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Articles 1 - 18 of 18
Full-Text Articles in Engineering
Temperature-Induced Configurational Excitations For Predicting Thermodynamic And Mechanical Properties Of Alloys, Duane D. Johnson, Andrei V. Smirnov, J. B. Staunton, F. J. Pinski, W. A. Shelton
Temperature-Induced Configurational Excitations For Predicting Thermodynamic And Mechanical Properties Of Alloys, Duane D. Johnson, Andrei V. Smirnov, J. B. Staunton, F. J. Pinski, W. A. Shelton
Duane D. Johnson
We show that a structural energy difference, ΔE, must include explicit symmetry-breaking changes of the electronic structure due to temperature-induced configurational excitations, and why ΔE at T=0 K is not necessarily relevant to thermodynamic and mechanical modeling. In Ni3V, we calculate a tenfold decrease of ΔE between D022 and L12 structures from T=0 K to states of order relevant to experiment. ΔE calculated directly from states with short-range order (8 meV) or with low partial order (7–12 meV) agree with high-T experiment (10 meV).
Statistical Representation Of A Spray As A Point Process, Shankar Subramaniam
Statistical Representation Of A Spray As A Point Process, Shankar Subramaniam
Shankar Subramaniam
The statistical representation of a spray as a finite point process is investigated. One objective is to develop a better understanding of how single-point statistical information contained in descriptions such as the droplet distribution function ~ddf!, relates to the probability density functions ~pdfs! associated with the droplets themselves. Single-point statistical information contained in the droplet distribution function ~ddf! is shown to be related to a sequence of single surrogate-droplet pdfs, which are in general different from the physical single-droplet pdfs. It is shown that the ddf contains less information than the fundamental single-point statistical representation of the spray, which is …
Damper For Brake Noise Reduction (Brake Drums), Jonathan A. Wickert, Adnan Akay
Damper For Brake Noise Reduction (Brake Drums), Jonathan A. Wickert, Adnan Akay
Jonathan A. Wickert
An apparatus of reducing unwanted brake noise has a ring damper affixed around a periphery of brake drum in a drum brake system in a manner that permits relative motion and slippage between the ring damper and the brake drum when the brake drum vibrates during braking. In a preferred embodiment, the ring damper is an almost circular ring that is inserted in a groove formed in the periphery of the brake drum. The ring damper is held in place by the groove itself and by the interference pre-load or pre-tension between the ring damper and the brake drum.
Avhrr Estimates Of Surface Temperature During The Southern Great Plains 1997 Experiment, Amy L. Kaleita, Praveen Kumar
Avhrr Estimates Of Surface Temperature During The Southern Great Plains 1997 Experiment, Amy L. Kaleita, Praveen Kumar
Amy L. Kaleita
In this study we aim to (1) explore the differences in the accuracy of satellitederived land-surface skin temperature for day and nighttime observations, (2) assess the effects of large solar zenith angles, and (3) develop an understanding of the spatial variability of the observed temperatures. Land-surface skin temperatures are obtained using the split-window technique from observations of the AVHRR instrument aboard the NOAA-12 and NOAA-14 satellites for the SGP97 (Southern Great Plains 1997) hydrology experiment. From the study of several days of observations we find that observed biases with respect to the ground temperature, both during day and night, are …
North Carolina State University Summer Transition Program – A High School To College Bridge Program For Enhancing Undergraduate Engineering Education, Tony L. Mitchell, Alisa Hunt-Lowery, Sarah A. Rajala
North Carolina State University Summer Transition Program – A High School To College Bridge Program For Enhancing Undergraduate Engineering Education, Tony L. Mitchell, Alisa Hunt-Lowery, Sarah A. Rajala
Sarah A. Rajala
