Engineering Commons^™

Ultrafast Decay Of Hot Phonons In An Algan/Aln/Algan/Gan Camelback Channel, J. H. Leach, M. Wu, H. Morkoç, J. Liberis, E. Šermukšnis, M. Ramonas, A. Matulionis

Electrical and Computer Engineering Publications

A bottleneck for heat dissipation from the channel of a GaN-based heterostructure field-effect transistor is treated in terms of the lifetime of nonequilibrium (hot) longitudinal optical phonons, which are responsible for additional scattering of electrons in the voltage-biased quasi-two-dimensional channel. The hot-phonon lifetime is measured for an Al_0.33Ga_0.67N/AlN/Al_0.1Ga_0.9N/GaN heterostructure where the mobile electrons are spread in a composite Al_0.1Ga_0.9N/GaN channel and form a camelback electron density profile at high electric fields. In accordance with plasmon-assisted hot-phonon decay, the parameter of importance for the lifetime is not the total …

Field-Assisted Emission In Algan/Gan Heterostructure Field-Effect Transistors Using Low-Frequency Noise Technique, Cemil Kayis, C. Y. Zhu, Mo Wu, X. Li, Ümit Özgür, Hadis Morkoç

Electrical and Computer Engineering Publications

We utilized low-frequency noise measurements to probe electron capture and emission from the traps in AlGaN/GaN heterostructurefield-effect transistors as a function of drain bias. The excess noise-spectra due to generation-recombination effect shifted higher in frequency with the elevated temperature from room temperature up to 446 K. These temperature dependent noise measurements were carried out for four different drain-bias values from 4 up to 16 V with 4 V increments. The shift of the excess-noise in frequency was also seen with increasing drain bias. The characteristic recharging times for the trapped electrons varied within the range of 26 μs − …

Charge Storage Characteristics Of Ultra-Small Pt Nanoparticle Embedded Gaas Based Non-Volatile Memory, Reginald Jeff, M Yun, B Ramalingam, B Lee, V Misra, Gregory Edward Triplett, Shubhra Gangopadhyay

Electrical and Computer Engineering Publications

Charge storage characteristics of ultra-small Pt nanoparticle embedded devices were characterized by capacitance-voltage measurements. A unique tilt target sputtering configuration was employed to produce highly homogenous nanoparticle arrays. Pt nanoparticle devices with sizes ranging from ∼0.7 to 1.34 nm and particle densities of ∼3.3–5.9 × 1012 cm−2 were embedded between atomic layer deposited and e-beam evaporated tunneling and blocking Al2O3 layers. These GaAs-based non-volatile memory devices demonstrate maximum memory windows equivalent to 6.5 V. Retention characteristics show that over 80% charged electrons were retained after 105 s, which is promising for device applications.

Reduced Auger Recombination In Mid-Infrared Semiconductor Lasers, Robert Bedford, Gregory Edward Triplett, David H. Tomich, Stephan W. Koch, Jerome Moloney, Jorg Hader

Electrical and Computer Engineering Publications

A quantum-design approach to reduce the Auger losses in two micron InGaSb type-I quantum well edge-emitting lasers is reported. Experimentally realized structures show a 3X reduction in the threshold, which results in 4.6 lower Auger current loss at room temperature. This is equivalent to a carrier lifetime improvement of 5.7 and represents about a 19-fold reduction in the equivalent “Auger coefficient.”

Performance And Memory Space Optimizations For Embedded Systems, Taylan Yemliha

Electrical Engineering and Computer Science - Dissertations

Embedded systems have three common principles: real-time performance, low power consumption, and low price (limited hardware). Embedded computers use chip multiprocessors (CMPs) to meet these expectations. However, one of the major problems is lack of efficient software support for CMPs; in particular, automated code parallelizers are needed.

