~1958!#, are established. The equation governing the ddf evolution is derived using an alternative approach. The unclosed terms in the ddf evolution equation are precisely defined, and the regime of applicability of current models is discussed. The theory of point processes is used to rigorously establish the existence of a disintegration of the ddf in terms of a spray intensity, which is the density of expected number of spray droplets in physical space, and …
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Rough Wall Modification Of Two-Layer K-E, Paul A. Durbin, G. Medic, J.-M. Seo, J. K. Eaton, S. Song
Paul A. Durbin
A formulation is developed to apply the two-layer k-ε model to rough surfaces. The approach involves modifying the ℓv formula and the boundary condition on k. A hydrodynamic roughness length is introduced and related to the geometrical roughness through a calibration procedure. An experiment has been conducted to test the model. It provides data on flow over a ramp with and without surface roughness.
Melting And Resolidification Of A Substrate Caused By Molten Microdroplet Impact, Daniel Attinger, D. Poulikakos
Melting And Resolidification Of A Substrate Caused By Molten Microdroplet Impact, Daniel Attinger, D. Poulikakos
Daniel Attinger
This paper describes the main features and results of a numerical investigation of molten microdroplet impact and solidification on a colder flat substrate of the same material that melts due to the energy input from the impacting molten material. The numerical model is based on the axisymmetric Lagrangian Finite-Element formulation of the Navier–Stokes, energy and material transport equations. The model accounts for a host of complex thermofluidic phenomena, exemplified by surface tension effects and heat transfer with solidification in a severely deforming domain. The dependence of the molten volume on time is determined and discussed. The influence of the thermal …
Virtual Classroom For Teaching The Economics Of Engineering Design, Janis P. Terpenny, Kimberly Sward
Virtual Classroom For Teaching The Economics Of Engineering Design, Janis P. Terpenny, Kimberly Sward
Janis P. Terpenny
As decision-makers, engineers must be knowledgeable and competent in multiple aspects of design. Engineering is more than a problem solving activity focusing on simply the expected performance of designed artifacts. Consideration must also be given to the economic consequences of design decisions on life-cycle issues. A major challenge to undergraduate engineering education is to increase student competency in the economic elements that are such a critical part of the engineering process. Many believe that success in this endeavor requires new methods and materials that actively engage students in learning, are more closely aligned with engineering decision-making, and include real-world problems …
Senior Design Projects To Aid The Disabled, Janis P. Terpenny, Robert Gao, John Ritter, Donald Fisher, Sundar Krishnamurty
Senior Design Projects To Aid The Disabled, Janis P. Terpenny, Robert Gao, John Ritter, Donald Fisher, Sundar Krishnamurty
Janis P. Terpenny
A new two-semester capstone senior design course sequence in the area of assistive technology has been developed and integrated within the established curriculum of the Department of Mechanical and Industrial Engineering (MIE) at the University of Massachusetts (UMass) Amherst. Entitled “Senior Design Projects to Aid the Disabled,” the capstone sequence includes close collaborations with the Lemelson Assistive Technology Development Center (LATDC) at Hampshire College and Adaptive Design Services (ADS) under the Massachusetts Department of Mental Retardation (DMR). The new design course allows students to work directly with collaborators and disabled clients to solve specific assistive technology design problems. Through these …
Unbiased Density Functional Solutions Of Freezing In Binary Mixtures Of Hard Or Soft Spheres, M. Valera, R. F. Bielby, F. J. Pinksi, Duane D. Johnson
Unbiased Density Functional Solutions Of Freezing In Binary Mixtures Of Hard Or Soft Spheres, M. Valera, R. F. Bielby, F. J. Pinksi, Duane D. Johnson
Duane D. Johnson
