Engineering Commons^™

Low Temperature Epitaxial Growth Of Ge Quantum Dot On Si (100) - (2×1) By Femtosecond Laser Excitation, Ali Oguz Er, Wei Ren, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Low temperature epitaxy of Ge quantum dots on Si (100) - (2×1) by femtosecond pulsed laser deposition under femtosecond laser excitation was investigated. Reflection high-energy electron diffraction and atomic force microscopy were used to analyze the growth mode and morphology. Epitaxial growth was achieved at ∼70 °C by using femtosecond laser excitation of the substrate. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed. © 2011 American Institute of Physics. [doi:10.1063/1.3537813]

Do We Need M&S Science?, Jose J. Padilla, Saikou Y. Diallo, Andreas Tolk

VMASC Publications

No abstract provided.

Coherent Phonons In Bismuth Film Observed By Ultrafast Electron Diffraction, A. Bugayev, A. Esmail, M. Abdel-Fattah, H. E. Elsayed-Ali

Applied Research Center Publications

The generation of coherent phonons in polycrystalline bismuth film excited with femtosecond laser pulse is observed by ultrafast time-resolved electron diffraction. The dynamics of the diffracted intensities from the (110), (202), and (024) lattice planes show pronounced oscillations at 130-150 GHz. The origin of these coherent acoustic phonons is discussed in view of optical phonon decay into two acoustic phonons. Different drop times in the intensity of the diffraction orders are observed and interpreted as anisotropy in the energy transfer rate of coherent optical phonons.

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, steady-state viscous axial vortex with specified far-field circulation. When sound generation is attributed to a velocity gradient tensor-pressure 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 circulation-based Reynolds numbers. The influence of temperature and humidity on the pressure relaxation coefficient in air has been examined using theoretical and empirical approaches, and …

Simulation And Visualization Enhanced Engineering Education- Development And Implementation Of Virtual Experiments In A Laboratory Course, Sushil K. Chaturvedi, Kaustubh A. Dharwadkar

Mechanical & Aerospace Engineering Faculty Publications

This paper presents results from a National Science Foundation grant titled "Simulation and Visualization Enhanced Engineering Education", funded by the EEC division. Although the scope of the project is quite broad, embracing a wide range of courses in three engineering disciplines, the present work describes the results obtained from application of simulation and visualization for development and implementation of web-based virtual engineering laboratories. The present work leverages the advancement in hardware and software technologies to map physical experiments into web-based virtual experiments that can be used to enrich student's laboratory experience. Four physical experiments in the thermo-fluids laboratory course have …

Fourier Transform Emission Spectroscopy Of Yh And Yd: Observation Of New A¹Δ And B¹Π Electronic States, R. S. Ram, G. Li, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

The emission spectra of YH and YD molecules have been investigated in the 3600–12 000 cm⁻¹ region using a Fourier transform spectrometer. Molecules were formed in an yttrium hollow cathode lamp operated with a continuous flow of a mixture of Ne and Ar gases, and YH and YD were observed together in the same spectra. A group of bands observed near 1 μm have been identified as 0-0 and 1-1 bands of the A¹Δ-X¹Σ⁺ and B¹Π-X¹Σ⁺ transitions of YH and the 0-0 bands of the same two transitions …

Spatio-Temporal Variations In Soil Moisture And Physicochemical Properties Of A Typical Semiarid Sand-Meadow-Desert Landscape As Influenced By Land Use, L. Duan, T. Liu, X. Wang, G. Wang, L. Ma, Y. Luo

Civil & Environmental Engineering Faculty Publications

A good understanding of the interrelations between land cover alteration and changes in hydrologic conditions (e.g., soil moisture) as well as soil physicochemical properties (e.g., fine soil particles and nutrients) is crucial for maintaining the fragile hydrologic and environmental conditions of semiarid land, such as the Horqin Sandy Land in China, but is lacking in existing literature. The objectives of this study were to examine: (1) spatio-temporal variations of soil moisture and physicochemical properties in semiarid land; and (2) how those variations are influenced by land cover alteration. Using the data collected in a 9.71 km2 well-instrumented area of the …