The aim of this study is to explore various ways to increase performance, as well as reducing resource usage and energy consumption for embedded systems. We use code restructuring, loop scheduling, data transformation, code and data placement, and scratch-pad memory (SPM) management as our tools in different embedded system scenarios. The majority of …

Conditional Posterior Cramer-Rao Lower Bound And Distributed Target Tracking In Sensor Networks, Long Zuo

Electrical Engineering and Computer Science - Dissertations

Sequential Bayesian estimation is the process of recursively estimating the state of a dynamical system observed in the presence of noise. Posterior Cramer-Rao lower bound (PCRLB) sets a performance limit onany Bayesian estimator for the given dynamical system. The PCRLBdoes not fully utilize the existing measurement information to give anindication of the mean squared error (MSE) of the estimator in the future. In many practical applications, we are more concerned with the value of the bound in the future than in the past. PCRLB is an offline bound, because it averages out the very useful measurement information, which makes it …

The Differential Scheme And Quantum Computation, Robert J. Irwin

Electrical Engineering and Computer Science - Dissertations

It is well-known that standard models of computation are representable as simple dynamical systems that evolve in discrete time, and that systems that evolve in continuous time are often representable by dynamical systems governed by ordinary differential equations. In many applications, e.g., molecular networks and hybrid Fermi-Pasta-Ulam systems, one must work with dynamical systems comprising both discrete and continuous components.

Reasoning about and verifying the properties of the evolving state of such systems is currently a piecemeal affair that depends on the nature of major components of a system: e.g., discrete vs. continuous components of state, discrete vs. continuous time, …

Correlated Sources In Distributed Networks - Data Transmission, Common Information Characterization And Inferencing, Wei Liu

Electrical Engineering and Computer Science - Dissertations

Correlation is often present among observations in a distributed system. This thesis deals with various design issues when correlated data are observed at distributed terminals, including: communicating correlated sources over interference channels, characterizing the common information among dependent random variables, and testing the presence of dependence among observations.

It is well known that separated source and channel coding is optimal for point-to-point communication. However, this is not the case for multi-terminal communications. In this thesis, we study the problem of communicating correlated sources over interference channels (IC), for both the lossless and the lossy case. For lossless case, a sufficient …

Noise-Enhanced And Human Visual System-Driven Image Processing: Algorithms And Performance Limits, Renbin Peng

Electrical Engineering and Computer Science - Dissertations

This dissertation investigates the problem of image processing based on stochastic resonance (SR) noise and human visual system (HVS) properties, where several novel frameworks and algorithms for object detection in images, image enhancement and image segmentation as well as the method to estimate the performance limit of image segmentation algorithms are developed.

Object detection in images is a fundamental problem whose goal is to make a decision if the object of interest is present or absent in a given image. We develop a framework and algorithm to enhance the detection performance of suboptimal detectors using SR noise, where we add …

Electrochemical Investigation Of Chromium Nanocarbide Coated Ti-6al-4v And Co-Cr-Mo Alloy Substrates, Viswanathan Swaminathan, Haitong Zeng, Daniel Lawrynowicz, Zongtao Zhang, Jeremy L. Gilbert

Biomedical and Chemical Engineering - All Scholarship

This study investigated the electrochemical behavior of chromium nano-carbide cermet coating applied on Ti–6Al–4V and Co–Cr–Mo alloys for potential application as wear and corrosion resistant bearing surfaces. The cermet coating consisted of a highly heterogeneous combination of carbides embedded in a metal matrix. The main factors studied were the effect of substrate (Ti–6Al–4V vs. Co–Cr–Mo), solution conditions (physiological vs. 1 M H₂O₂ of pH 2), time of immersion (1 vs. 24 h) and post coating treatments (passivation and gamma sterilization). The coatings were produced with high velocity oxygen fuel (HVOF) thermal spray technique at atmospheric conditions to …

Mode I Delamination Fracture Characterization Of Polymeric Composites Under Elevated Temperature, Wenming Zhao

Mechanical and Aerospace Engineering - Dissertations

Delamination is one of the major failure modes seen in the laminated polymeric matrix composite (PMC). Accurate prediction of delamination initiation and propagation is important for the design and analysis of robust composite structures. Existing experimental methodologies that are based on linear elastic fracture mechanics are inadequate to characterize delamination fracture properties under elevated temperature when PMC properties become time-, loading-history, and rate-dependent. A new experimental methodology based on linear viscoelastic fracture theory is developed and verified through finite element analysis and experiments. This new technique determines crack growth curves, such as stress intensity factor vs. crack growth speed and …

A Detailed And Systematic Investigation Of Personal Ventilation Systems, Jackie Russo