various size ratios, σ2/σ1, using density functional theory. The Grand Potential is minimized using an unbiased, discrete, real-space mesh that does not constrain the shape of the density, and, in many cases, leads to solutions qualitatively different from those using Gaussians and plane-waves. Besides the usual face-centered-cubic solid-solution phase for σ2/σ1≈1.0, we find a sublattice-melt phase for σ2/σ1=0.85–0.5 (where the small-sphere density is nonlocalized and multi-peaked) and the NaCl phase for σ2/σ1=0.45–0.35 (when the small-sphere density again sharpens). For a range of size ratios of soft sphere mixtures, we could not find stable nonuniform solutions. Preliminary calculations within a Modified-Weighted …
Static Friction And Surface Roughness Studies Of Surface Micromachined Electrostatic Micromotors Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan
Static Friction And Surface Roughness Studies Of Surface Micromachined Electrostatic Micromotors Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan
Sriram Sundararajan
A technique to measure the static friction forces (stiction) encountered in surface micromachined micromotors using a commercial atomic force microscope (AFM)/friction force microscope has been developed and is described. An AFM tip is pushed against a rotor arm of the micromotor so as to generate lateral deflection (torsion) of the tip, which is measured by the AFM. The maximum value of the lateral deflection obtained prior to rotor movement (rotation) is a measure of the static friction force of the micromotors. This technique was employed to study the effect of humidity and rest time on the static friction force of …
Development Of A Continuous Microscratch Technique In An Atomic Force Microscope And Its Application To Study Scratch Resistance Of Ultrathin Hard Amorphous Carbon Coatings, Sriram Sundararajan, Bharat Bhushan
Development Of A Continuous Microscratch Technique In An Atomic Force Microscope And Its Application To Study Scratch Resistance Of Ultrathin Hard Amorphous Carbon Coatings, Sriram Sundararajan, Bharat Bhushan
Sriram Sundararajan
A method to measure friction during scratching at linearly increasing loads in a commercial atomic force/friction force microscope (AFM/FFM) has been developed. The normal load was increased in small increments over the required range for the scratch using a software module while the friction signal was measured via a breakout box and data acquisition computer. Topography images of the scratch were obtained in situ with the AFM in tapping mode with minimal loss of damage event information. This technique was employed to study the scratch resistance of hard amorphous carbon coatings of thicknesses ranging from 20 nm down to 3.5 …
Cramér-Rao Bounds For Estimating Range, Velocity, And Direction With An Active Array, Aleksandar Dogandžić, Arye Nehorai
Cramér-Rao Bounds For Estimating Range, Velocity, And Direction With An Active Array, Aleksandar Dogandžić, Arye Nehorai
Aleksandar Dogandžić
We derive Cramer-Rao bound (CRB) expressions for the range (time delay), velocity (Doppler shift), and direction of a point target using an active radar or sonar array. First, general CRB expressions are derived for a narrowband signal and array model and a space-time separable noise model that allows both spatial and temporal correlation. We discuss the relationship between the CRB and ambiguity function for this model. Then, we specialize our CRB results to the case of temporally white noise and the practically important signal shape of a linear frequency modulated (chirp) pulse sequence. We compute the CRB for a three-dimensional …
Determination Of 17ss-Estradiol Concentrations In Runoff From Plots Receiving Dairy Manure, A. R. Dyer, D. Raj Raman, M. D. Mullen, Robert T. Burns, Lara B. Moody, A. C. Layton
Determination Of 17ss-Estradiol Concentrations In Runoff From Plots Receiving Dairy Manure, A. R. Dyer, D. Raj Raman, M. D. Mullen, Robert T. Burns, Lara B. Moody, A. C. Layton
D. Raj Raman
Because of growing concern about estrogenic compounds in animal wastes, the objective of this research was to measure 17 ß -estradiol concentrations in runoff from plots fertilized with liquid dairy waste. Nine plots were established at The University of Tennessee Dairy Experiment Station located at Lewisburg, Tennessee, and dairy manure was applied to six of the nine plots. Three of the plots received manure at a rate sufficient to meet the nitrogen (N) requirement for winter wheat; three received manure at a rate sufficient to meet the phosphorus (P) requirement for winter wheat, and three received no manure. Runoff samples …
