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Silicon Dioxide-Encapsulated High-Voltage Algan/Gan Hfets For Power-Switching Applications, N. Tipirneni, V. Adivarahan, Grigory Simin, Asif Khan

Faculty Publications

In this letter, new approach in achieving high breakdown voltages in AlGan/GaN heterostructure field-effect transistors (HFETs) by suppressing surface flashover using solid encapsulation material is presented. Surface flashover in III-Nitride-based HFETs limits the operating voltages at levels well below breakdown voltages of GaN. This premature gate-drain breakdown can be suppressed by immersing devices in high-dielectric-strength liquids (e.g., Fluorinert); however, such a technique is not practical. In this letter, AlGan/GaN HFETs encapsulated with PECVD-deposited SiO2 films demonstrated breakdown voltage of 900 V, very similar to that of devices immersed in Fluorinert liquid. Simultaneously, low dynamic ON-resistance of 2.43 m Omega. cm(2) …

Comparative Study Of Aerodynamic Interference During Aft Dispense Of Munitions, Matthew G. Burkinshaw

Theses and Dissertations

Based on forthcoming USAF needs, an investigation was launched to further the understanding of aft dispense of munitions in a high-speed environment. A computational fluid dynamics (CFD) study was performed followed by a wind tunnel experiment. The study consisted of a strut-mounted cone simulating a parent vehicle and a sting mounted cone-cylinder store situated directly behind the cone. The CFD modeled the test objects inside a supersonic wind tunnel in which the experiments took place. The CFD study consisted of evaluating a new strut designed to reduce asymmetry in the airflow aft of the cone. The CFD study also included …

Radar Orbit Analsis Tool Using Least Squares Estimator, Sandra M. Rashash

Theses and Dissertations

Most objects tracked in space follow a regular Keplerian orbit; unfortunately, non-Keplerian objects such as maneuvering satellites, tethered systems, and thrusting ballistic missiles are becoming more common. It is important to be able to distinguish between Keplerian and non-Keplerian objects due to the potential risk of a tethered satellite being mistaken for an object on re-entry. This research focused on creating a computer model that can detect the non-gravitational acceleration present in non-Keplerian orbits. A 3rd order Taylor series expansion was used to model the dynamics and to produce simulated radar data. Linear least squares estimation was used to estimate …

Navigation Using Orthogonal Frequency Division Multiplexed Signals Of Opportunity, Jamie S. Velotta

Theses and Dissertations

The global positioning system (GPS) provides high-accuracy position measurements anywhere in the world. However, a limitation of this system is that a line of sight to multiple satellites is required; therefore, it is unsuitable to use indoors or in urban canyons. Also, in the presence of radio-frequency interference or jamming, GPS may be unavailable. Alternative methods of navigation and positioning are need to either compliment GPS as a backup or for use in areas unreachable by satellites. This research analyzes a feature-based correlation approach for determining reception differences between two Orthogonal Frequency Division receivers for the purpose of TDOA calculations. …

Measurement And Analysis Of The Shocks Generated During Egg Production, Jay A. Singh, Chris Ferrier, Paul Singh

Industrial Technology and Packaging

In their journey from the laying cage to shipments out of an egg production operation, table eggs encounter multiple shock events. While all agricultural commodities run the possibility of damage during the course of production, shell eggs are particularly susceptible to being cracked or broken during the production operation. A typical egg production facility experiences 2% to 7% checks (a partial mechanical failure to the egg shell) during handling, packaging and transportation of shell eggs. It has been estimated that the total losses to the U.S. egg industry due to checks and breakage of eggs during production amounts to over …

Development Of Wholesale Packaging To Prevent Post-Harvest Damage To Rose Apples, Bundit Jarimopas, Siam Toomsaengtong, Sher Paul Singh, Jay Singh, Rangsinee Sothornvit

Industrial Technology and Packaging

The purpose of this research was to determine post-harvest damage to rose apples due to transportation hazards and to comparatively evaluate the performance of the current and proposed wholesale packaging for the fruit. The methodology comprised of sampling and conducting damage analysis of rose apples of two varieties (Thongsamsri and Toonklao) distributed using commercial packaging to various retailers and wholesalers selected at random around the Bangkok metropolitan areas. Three kinds of current wholesale packaging were packed with newly harvested, damage-free, and uniform sized Thongsamsri rose apples and tested using a vibration simulator. The same testing was performed for the two …