Nonuniformity In Lattice Contraction Of Bismuth Nanoclusters Heated Near Its Melting Point, A. Esmail, M. Abdel-Fattah, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 ± 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of ∼14 nm along the minor axis and ∼16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 ± 6 K along the [012] direction and 86 ± 9 K along the [110] …

Towards Reducing Traffic Congestion Using Cooperative Adaptive Cruise Control On A Freeway With A Ramp, George Arnaout, Shannon Bowling

Engineering Management & Systems Engineering Faculty Publications

Purpose: In this paper, the impact of Cooperative Adaptive Cruise Control (CACC) systems on traffic performance is examined using microscopic agent-based simulation. Using a developed traffic simulation model of a freeway with an on-ramp - created to induce perturbations and to trigger stop-and-go traffic, the CACC system’s effect on the traffic performance is studied. The previously proposed traffic simulation model is extended and validated. By embedding CACC vehicles in different penetration levels, the results show significance and indicate the potential of CACC systems to improve traffic characteristics and therefore can be used to reduce traffic congestion. The study shows that …

Selection Of Source And Use Of Traffic Information In Emergency Situations, R. Michael Robinson, Asad Khattak

VMASC Publications

The access and the use of advanced traveler information systems (ATISs) by drivers during normal commuting have been extensively assessed and analyzed. Emergency managers and transportation officials have extended the results of studies of ATIS use under routine conditions to emergency scenarios under the assumption that drivers' responses to information under emergency conditions mimic those seen under normal driving conditions. A recent survey of potential hurricane evacuees suggests the need to revisit this assumption. Results indicate that although commercial radio reports and variable message signs continue to be the sources of traffic information cited the most frequently, other information sources …

Poincare Recurrence And Spectral Cascades In Three-Dimensional Quantum Turbulence, George Vahala, Jeffrey Yepez, Linda L. Vahala, Min Soe, Bo Zhang, Sean Ziegeler

Electrical & Computer Engineering Faculty Publications

The time evolution of the ground state wave function of a zero-temperature Bose-Einstein condensate (BEC) gas is well described by the Hamiltonian Gross-Pitaevskii (GP) equation. Using a set of appropriately interleaved unitary collision-stream operators, a qubit lattice gas algorithm is devised, which on taking moments, recovers the Gross-Pitaevskii (GP) equation under diffusion ordering (time scales as length²). Unexpectedly, there is a class of initial states whose Poincaré recurrence time is extremely short and which, as the grid resolution is increased, scales with diffusion ordering (and not as length³). The spectral results of J. Yepez et al. …

Imbalanced Learning For Functional State Assessment, Feng Li, Frederick Mckenzie, Jiang Li, Guanfan Zhang, Roger Xu, Carl Richey, Tom Schnell, Thomas E. Pinelli (Ed.)

Electrical & Computer Engineering Faculty Publications

This paper presents results of several imbalanced learning techniques applied to operator functional state assessment where the data is highly imbalanced, i.e., some function states (majority classes) have much more training samples than other states (minority classes). Conventional machine learning techniques usually tend to classify all data samples into majority classis and perform poorly for minority classes. In this study, we implemented five imbalanced learning techniques, including random under-sampling, random over-sampling, synthetic minority over-sampling technique (SMOTE), borderline-SMOTE and adaptive synthetic sampling (ADASYN) to solve this problem. Experimental results on a benchmark driving test dataset show that accuracies for minority classes …

Enhancement Technique For Aerial Images, Sertan Erkanli, Ahmet Gungor Pakfiliz, Jiang Li

Electrical & Computer Engineering Faculty Publications

Recently, we proposed an enhancement technique for uniformly and non-uniformly illuminated dark images that provides high color accuracy and better balance between the luminance and the contrast in images to improve the visual representations of digital images. In this paper we define an improved version of the proposed algorithm to enhance aerial images in order to reduce the gap between direct observation of a scene and its recorded image.