Mechanical and Aerospace Engineering - Dissertations

This research investigates the use of personal ventilation (PV) in a typical office space as a means of contaminant removal from ones breathing zone (BZ). For this work, a validated computational model was developed and used for PV assessment under different scenarios. Experimental data of Khalifa et al. (2009), Ito (2007) and Rim et al. (2009) were used to validate a computational model that is capable of simulating indoor chemical reactions with excellent agreement compared with the experiments. Through the validation process, various computational parameters were determined to be significant for producing accurate results. Grid resolution, geometry, far field BCs, …

Santa Clara Magazine, Volume 52, Number 3, Winter 2010, Santa Clara University

Santa Clara Magazine

14 - GOOD LIT By Alicia K. Gonzales '09 and Steven Boyd Saum. It's time to light 10 candles on the birthday cake for SCU's California Legacy Series. To date: 43 books, 500 radio broadcasts, and a handful of movies. What's next? Something big.

16 - SHAPING THE FUTURE by Adolfo Nicolas, S.J. What can Jesuit universities do-together-to make the world a more humane, just, and sustainable place? It starts with imagination, an unequaled global network, and a conference in Mexico City- where Jesuit Superior General Adolfo Nicolas takes stock of challenges to Jesuit higher education today.

24 - A …

Leveraging Multi-User Diversity, Channel Diversity And Spatial Reuse For Efficient Scheduling In Wireless Relay Networks, Shen Wan, Jian Tang, Brendan Mumey, Richard S. Wolff, Weiyi Zhang

Electrical Engineering and Computer Science - All Scholarship

Relay stations can be deployed in a wireless network to extend its coverage and improve its capacity. In this paper, we study a scheduling problem in OFDMA-based wireless relay networks with consideration for multi-user diversity, channel diversity and spatial reuse. First, we present a Mixed Integer Linear Programming (MILP) formulation to provide optimum solutions. It has been shown by previous research that performance of a wireless scheduling algorithm is usually related to the interference degree δ, which is the maximum number of links that interfere with a common link but do not interfere with each other. Therefore, we then show …

Augmented Lagrangian Approach To Design Of Structured Optimal State Feedback Gains, Fu Lin, Makan Fardad, Mihailo R. Jovanovic

Electrical Engineering and Computer Science - All Scholarship

We consider the design of optimal state feedback gains subject to structural constraints on the distributed controllers. These constraints are in the form of sparsity requirements for the feedback matrix, implying that each controller has access to information from only a limited number of subsystems. The minimizer of this constrained optimal control problem is sought using the augmented Lagrangian method. Notably, this approach does not require a stabilizing structured gain to initialize the optimization algorithm. Motivated by the structure of the necessary conditions for optimality of the augmented Lagrangian, we develop an alternating descent method to determine the structured optimal …

Minimax Games For Cooperative Spectrum Sensing In A Centralized Cognitive Radio Network In The Presence Of Interferers, Venkata Sriram Siddhardh Nadendla, Hao Chen, Pramod Varshney

Electrical Engineering and Computer Science - All Scholarship

In this paper, we consider the problem of interference attacks for cooperative spectrum sensing in a centralized cognitive radio network comprising N cognitive radios (CRs) and one fusion center (FC) in the presence of a fixed interferer. The design metric chosen is the error probability. We prove the existence of a saddle-point in the minimax game between the interferer and the CR network. An optimal solution is found that maximizes the objective with respect to the interferer’s parameters and minimizes the same with respect to the CR network’s parameters. We show that the probability of error is a quasi-convex function …

Attacks On Webview In The Android System, Tongbo Luo, Hao Hao, Wenliang Du, Heng Yin

Electrical Engineering and Computer Science - All Scholarship

WebView is an essential component in both Android and iOS platforms, enabling smartphone and tablet apps to embed a simple but powerful browser inside them. To achieve a better interaction between apps and their embedded\browsers", WebView provides a number of APIs, allowing code in apps to invoke and be invoked by the JavaScript code within the web pages, intercept their events, and modify those events. Using these features, apps can become customized \browsers" for their intended web applications. Currently, in the Android market, 86 percent of the top 20 most downloaded apps in 10 diverse categories use WebView. The design …

A Financial Impact Assessment Of Ld 1725: Stream Crossings (Presentation), New England Environmental Finance Center, Muskie School Of Public Service