Comparison Of Package Cushioning Materials To Protect Post-Harvest Impact Damage To Apples, Bundit Jarimopas, Sher Paul Singh, S. Sayasoonthorn, Jay A. Singh

Industrial Technology and Packaging

Damage to fruits and vegetables continues to be a big challenge as global markets become a reality. Worldwide distribution of sensitive produce is faced with various levels of impacts from shipping and handling. Despite a variety of packaging options available today, bruising damage is commonplace for post-harvest apples throughout the supply chain. The major sources of bruising are compression, impact or vibration forces. Understanding where these forces occur can help reduce this type of mechanical damage to apples. The purpose of this study was to investigate the impact characteristics of foam net and corrugated board when applied as wrapping for …

Assessing Capacity Scalability Policies In Rms Using System Dynamics, Ahmed M. Deif, Hoda A. Elmaraghy

Industrial Technology and Packaging

This paper presents a model for assessing different capacity scalability policies in Reconfigurable Manufacturing System (RMS) for different changing demand scenarios. The novelty of this approach is two fold: (1) it is the first attempt to explore different capacity scalability policies in RMS based on multiple performance measures, mainly scaling rate, Work In Process level, inventory level and backlog level; and (2) the dynamic scalability process in RMS is modeled for the first time using System Dynamics. Different policies for capacity scalability for various demand scenarios were assessed. Numerical simulation results obtained using the developed capacity scalability model showed that …

Unreliable Retrial Queues In A Random Environment, James D. Cordeiro Jr.

Theses and Dissertations

This dissertation investigates stability conditions and approximate steady-state performance measures for unreliable, single-server retrial queues operating in a randomly evolving environment. In such systems, arriving customers that find the server busy or failed join a retrial queue from which they attempt to regain access to the server at random intervals. Such models are useful for the performance evaluation of communications and computer networks which are characterized by time-varying arrival, service and failure rates. To model this time-varying behavior, we study systems whose parameters are modulated by a finite Markov process. Two distinct cases are analyzed. The first considers systems with …

Common Aero Vehicle Autonomous Reentry Trajectory Optimization Satisfying Waypoint And No-Fly Zone Constraints, Timothy R. Jorris

Theses and Dissertations

To support the Global Strike mission, an autonomous trajectory optimization technique is presented to minimize the flight time, satisfy terminal and intermediate constraints, and remain within the specified vehicle heating and control limitations. "Waypoints" are specified for reconnaissance or multiple payload deployments and "no-fly zones" are specified for geopolitical restrictions or threat avoidance. The Hypersonic Cruise Vehicle (HCV) is used as a simplified two-dimensional platform to compare multiple solution techniques. The solution techniques include a unique geometric approach, an analytical dynamic optimization technique, and a numerical approach. This numerical technique is a direct solution method involving pseudospectral methods and nonlinear …

Validation Of The Afit Small Scale Combustion Facility And Oh Laser-Induced Fluorescence Of An Atmospheric Laminar Premiext Ed Flame, Stephen J. Koether

Theses and Dissertations

Construction in the AFIT combustion facility is complete and the objective of this report is to explain the steps taken to make the laboratory operational. The infinite radius Ultra-Compact Combustor (UCC) sectional model has been delivered and is fully installed with all fuel, air and instrument lines. Every major system in the lab has been tested and is functioning properly. Laboratory operating procedure has been established to ensure both safety and continuity in experimental results. Finally, the lab has been certified through official safety channels and combustion experiments are underway. The unique capability of the AFIT combustion laboratory is the …

Cyclic Creep And Recovery Behavior Of Nextel™ 720/Alumina Ceramic Matrix Composite At 1200° C In Air And Steam Environments, Bridgett A. Whiting