Electronically Enhanced Surface Diffusion During Ge Growth On Si(100), Ali Orguz Er, Hani E. Elsayed-Ali

Physics Faculty Publications

The effect of nanosecond pulsed laser excitation on surface diffusion during the growth of Ge on Si(100) at 250 °C was studied. In situ reflection high-energy electron diffraction was used to measure the surface diffusion coefficient while ex situ atomic force microscopy was used to probe the structure and morphology of the grown quantum dots. The results show that laser excitation of the substrate increases the surface diffusion during the growth of Ge on Si(100), changes the growth morphology, improves the crystalline structure of the grown quantum dots, and decreases their size distribution. A purely electronic mechanism of enhanced surface …

Structural Characterization Of Nb Films Deposited By Ecr Plasma Energetic Deposition On Crystalline Insulators, Xin Zhao, A. -M. Valente-Feliciano, J. K. Spradlin, H. L. Phillips, C. E. Reece, D. Gu, H. Baumgart, K. Seo

Physics Faculty Publications

An energetic condensation thin film coating technique with an electron cyclotron resonance (ECR) induced Niobium (Nb) plasma ion source is used to deposit Nb thin films on crystalline insulating substrates, such as a-plane and c-plane sapphire (Al₂O₃) and on magnesium oxide, MgO (100), (110), and (111).

Hetero-epitaxial Nb films were produced by ECR deposition with regulated substrate temperature. The residual resistivity ratio (RRR) of about 1 micron thick films on a-plane (1,1,-2,0) sapphire substrates reach values (350 - 450) comparable to high RRR bulk NB commonly used for SRF cavities.

The epitaxial relationship of Nb/crystalline substrate is found to be …

Balloon Borne Mars Research Platforms, Sean Michael Hancock

Mechanical & Aerospace Engineering Theses & Dissertations

Aerial platforms can fill a measurement gap between orbiters and rovers, providing planetary scale high resolution in situ measurements, access to scientifically interesting terrain that is either inaccessible or hazardous to rovers, and serve as a planet-wide delivery platforms to deploy surface probes and rovers to areas inaccessible given existing entry, descent, and landing systems. A permanent robotic outpost on the Martian surface can utilize locally-derived hydrogen as a lifting gas for balloon systems deployed from Mars. That approach can simplify the inflation and launch of aerial vehicles while allowing for a long duration deployment campaign that is not constrained …

An Integrated Computer-Aided Robotic System For Dental Implantation, Xiaoyan Sun, Yongki Yoon, Jiang Li, Frederic D. Mckenzie

Electrical & Computer Engineering Faculty Publications

This paper describes an integrated system for dental implantation including both preoperative planning utilizing computer-aided technology and automatic robot operation during the intra-operative stage. A novel two-step registration procedure was applied for transforming the preoperative plan to the operation of the robot, with the help of a Coordinate Measurement Machine (CMM). Experiments with a patient-specific phantom were carried out to evaluate the registration error for both position and orientation. After adopting several improvements, registration accuracy of the system was significantly improved. Sub-millimeter accuracy with the Target Registration Errors (TREs) of 0.38±0.16 mm (N=5) was achieved. The target orientation errors after …

Impact Of Project Based Learning In Introduction To Engineering/Technology Class, Alok K. Verma

Engineering Technology Faculty Publications

Project based learning (PBL) has a proven record as a teaching tool. Concepts that are often hard to grasp are made easy by the use of project based activities. The constructivism learning theory suggests that people learn better by actively participating in the process of learning. The Introduction to Engineering and Engineering Technology class has been modified to include project based learning kits to engage freshmen early on in the program. The goal is to demonstrate students the link between the scientific principles and their engineering applications. The course is team taught by faculty from various engineering and technology disciplines …

Design And Implement A Cost-Effective Wireless Communication Project On A Pic Training System, Steve Hsiung, Walter F. Deal, Lacides Agustin Osorio, Mathew Henderson

Engineering Technology Faculty Publications

Wireless communication becomes popular and widely used in almost every electronic product in our daily life. The RF communication is one of the major wireless applications in consumer products. Usually, it is integrated with an embedded system (microcontroller) to control various applications such as temperature sensing, data logging, data exchange, actuator activation, and user interaction wirelessly. A project based model can be used as an effective instructional strategy to enhance learning about complex RF concepts and technologies. The project method can lead to improved understanding and create interest by actively engaging the student with hands-on and problem solving and critical …