The NC State University College of Engineering is an internationally recognized producer of engineers and computer scientists who are prepared to make an immediate contribution to the workforce. Our research faculty are recognized around the world for cutting edge research. Essential to our mission and continued success is a steady stream of top-notch students who contribute to and celebrate ethnic, academic and gender diversity. Each year an entering freshman class of 1100 new engineering students includes 20% women and 20% underrepresented minority students. The rate at which they persist through our undergraduate program is impacted by how they adapt during …
North Carolina State University Center For Minority Engineer Development, Tony L. Mitchell, Sarah A. Rajala, Laura J. Bottomley, Mary Clare Robbins
North Carolina State University Center For Minority Engineer Development, Tony L. Mitchell, Sarah A. Rajala, Laura J. Bottomley, Mary Clare Robbins
Sarah A. Rajala
North Carolina State University, located in Raleigh, North Carolina, USA, is the largest state-supported university of the sixteen-campus University of North Carolina educational system. The College of Engineering at NC State University is among the best in the country, offering outstanding degree programs and preparing students for exciting and rewarding careers. Our graduates are heavily recruited internationally for positions in a variety of settings, including business management, construction, transportation, hardware and software development, computer engineering and design. The College of Engineering comprises 10 departments offering 16 BS, 17 MS, and 14 Ph.D. degree programs and conducts the largest undergraduate and …
Developing Construction Claims For Arbitration: Two Arbitrators' Viewpoint, Douglas D. Gransberg, Charles A. Joplin
Developing Construction Claims For Arbitration: Two Arbitrators' Viewpoint, Douglas D. Gransberg, Charles A. Joplin
Douglas D. Gransberg
Two arbitrators' viewpoints of construction claims development are provided in the hope that the information will be useful to those needing to resolve construction claims by arbitration. It also may help to reduce the volume of costly and unnecessary documentation. Because of arbitration's relative formality, attorneys representing construction contractors and owners tend to prepare their cases in the same way as they would for litigation. This leads to potential information overkill, which threatens the arbitration panel's ability to easily sort through and understand the issues in its quest for a fair and equitable decision.
Spin Fluctuations In Nearly Magnetic Metals From Ab Initio Dynamical Spin Susceptibility Calculations: Application To Pd And Cr95v5, J. B. Staunton, J. Poulter, B. Ginatempo, E. Bruno, Duane D. Johnson
Spin Fluctuations In Nearly Magnetic Metals From Ab Initio Dynamical Spin Susceptibility Calculations: Application To Pd And Cr95v5, J. B. Staunton, J. Poulter, B. Ginatempo, E. Bruno, Duane D. Johnson
Duane D. Johnson
We describe our theoretical formalism and computational scheme for making ab initio calculations of the dynamic paramagnetic spin susceptibilities of metals and alloys at finite temperatures. Its basis is time-dependent density functional theory within an electronic multiple scattering, imaginary time Green function formalism. Results receive a natural interpretation in terms of overdamped oscillator systems making them suitable for incorporation into spin fluctuation theories. For illustration we apply our method to the nearly ferromagnetic metal Pd and the nearly antiferromagnetic chromium alloy Cr95V5. We compare and contrast the spin dynamics of these two metals and in each case identify those fluctuations …
Scaling And Parameterization Of Stratified Homogeneous Turbulent Shear Flow, Lucinda H. Shih, Jeffrey R. Koseff, Joel H. Ferziger, Chris R. Rehmann
Scaling And Parameterization Of Stratified Homogeneous Turbulent Shear Flow, Lucinda H. Shih, Jeffrey R. Koseff, Joel H. Ferziger, Chris R. Rehmann
Chris R. Rehmann
Homogeneous sheared stratified turbulence was simulated using a DNS code. The initial turbulent Reynolds numbers (Re) were 22, 44, and 89, and the initial dimensionless shear rate (S*) varied from 2 to 16. We found (similarly to Rogers (1986) for unstratified flows) the final value of S* at high Re to be [similar] 11, independent of initial S*. The final S* varies at low Re, in agreement with Jacobitz et al. (1997). At low Re, the stationary Richardson number (Ris) depends on both Re and S*, but at higher Re, it varies only with Re. A scaling based on the …