Theses and Dissertations

The cyclic creep and recovery behaviors of the N720/Al₂O₃ composite were investigated in this research. The ceramic matrix composite (CMC) contains a porous alumina matrix with laminated, woven mullite/alumina (Nextel^TM 720) fibers. The composite does not have an interface between the fiber and matrix. The CMC relies on the porous nature for flaw tolerance. The objective of this study the influences of monotonic creep and cyclic creep loading histories on the creep lifetime, creep strain rate, accumulated creep strain as well as on the recovery of creep strain at near zero stress. The cyclic creep and …

Conceptual Mems Devices For A Redeployable Antenna, Virginia Miller

Theses and Dissertations

Micro-Electro-Mechanical Systems (MEMS) are becoming an integral part of our lives through a wide range of applications, including MEMS accelerators for air bag deployment in vehicles, micromirrors in projection devices, and various sensors for chemical/biological applications. MEMS are a key aspect of ever-increasing significance in a myriad of commercial and military applications. Because of this importance, this thesis utilizes MEMS devices that can deploy and retract an antenna suitably sized for placement on an insect or microrobot for communication purposes. A target monopole antenna with a length of 1 mm was used as a test metric. From this requirement, several …

Urban Particulate Matter Casues Er Stress And The Unfolded Protein Response In Human Lung Cells, T. L. Watterson, B. Hamilton, Randy S. Martin, R. A. Coulombe Jr.

Civil and Environmental Engineering Faculty Publications

Because of its presumed adverse health effects, particulate air pollution (PM) has received growing attention, but the cellular mechanisms by which PM exerts toxicity are not well elucidated. PM has been associated with early mortality from illnesses that share endoplasmic reticulum (ER) stress as a mechanism of pathogenesis. In this study, we examined whether PM would induce the unfolded protein response (UPR) which is a cellular response to ER stress. Coarse (PM10) and fine (PM2.5) PM was collected from a single location in Northern Utah's Cache Valley during atmospheric inversions occurring in January 2002 and January 2003. Extracts of PM …

Effects Of Pm2.5 Collected From Cache Valley, Ut On Genes Associated With The Inflammatory Response In Human Lung Cells, T L. Watterson, J. Sorensen, Randy S. Martin, R. A. Coulombe Jr.

Civil and Environmental Engineering Faculty Publications

In January 2004, the normally picturesque Cache Valley in northern Utah made national headlines with the highest PM2.5 levels in the nation. Epidemiological studies linked exposure to particulate air pollution in other locations with stroke and Alzheimer's disease and to early mortality from all causes, cancer, and cardiopulmonary diseases. To determine potential effects of these particles on human health, human bronchial epithelial cells (BEAS-2B) were cultured with PM2.5collected from various locations in the Cache Valley. These particles were slightly cytotoxic, but more potent than NH4NO3, the major chemical component of Cache Valley PM2.5. Gene expression analysis of PM2.5-exposed cells was …

Ontology-Enriched Semantic Space For Video Search, Xiao-Yong Wei, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

Multimedia-based ontology construction and reasoning have recently been recognized as two important issues in video search, particularly for bridging semantic gap. The lack of coincidence between low-level features and user expectation makes concept-based ontology reasoning an attractive midlevel framework for interpreting high-level semantics. In this paper, we propose a novel model, namely ontology-enriched semantic space (OSS), to provide a computable platform for modeling and reasoning concepts in a linear space. OSS enlightens the possibility of answering conceptual questions such as a high coverage of semantic space with minimal set of concepts, and the set of concepts to be developed for …

Insults In Your Inbox, M. Thulasidas

Research Collection School Of Computing and Information Systems

Email is a boon at work, but aggressive staff may use it to inflict humiliation. Most of its impact has been positive. An email from the big boss to all@yourcompany, for instance, is a fair substitute for a general communication meet- ing. In smaller teams, email often saves meetings and increases productivity.