Enhancing Dairy Lagoon Performance With High-Rate Anaerobic Digesters, Gary L. Hawkins, D. Raj Raman, Robert T. Burns, Ronald E. Yoder, Tim L. Cross
Enhancing Dairy Lagoon Performance With High-Rate Anaerobic Digesters, Gary L. Hawkins, D. Raj Raman, Robert T. Burns, Ronald E. Yoder, Tim L. Cross
D. Raj Raman
In a two–stage study, the possibility of using high–rate anaerobic digesters to enhance the performance of dairy lagoons was explored. Four anaerobic sequencing batch reactors (ASBR) and four downflow anaerobic filters (DFAF) were tested, with two of each type operated at 25C, and the other two at 35C. The first stage of the experiment explored using the high–rate digesters on liquid effluent from a screw–press treating dairy manure slurry. The first–stage experiment demonstrated that settling processes, rather than biodegradation, accounted for most of the organic matter reduction in both reactor types, when operated at a 0.5–d hydraulic retention time. Specifically, …
Degradation Of Estrogens In Dairy Waste Solids: Effects Of Acidification And Temperature, D. Raj Raman, Alice C. Layton, Lara B. Moody, James P. Easter, Gary S. Sayler, Robert T. Burns
Degradation Of Estrogens In Dairy Waste Solids: Effects Of Acidification And Temperature, D. Raj Raman, Alice C. Layton, Lara B. Moody, James P. Easter, Gary S. Sayler, Robert T. Burns
D. Raj Raman
Manure–borne estrogens are increasingly recognized as a potential ecological hazard. However, sample–handling protocols for these compounds are not clearly delineated in the literature, nor are comparisons between assays for estrogens. A study was conducted to explore the degradation of estrogen in separated dairy manure waste solids (press cake), using three popular assay types. Estrogens were measured by enzyme–linked immunosorbent assay (ELISA), gas–chromatography mass–spectroscopy (GC–MS) and a recombinant yeast estrogen reporter assay. As measured by GC–MS, background estrone concentrations were approximately 100 ppb, while 17β–estradiol concentrations were one–third of the estrone concentration, and 17β–estradiol concentrations were below the detection limit (10 …
Evaluation Of Fabric Swatch Types For Relative Odor Intensity At Beef Cattle Feedyards, Sean D. See, David B. Parker, Brent W. Auvermann, Jacek A. Koziel, John Sweeten
Evaluation Of Fabric Swatch Types For Relative Odor Intensity At Beef Cattle Feedyards, Sean D. See, David B. Parker, Brent W. Auvermann, Jacek A. Koziel, John Sweeten
Jacek A. Koziel
A research project was conducted to determine which type of fabric swatch was best suited for on-site sampling of odor intensity at open-lot beef cattle feeding operations. Five different types of fabric were tested: cotton flannel, cotton muslin, acetate, polyester and polyester felt. Square swatches (20 × 20 cm) were suspended 1 m above the ground surface downwind of cattle pens for 24 hours. The swatches were placed in glass jars and presented to 8-10 human panelists who were asked to rank the swatches based on relative odor intensity. Five trials were conducted at 3 feedyards. Sums of ranks and …
Air Sampling With Solid Phase Microextraction, Jacek A. Koziel, Fabio Augusto, Janusz Pawliszyn
Air Sampling With Solid Phase Microextraction, Jacek A. Koziel, Fabio Augusto, Janusz Pawliszyn
Jacek A. Koziel
Solid phase microextraction (SPME) presents many advantages over conventional analytical methods by combining sampling, pre-concentration and direct transfer of the VOCs into a standard gas chromatography (GC) system. Since its introduction SPME has been applied to the sampling and analysis of environmental samples including airborne VOCs and particulates. The first part of this paper presents theory of air sampling with SPME and an overview of the a few current methods for quantitative air sampling and VOC determination with SPME using grab (‘instantaneous”) and time-weighted average (TWA) modes. The second part of this paper is focused on the recent development of …