Diapycnal Diffusivity Inferred From Scalar Microstructure Measurements Near The New England Shelf/Slope Front, Chris R. Rehmann, Timothy F. Duda
Diapycnal Diffusivity Inferred From Scalar Microstructure Measurements Near The New England Shelf/Slope Front, Chris R. Rehmann, Timothy F. Duda
Chris R. Rehmann
Conductivity microstructure was used to estimate the diapycnal thermal eddy diffusivity KT near the New England shelf/slope front in early August 1997. Two datasets were collected with a towed vehicle. One involved several horizontal tows in and above a warm, salty layer near the seafloor, and the other was from a tow-yo transect that sampled most of the water column. In the bottom layer, KT derived from microstructure is a factor of about 5 smaller than estimates derived from tracer dispersion at the same density level, and the diffusivity decreases sharply as the buoyancy frequency N increases: KT N−3.1. With …
An Experimental Study Of Molten Microdroplet Surface Deposition And Solidification: Transient Behavior And Wetting Angle Dynamics, Daniel Attinger, Z. Zhao, D. Poulikakos
An Experimental Study Of Molten Microdroplet Surface Deposition And Solidification: Transient Behavior And Wetting Angle Dynamics, Daniel Attinger, Z. Zhao, D. Poulikakos
Daniel Attinger
The basic problem of the impact and solidification of molten droplets on a substrate is of central importance to a host of processes. An important and novel such process in the area of micromanufacturing is solder jetting where microscopic solder droplets are dispensed for the attachment of microelectronic components. Despite the recent appearance of a few numerical studies focusing on the complex transient aspects of this process, no analogous experimental results have been reported to date to the best of our knowledge. Such a study is reported in this paper. Eutectic solder (63Sn37Pb) was melted to a preset superheat and …
Topography-Induced Contributions To Friction Forces Measured Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan
Topography-Induced Contributions To Friction Forces Measured Using An Atomic Force/Friction Force Microscope, Sriram Sundararajan, Bharat Bhushan
Sriram Sundararajan
Most friction studies using an atomic force/friction force microscope, while concentrating on material-induced effects, often present users with conflicting and confusing interpretations of the topography-induced friction forces. It has been generally reported that topography-induced contributions are independent of scanning direction and can be removed by subtracting friction data from forward and backward scans. In this article, we present friction studies on samples with well-defined topography variations and find that the above-given statement is not generally true. At surface locations involving significant changes in topography, the topography-induced contributions to friction forces are found to be different between forward and backward scanning …
Spatial Modulation Of Repeated Vibration Modes In Rotationally Periodic Structures, M. Kim, J. Moon, Jonathan A. Wickert
Spatial Modulation Of Repeated Vibration Modes In Rotationally Periodic Structures, M. Kim, J. Moon, Jonathan A. Wickert
Jonathan A. Wickert
When a structure deviates from axisymmetry because of circumferentially varying model features, significant changes can occur to its natural frequencies and modes, particularly for the doublet modes that have non-zero nodal diameters and repeated natural frequencies in the limit of axisymmetry. Of technical interest are configurations in which inertia, dissipation, stiffness, or domain features are evenly distributed around the structure. Aside from the well-studied phenomenon of eigenvalue splitting, whereby the natural frequencies of certain doublets split into distinct values, modes of the axisymmetric structure that are precisely harmonic become contaminated with certain additional wavenumbers. From analytical, numerical, and experimental perspectives, …
Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King
Behavior Of Grain Boundary Resistivity In Metals Predicted By A Two-Dimensional Model, Rand Dannenberg, Alexander H. King