A Light-Weight Event-Driven Protocol For Sensor Clustering In Wireless Camera Networks, Henry Medeiros, Johnny Park, Avinash Kak

Electrical and Computer Engineering Faculty Research and Publications

We propose a light-weight event-driven protocol for wireless camera networks to allow for formation and propagation of clusters of cameras for the purpose of collaborative processing during object tracking. Cluster formation is triggered by the detection of objects with specific features. Our protocol allows for simultaneous formation and propagation of multiple clusters. Cameras being directional devices, more than one cluster may track a single object since groups of cameras outside each others communication range may see the same object. Entry into a cluster and cluster membership maintenance require a sensor node to confirm the presence of features of the object …

Robust Local Search And Its Application To Generating Robust Schedules, Hoong Chuin Lau, Fei Xiao, Thomas Ou

Research Collection School Of Computing and Information Systems

In this paper, we propose an extended local search framework to solve combinatorial optimization problems with data uncertainty. Our approach represents a major departure from scenario-based or stochastic programming approaches often used to tackle uncertainty. Given a value 0 < ? 1, we are interested to know what the robust objective value is, i.e. the optimal value if we allow an chance of not meeting it, assuming that certain data values are defined on bounded random variables. We show how a standard local search or metaheuristic routine can be extended to efficiently construct a decision rule with such guarantee, albeit heuristically. We demonstrate its practical applicability on the Resource Constrained Project Scheduling Problem with minimal and maximal time lags (RCPSP/max) taking into consideration activity duration uncertainty. Experiments show that, partial order schedules can be constructed that are robust in our sense without the need for a large planned horizon (due date), which improves upon the work proposed by Policella et al. 2004.

Evaluating Bag-Of-Visual-Words Representations In Scene Classification, Jun Yang, Yu-Gang Jiang, Alexander G. Hauptmann, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

Based on keypoints extracted as salient image patches, an image can be described as a “bag of visual words” and this representation has been used in scene classification. The choice of dimension, selection, and weighting of visual words in this representation is crucial to the classification performance but has not been thoroughly studied in previous work. Given the analogy between this representation and the bag-of-words representation of text documents, we apply techniques used in text categorization, including term weighting, stop word removal, feature selection, to generate image representations that differ in the dimension, selection, and weighting of visual words. The …

Practical Elimination Of Near-Duplicates From Web Video Search, Xiao Wu, Alexander G. Hauptmann, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

Current web video search results rely exclusively on text keywords or user-supplied tags. A search on typical popular video often returns many duplicate and near-duplicate videos in the top results. This paper outlines ways to cluster and filter out the nearduplicate video using a hierarchical approach. Initial triage is performed using fast signatures derived from color histograms. Only when a video cannot be clearly classified as novel or nearduplicate using global signatures, we apply a more expensive local feature based near-duplicate detection which provides very accurate duplicate analysis through more costly computation. The results of 24 queries in a data …

Role Of Mitochondrial Electron Transport Complex I In Coenzyme Q1 Reduction By Intact Pulmonary Arterial Endothelial Cells And The Effect Of Hyperoxia, Marilyn P. Merker, Said H. Audi, Brian J. Lindemer, Gary S. Krenz, Robert D. Bongard

Biomedical Engineering Faculty Research and Publications

The objective was to determine the impact of intact normoxic and hyperoxia-exposed (95% O(2) for 48 h) bovine pulmonary arterial endothelial cells in culture on the redox status of the coenzyme Q(10) homolog coenzyme Q(1) (CoQ(1)). When CoQ(1) (50 microM) was incubated with the cells for 30 min, its concentration in the medium decreased over time, reaching a lower level for normoxic than hyperoxia-exposed cells. The decreases in CoQ(1) concentration were associated with generation of CoQ(1) hydroquinone (CoQ(1)H(2)), wherein 3.4 times more CoQ(1)H(2) was produced in the normoxic than hyperoxia-exposed cell medium (8.2 +/- 0.3 and 2.4 +/- 0.4 microM, …

Characterization And Modeling Of Low-Frequency Noise In Hf-Based High -Kappa Dielectrics For Future Cmos Applications, Purushothaman Srinivasan

Dissertations

The International Technology Roadmap for Semiconductors outlines the need for high-K dielectric based gate-oxide Metal Oxide Semiconductor Field Effect Transistors for sub-45 nm technology nodes. Gate oxides of hafnium seem to be the nearest and best alternative for silicon dioxide, when material, thermal and structural properties are considered. Usage of poly-Si as a gate electrode material degrades the performance of the device and hence gate stacks based on metal gate electrodes are gaining high interest. Though a substantial improvement in the performance has been achieved with these changes, reliability issues are a cause of concern. For analog and mixed-signal applications, …