Bcc Skin Cancer Diagnosis Based On Texture Analysis Techniques, Shao-Hui Chuang, Xiaoyan Sun, Wen-Yu Chang, Gwo-Shing Chen, Adam Huang, Jiang Li, Frederic D. Mckenzie

Electrical & Computer Engineering Faculty Publications

In this paper, we present a texture analysis based method for diagnosing the Basal Cell Carcinoma (BCC) skin cancer using optical images taken from the suspicious skin regions. We first extracted the Run Length Matrix and Haralick texture features from the images and used a feature selection algorithm to identify the most effective feature set for the diagnosis. We then utilized a Multi-Layer Perceptron (MLP) classifier to classify the images to BCC or normal cases. Experiments showed that detecting BCC cancer based on optical images is feasible. The best sensitivity and specificity we achieved on our data set were 94% …

On The Visual Quality Enhancement Of Super-Resolution Images, Amr Hussein Yousef, Jiang Li, Mohammad Karim, Andrew G. Tescher (Ed.)

Electrical & Computer Engineering Faculty Publications

Super-resolution (SR) is the process of obtaining a higher resolution image from a set of lower resolution (LR) blurred and noisy images. One may, then, envision a scenario where a set of LR images is acquired with a sensor on a moving platform. In such a case, an SR image can be reconstructed in an area of sufficient overlap between the LR images which generally have a relative shift with respect to each other by subpixel amounts. The visual quality of the SR image is affected by many factors such as the optics blur, the inherent signalto- noise ratio of …

Attracting K-12 Students Towards Engineering Disciplines With Project Based Learning Modules, Alok K. Verma

Engineering Technology Faculty Publications

Low enrollment and high attrition rates in Science, Technology, Engineering and Math (STEM) based degree programs have created a workforce problem in industries like shipbuilding and repair which are important for national security. Part of this problem can be attributed to pedagogical issues like lack of engaging hands-on activities utilized for science and math education in middle and high schools. Lack of student interest in technical careers can also be attributed to lack of an integrated approach in teaching math, science and technical education. To engage student's interest in the technical career path, it is important that students establish a …

Reactivation Of A Six-Degree-Of-Freedom Repeated Impact Machine Using Programmable Logical Controller (Plc), Cheng Lin

Engineering Technology Faculty Publications

Reactivation of a six-degree-of-freedom impact machine using Programmable Logical Control (PLC) is presented. The output from the machine is the history of accelerations collected from accelerometers attached at the testing article and a load cell mounted at the rubber pad where the impact occurs. Readings of the acceleration and impact force are sent to a PC for analysis through a data acquisition device (USB 6251) and Labview software provided by National Instrument (NI). Result shows that the machine can repeatedly generate an impact force up to eleven Gs. Demonstration of the project can be used as one of labs in …

Parallel-Sparse Symmetrical/Unsymmetrical Finite Element Domain Decomposition Solver With Multi-Point Constraints For Structural/Acoustic Analysis, Siroj Tungkahotara, Willie R. Watson, Duc T. Nguyen, Subramaniam D. Rajan

Civil & Environmental Engineering Faculty Publications

Details of parallel-sparse Domain Decomposition (DD) with multi-point constraints (MPC) formulation are explained. Major computational components of the DD formulation are identified. Critical roles of parallel (direct) sparse and iterative solvers with MPC are discussed within the framework of DD formulation. Both symmetrical and unsymmetrical system of simultaneous linear equations (SLE) can be handled by the developed DD formulation. For symmetrical SLE, option for imposing MPC equations is also provided.