Alexander H. King
The behavior of a model for the specific grain boundary resistivity in metallic bamboo conductor lines is developed and compared to other theoretical treatments, and to experiment. The grain boundary is modeled as an array of scatterers on a plane. The scatterers are called “vacancy-ion” complexes, in which the vacancy represents the boundary free volume, and the ion is an atom adjacent to the vacancy. Three cases are investigated, that of noninterfering scatterers, a continuum of interfering scatterers, and discrete interfering scatterers. The approximations used lead to a specific grain boundary resistivity ∼10−16 Ω m2 for aluminum, in agreement with …
Direct Observations Of Electric Field-Induced Domain Boundary Cracking In 〈001〉 Oriented Piezoelectric Pb(Mg1/3nb2/3)O3–Pbtio3 Single, Xiaoli Tan, Z. Xu, J.K. Shang, P. Han
Direct Observations Of Electric Field-Induced Domain Boundary Cracking In 〈001〉 Oriented Piezoelectric Pb(Mg1/3nb2/3)O3–Pbtio3 Single, Xiaoli Tan, Z. Xu, J.K. Shang, P. Han
Xiaoli Tan
In situtransmission electron microscopy study of electric field-induced cracking has been conducted on 〈001〉 oriented 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 crystal. Fracture of the 90° domain boundary was directly observed in the tetragonal area under both static and alternating electric fields. The field strength required to induce domain boundary cracking was lower for alternating electric field than for static field.
Experimental And Theoretical Modeling Of Dynamically Loaded Surface Foundations On Granular Soils, Jeramy C. Ashlock
Experimental And Theoretical Modeling Of Dynamically Loaded Surface Foundations On Granular Soils, Jeramy C. Ashlock
Jeramy C. Ashlock
The mechanical properties of a cohesionless granular medium are strongly dependent on the confining stress, which varies three-dimensionally under a surface foundation due to gravitational and surface loading effects. Success in predicting a foundation’s response to dynamic loading is therefore highly dependent on the appropriate choice of material properties for a given theoretical model. Presented in this thesis are critical results from an investigation of dynamically loaded square foundations on granular soil using a geotechnical centrifuge. From the results, it is shown that the characterization of the vertical mode of vibration of the square foundations via the homogeneous half-space theory …
In Situ Transmission Electron Microscopy Study Of Electric-Field-Induced Microcracking In Single Crystal Pb(Mg1/3nb2/3)O3–Pbtio3, Z. Xu, Xiaoli Tan, P. Han, J.K. Shang
In Situ Transmission Electron Microscopy Study Of Electric-Field-Induced Microcracking In Single Crystal Pb(Mg1/3nb2/3)O3–Pbtio3, Z. Xu, Xiaoli Tan, P. Han, J.K. Shang
Xiaoli Tan
In this letter, we report in situ transmission electron microscopy (TEM) study of effect of a cyclic electric field on microcracking in a single crystal piezoelectric 0.66Pb(Mg1/3Nb2/3)O3–0.34PbTiO3. A TEM heating stage was modified to permit the in situ application of an electric field on the TEM sample surface. Microcrack initiation from a fine pore under an applied cyclic electric field was directly observed in the piezoelectric single crystal. Experimental procedures for in situ TEM studies were described.
Estimating Evoked Dipole Responses In Unknown Spatially Correlated Noise With Eeg/Meg Arrays, Aleksandar Dogandžić, Arye Nehorai
Estimating Evoked Dipole Responses In Unknown Spatially Correlated Noise With Eeg/Meg Arrays, Aleksandar Dogandžić, Arye Nehorai
Aleksandar Dogandžić
We present maximum likelihood (ML) methods for estimating evoked dipole responses using electroencephalography (EEG) and magnetoencephalography (MEG) arrays, which allow for spatially correlated noise between sensors with unknown covariance. The electric source is modeled as a collection of current dipoles at fixed locations and the head as a spherical conductor. We permit the dipoles' moments to vary with time by modeling them as linear combinations of parametric or nonparametric basis functions. We estimate the dipoles' locations and moments and derive the Cramer-Rao bound for the unknown parameters. We also propose an ML based method for scanning the brain response data, …