Water

This report looks at the potential financial impact of LD 1725 on the estimated 30,000 stream crossings in the State of Maine that would be affected by the law. Our research for this report included the analysis of nearly 2000 stream crossings and the data collection necessary for the development of extensive stream crossing replacement cost models. We found that the 1.2 bankfull requirements in LD 1725 would result in a 75% ‐ 250% increase in structure widths for stream crossing projects across the state. An upsize of this magnitude would increase the cost of replacing stream crossings statewide by …

Freeing Space For Nasa: Incorporating A Lossless Compression Algorithm Into Nasa's Fiber Optic Strain Sensing System, Kaitlyn Fiechtner, Allen Parker

STAR Program Research Presentations

NASA’s Fiber Optic Strain Sensing (FOSS) system can gather and store up to 1,536,000 bytes (1.46 megabytes) per second. Since the FOSS system typically acquires hours—or even days—of data, the system can gather hundreds of gigabytes of data for a given test event. To store such large quantities of data more effectively, NASA is modifying a Lempel-Ziv-Oberhumer (LZO) lossless data compression program to compress data as it is being acquired in real time. After proving that the algorithm is capable of compressing the data from the FOSS system, the LZO program will be modified and incorporated into the FOSS system. …

The Influence Of Interleukin-4 On Ligament Healing, Connie S. Chamberlain, Ellen M. Leiferman, Kayt E. Frisch, Sijian Wang, Xipei Yang, Stacey L. Brickson, Ray Vanderby

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Despite a complex cascade of cellular events to reconstruct the damaged extracellular matrix, ligament healing results in a mechanically inferior scarred ligament. During normal healing, granulation tissue expands into any residual normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise and an inefficient repair process. To control creeping substitution and possibly enhance the repair process, the antiinflammatory cytokine, interleukin-4 (IL-4), was administered to rats before and after rupture of their medial collateral ligaments. In vitro experiments showed a time-dependent effect on fibroblast proliferation after IL-4 treatment. In vivo treatments with IL-4 (100 ng/mL IV) …

Terminal Guidance Of Autonomous Parafoils In High Wind-To-Airspeed Ratios, Nathan Slegers, O A. Yakimenko

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Autonomous precision placement of parafoils is challenging because of their limited control authority and sensitivity to winds. In particular, when wind speed is near the airspeed, guidance is further complicated by the parafoils inability to penetrate the wind. This article specifically addresses the terminal phase and develops an approach for generating optimal trajectories in real-time based on the inverse dynamics in the virtual domain. The method results in efficient solution of a two-point boundary-value problem using only a single optimization parameter allowing the trajectory to be generated at a high rate, mitigating effects of the unknown winds. It is shown …

A Method For Defining Wind Turbine Setback Standards, Jonathan Rogers, Nathan Slegers, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Setback distances established by regulatory authorities to minimize the probability of blade fragment impact with roads, structures and infrastructure can often have a significant impact on wind farm development. However, these minimum distance requirements typically rely on arbitrary rules of thumb and are not based on a physical or probabilistic analysis of blade throw. The work reported here uses a probabilistic approach to evaluate the effectiveness of current standards and to propose a new technique for determining setback distances. This is accomplished through the use of a dynamic model of wind turbine blade failure coupled with Monte Carlo simulation techniques …

Techniques From Workshops On Teaching: Implementing The Concepts And Evaluating Our Approaches, Michael R. Foster, Justin R. Vander Werff

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

The challenges for new engineering educators abound and there are never enough hours in a day or days in a week. Young educators may lack confidence in course subject material given that they have never taught (the topic and/or in a classroom) before. In addition, their knowledge of teaching pedagogy and classroom management strategies often lacks refinement since their education is almost exclusively in a field of engineering rather than education. Teaching workshops have been developed to expose instructors in higher education to practical teaching pedagogy and effective classroom management. These workshops often emphasize research-based methods including use of clearly …

Tethered Aerostat Modeling Using An Efficient Recursive Rigid-Body Dynamics Approach, Brad Hembree, Nathan Slegers

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

A tethered aerostat model is developed using a computationally efficient recursive tether model. The recursive rigid-body tether model results in unconstrained ordinary differential equations and maintains much of the simplicity of simple lumped-mass tether models, while avoiding numerical difficulties associated with using many stiff elastic elements with low mass. Further efficiency is achieved by treating each tether link as a body of revolution and assuming that tether spin is negligible to the dynamics. The tether is attached to a six-degree-of-freedom aerostat model using a single viscoelastic element. The final recursive tethered aerostat model is well suited for a variety of …

Ultrasound Echo Is Related To Stress And Strain In Tendon, Sarah Duenwald, Hirohito Kobayashi, Kayt E. Frisch, Roderic Lakes, Ray Vanderby Jr.