Large-scale (up to 25 million unknowns involving complex numbers) structural and acoustic Finite Element (FE) analysis are used to evaluate the parallel computational performance of the proposed DD implementation using …

Scaling Properties At Freeze-Out In Relativistic Heavy-Ion Collisions, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration

Physics Faculty Publications

Identified charged pion, kaon, and proton spectra are used to explore the system size dependence of bulk freeze-out properties in Cu+Cu collisions at √sNN=200 and 62.4 GeV. The data are studied with hydrodynamically motivated blast-wave and statistical model frameworks in order to characterize the freeze-out properties of the system. The dependence of freeze-out parameters on beam energy and collision centrality is discussed. Using the existing results from Au + Au and pp collisions, the dependence of freeze-out parameters on the system size is also explored. This multidimensional systematic study furthers our understanding of the QCD phase diagram revealing the importance …

Delayed-Bang Approach Towards More Sustainable Critical Infrastructure Risk Management, C. Ariel Pinto, Michael K. Mcshane, Abhishek S. Pathak

Finance Faculty Publications

This article describes the Delayed Bang Approach for determining the value of risk management alternatives in critical infrastructure security. The discussion includes (1) the need for sustainable risk management (2) the importance of time valuation in evaluating competing loss prevention and loss reduction alternatives, (3) the convergence of deterministic engineering economics, survivability analysis, and probabilistic analysis, and (4) hypothetical examples of the Delayed-Bang Approach and significance towards more sustainable risk management.

Primary And Secondary Incident Management: Predicting Durations In Real Time, Asad J. Khattak, Xin Wang, Hongbing Zhang, Mecit Cetin

Civil & Environmental Engineering Faculty Publications

Traffic incidents are a major source of congestion in Virginia. Secondary incidents comprise a relatively small but important portion of all incidents, and relatively little is known about their occurrence, characteristics, and associated delays. The main objectives of this study were to define secondary incidents, understand and analyze the occurrence and nature of such incidents, and develop tools that can comprehensively and continuously analyze primary and secondary incidents at the planning and operational levels, ultimately contributing to congestion management. The scope of the study is limited to freeway incidents in the Hampton Roads (HR) area. The study found that secondary …

Eeg Artifact Removal Using A Wavelet Neural Network, Hoang-Anh T. Nguyen, John Musson, Jiang Li, Frederick Mckenzie, Guangfan Zhang, Roger Xu, Carl Richey, Tom Schnell, Thomas E. Pinelli (Ed.)

Electrical & Computer Engineering Faculty Publications

In this paper we developed a wavelet neural network. (WNN) algorithm for Electroencephalogram (EEG) artifact removal without electrooculographic (EOG) recordings. The algorithm combines the universal approximation characteristics of neural network and the time/frequency property of wavelet. We compared the WNN algorithm with the ICA technique and a wavelet thresholding method, which was realized by using the Stein's unbiased risk estimate (SURE) with an adaptive gradient-based optimal threshold. Experimental results on a driving test data set show that WNN can remove EEG artifacts effectively without diminishing useful EEG information even for very noisy data.

A Systematic Approach For Engagement Analysis Under Multitasking Environments, Guangfan Zhang, John Leddo, Roger Xu, Carl Richey, Tom Schnell, Frederick Mckenzie, Jiang Li, Thomas E. Pinelli (Ed.)

Electrical & Computer Engineering Faculty Publications

An overload condition can lead to high stress for an operator and further cause substantial drops in performance. On the other extreme, in automated systems, an operator may become underloaded; in which case, it is difficult for the operator to maintain sustained attention. When an unexpected event occurs, either internal or external to the automated system, a disengaged operation may neglect, misunderstand, or respond slowly/inappropriately to the situation. In this paper, we discuss a systematic approach monitor for extremes of cognitive workload and engagement in multitasking environments. Inferences of cognitive workload and engagement are based on subjective evaluations, objective performance …

Prediction Of Brain Tumor Progression Using Multiple Histogram Matched Mri Scans, Debrup Banerjee, Loc Tran, Jiang Li, Yuzhong Shen, Frederic Mckenzie, Jihong Wang, Ronald M. Summers (Ed.), Bram Van Ginneken (Ed.)

Electrical & Computer Engineering Faculty Publications

In a recent study [1], we investigated the feasibility of predicting brain tumor progression based on multiple MRI series and we tested our methods on seven patients' MRI images scanned at three consecutive visits A, B and C. Experimental results showed that it is feasible to predict tumor progression from visit A to visit C using a model trained by the information from visit A to visit B. However, the trained model failed when we tried to predict tumor progression from visit B to visit C, though it is clinically more important. Upon a closer look at the MRI scans …