Ion Assisted Magnetron Sputtering Of Tantalum Thin Film Deposition And Characterization, Hua Ren

Dissertations

The purpose of this research was to investigate the effects of ion bombardment on the crystallographic phases of tantalum films during their deposition by magnetron sputtering process, and to gain understanding of the mechanism of the ion-solid interactions during the thin film growth. Tantalum (Ta) exists in two distinct crystallographic phases: a stable α-phase with a body centered cubic (bcc) lattice structure and a metastable β-phase with a tetragonal lattice structure. The tough and ductile α-phase Ta is desired in most industrial applications, such as diffusion barrier layers in integrated circuits, metallic corrosion protective layers, and in biomedical devices. The …

Novel Model Of Cerebrospinal Fluid Dynamics Based On Hemodynamically Driven Cyclic Brain Compliance Variation, Bruno A. Mantilla

Dissertations

This study provides a novel explanation for the CerebrQ-Spinal Fluid (CSF) flow pattern observed in phase contrast cine-MRJ studies. CSF dynamics has been traditionally explained as a bulk flow from the site of production to the site of absorption. Studies done with phase contrast cine-MRI show a more complex CSF movement, that is not explainable by the bulk flow paradigm. This study describes a mechanism explaining how the energy delivered by the heart in each cycle is responsible not only for the blood flow, but also for the CSF circulation. This mechanism is based on a cyclic variation of brain …

Automatic Physical Database Design : Recommending Materialized Views, Wugang Xu

Dissertations

This work discusses physical database design while focusing on the problem of selecting materialized views for improving the performance of a database system. We first address the satisfiability and implication problems for mixed arithmetic constraints. The results are used to support the construction of a search space for view selection problems. We proposed an approach for constructing a search space based on identifying maximum commonalities among queries and on rewriting queries using views. These commonalities are used to define candidate views for materialization from which an optimal or near-optimal set can be chosen as a solution to the view selection …

New Approaches To Scaled-Up Carbon Nanotube Synthesis And Nanotube-Based Metal Composites And Sensors, Amit Goyal

Dissertations

The first phase of the work presented in this dissertation is the development of a scaleable process for the cost-effective synthesis of single walled carbon nanotubes (SWNTs) by thermally-induced catalytic chemical vapor deposition (CVD). With the goal of understanding the growth mechanism and optimize the synthesis process, the effect of CVD and catalyst parameters on nanotube formation was investigated in detail. It was found that nucleation and growth of SWNTs occurred within a few seconds of the introduction of the carbon source, carbon monoxide, at temperatures above 675°C over a Co-Mo/MgO catalyst/support system, resulting in the formation of high quality …

Theoretical Framework For Predicting Joint Reaction And Ground Reaction Forces In A Dynamic Pendulum Tree Model Of Human Motion, Peyman Rajai

Theses

Lagrangian dynamics and the method of superfluous coordinates are applied to find ground and joint reaction forces on the human body modeled as a general branched 2-D pendulum tree system with arbitrary segments and arbitrarily distributed point masses. A theoretical framework is established for predicting these constraint forces during human motion and consequently their effects on dynamics, dynamic stability, energy efficiency and the potential of these forces to produce joint injury and/or pain. Applications to human walking are initiated. During idealized phases where there is only single point contact of the stance leg with the ground such as just after …

Route Recovery Schemes For Link And Node Failure And Link Congestion, Ibrahim Takouna

Theses

Link/Node failure occurs frequently causing service disruption in computer networks. Hardware techniques have been developed to protect the network from Link/Node failure. These techniques work in physical layer, therefore their convergence time is very small. On the other hand, many schemes have been proposed to mitigate the failure influence on the network. These schemes work in upper layers such as the network layer. However, hardware solutions faster than other schemes, but they are expensive. Link/Node failure causes all flows which were using the failed link/node are temporarily interrupted till a new path reestablished.

Three recovery algorithms have been proposed that …