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

The mechanical behavior of tendons has been well studied in vitro. A noninvasive method to acquire mechanical data would be highly beneficial. Elastography has been a promising method of gathering in vivo tissue mechanical behavior, but it has inherent limitations. This study presents acoustoelasticity as an alternative ultrasound-based method of measuring tendon stress and strain by reporting a relationship between ultrasonic echo intensity (B-mode ultrasound image brightness) and mechanical behavior of tendon in vitro. Porcine digital flexor tendons were cyclically loaded in a mechanical testing system while an ultrasonic echo response was recorded. We report that echo intensity …

A Financial Impact Assessment Of Ld 1725: Stream Crossings Presentation, New England Environmental Finance Center

Economics and Finance

This report looks at the potential financial impact of LD 1725 on the estimated 30,000 stream crossings in the State of Maine that would be affected by the law. Our research for this report included the analysis of nearly 2000 stream crossings and the data collection necessary for the development of extensive stream crossing replacement cost models. We found that the 1.2 bankfull requirements in LD 1725 would result in a 75% ‐ 250% increase in structure widths for stream crossing projects across the state. An upsize of this magnitude would increase the cost of replacing stream crossings statewide by …

Eating Rate During A Fixed-Portion Meal Does Not Affect Postprandial Appetite And Gut Peptides Or Energy Intake During A Subsequent Meal, J. Phillip Karl, Andrew J. Young, Scott J. Montain

United States Army: Publications

Eating rate has recently been shown to influence energy intake and appetite during an ad libitummeal, and alter postprandial secretion of glucagon-like peptide-1 (GLP-1) and peptide-YY (PYY) following a fixed-portionmeal. Whether these effects influence satiety, as measured by energy intake at the subsequent meal, is unclear. We manipulated eating rate during a fixed-portion meal in order to examine how eating behavior and associated periprandial and postprandial responses of putative endocrine mediators of appetite would affect energy intake at the following meal in fifteen non-obese (BMI ≥ 25 kg/m²) and ten obese (BMI ≥ 30 kg/m²) healthy adult men and …

Effects Of Gage Length, Loading Rates, And Damage On The Strength Of Ppta Fibers, Jaeyoung Lim, James Q. Zheng, Karl Masters, Weinong W. Chen

United States Army: Publications

Axial tension and transverse compression experiments on single fibers were performed to investigate the mechanical behavior of three high-performance fibers (Kevlar ®, Kevlar ® 129, and Twaron ®) with diameters in the order of 9-12 μm. The single fibers were manufactured from 1998 through 2008. A miniaturized tensile Kolsky bar was used to determine the tensile response of PPTA single fibers at a high strain rate. Gage length and strain rate were found to have minimum effects on the tensile strength of PPTA single fibers. Manufacturing time over a decade was found to have negligible effects on the tensile strength …

Recombinant Paraoxonase 1 Protects Against Sarin And Soman Toxicity Following Microinstillation Inhalation Exposure In Guinea Pigs, Manojkumar Valiyaveettil, Yonas Alamneh, Peter Rezk, Michael W. Perkins, Alfred M. Sciuto, Bhupendra P. Doctor, Madhusoodana P. Nambiar

United States Army: Publications

To explore the efficacy of paraoxonase 1 (PON1) as a catalytic bioscavenger, we evaluated human recombinant PON1 (rePON1) expressed in Trichoplusia ni larvae against sarin and soman toxicity using microinstillation inhalation exposure in guinea pigs. Animals were pretreated intravenously with catalytically active rePON1, followed by exposure to 1.2 X LCt₅₀ sarin or soman. Administration of 5 units of rePON1 showed mild increase in the blood activity of the enzyme after 30 min, but protected the animals with a significant increase in survival rate along with minimal signs of nerve agent toxicity. Recombinant PON1 pretreated animals exposed to sarin or …

Fluidized Bed Pyrolysis Of Lignin In A Bubbling Bed Reactor, Pietro Palmisano, Valentina Lago, Franco Berruti, Cedric Briens

Bioenergy III: Present and New Perspectives on Biorefineries

No abstract provided.