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Articles 91 - 120 of 121
Full-Text Articles in Engineering
Scalable Autonomous Operations Of Unmanned Assets, Sunghun Jung
Scalable Autonomous Operations Of Unmanned Assets, Sunghun Jung
Open Access Dissertations
Although there have been great theoretical advances in the region of Unmanned Aerial Vehicle (UAV) autonomy, applications of those theories into real world are still hesitated due to unexpected disturbances. Most of UAVs which are currently used are mainly, strictly speaking, Remotely Piloted Vehicles (RPA) since most works related with the flight control, sensor data analysis, and decision makings are done by human operators. To increase the degree of autonomy, many researches are focused on developing Unmanned Autonomous Aerial Vehicle (UAAV) which can takeoff, fly to the interested area by avoiding unexpected obstacles, perform various missions with decision makings, come …
Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz
Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz
Open Access Dissertations
The noninvasive measurement of finite displacements and strains in biomaterials by magnetic resonance imaging (MRI) may be shown to enable mathematical estimates of stress distributions and material properties within structures of the body such as articular cartilage or the intervertebral disc. Such methods will allow for non-contact and patient-specific modeling in a manner not currently possible with traditional mechanical testing or finite element techniques. Therefore, the objective of this thesis was to develop computational methods incorporating imaging-based measures of deformation, composition, and local microstructure to permit nondestructive analysis of a range of complex biomechanical systems.
Finite strain-based models were developed …
Rf To Millimeter-Wave Linear Power Amplifiers In Nanoscale Cmos Soi Technology, Jing-Hwa Chen
Rf To Millimeter-Wave Linear Power Amplifiers In Nanoscale Cmos Soi Technology, Jing-Hwa Chen
Open Access Dissertations
The low manufacturing cost, integration capability with baseband and digital circuits, and high operating frequency of nanoscale CMOS technologies have propelled their applications into RF and microwave systems. Implementing fully-integrated RF to millimeter-wave (mm-wave) CMOS power amplifiers (PAs), nevertheless, remains challenging due to the low breakdown voltages of CMOS transistors and the loss from on-chip matching networks. These limitations have reduced the design space of CMOS power amplifiers to narrow-band, low linearity metrics often with insufficient gain, output power, and efficiency.
A new topology for implementing power amplifiers based on stacking of CMOS SOI transistors is proposed. The input RF …
A Novel Multistage Image Registration Technique With Graph-Based Region Descriptors, Francis Ryals Bowen
A Novel Multistage Image Registration Technique With Graph-Based Region Descriptors, Francis Ryals Bowen
Open Access Dissertations
Successful image alignment is an essential function for many image processing methods. The geometric and photometric variations between images adversely affect the ability for an algorithm to estimate the transformation parameters that relate the two images. Local deformations, lightning conditions, object obstructions, and perspective differences all contribute to the challenges faced by traditional registration techniques. In this work, a novel multistage registration approach is proposed that is resilient to view point differences, image content variations, and lighting conditions. The proposed method is demonstrated to be effective for registration scenarios involving images of a scene or object before and after a …
Non-Silicon Mosfets And Circuits With Atomic Layer Deposited Higher-K Dielectrics, Lin Dong
Non-Silicon Mosfets And Circuits With Atomic Layer Deposited Higher-K Dielectrics, Lin Dong
Open Access Dissertations
The quest for technologies beyond 14nm node complementary metal-oxide-semiconductor (CMOS) devices has now called for research on higher-k gate dielectrics integration with high mobility channel materials such as III-V semiconductors and germanium. Ternary oxides, such as La2-xYxO3 and LaAlO3, have been considered as strong candidates due to their high dielectric constants and good thermal stability. Meanwhile, the unique abilities of delivering large area uniform thin film, excellent controlling of composition and thickness to an atomic level, which are keys to ultra-scaled devices, have made atomic layer deposition (ALD) technique an excellent choice.
In this thesis, we systematically study the atomic …
Technology Agnostic Analysis And Design For Improved Performance, Variability, And Reliability In Thin Film Photovoltaics, Sourabh Dongaonkar
Technology Agnostic Analysis And Design For Improved Performance, Variability, And Reliability In Thin Film Photovoltaics, Sourabh Dongaonkar
Open Access Dissertations
Thin film photovoltaics (TFPV) offer low cost alternatives to conventional crystalline Silicon (c-Si) PV, and can enable novel applications of PV technology. Their large scale adoption however, requires significant improvements in process yield, and operational reliability. In order to address these challenges, comprehensive understanding of factors affecting panel yield, and predictive models of performance reliability are needed. This has proved to be especially challenging for TFPV for two reasons in particular. First, TFPV technologies encompass a wide variety of materials, processes, and structures, which fragments the research effort. Moreover, the monolithic manufacturing of TFPV modules differs significantly from that of …
Techniques To Increase Computational Efficiency In Some Deterministic And Random Electromagnetic Propagation Problems, Selman Ozbayat
Techniques To Increase Computational Efficiency In Some Deterministic And Random Electromagnetic Propagation Problems, Selman Ozbayat
Open Access Dissertations
Efficient computation in deterministic and uncertain electromagnetic propagation environments, tackled by parabolic equation methods, is the subject of interest of this dissertation. Our work is comprised of two parts. In the first part we determine efficient absorbing boundary conditions for propagation over deterministic terrain and in the second part we study techniques for efficient quantification of random parameters/outputs in volume and surface based electromagnetic problems.
Domain truncation by transparent boundary conditions for open problems where parabolic equation is utilized to govern wave propagation are in general computationally costly. For the deterministic problem, we utilize two approximations to a convolution-in-space type …
Reconfigurable Technologies For Next Generation Internet And Cluster Computing, Deepak C. Unnikrishnan
Reconfigurable Technologies For Next Generation Internet And Cluster Computing, Deepak C. Unnikrishnan
Open Access Dissertations
Modern web applications are marked by distinct networking and computing characteristics. As applications evolve, they continue to operate over a large monolithic framework of networking and computing equipment built from general-purpose microprocessors and Application Specific Integrated Circuits (ASICs) that offers few architectural choices. This dissertation presents techniques to diversify the next-generation Internet infrastructure by integrating Field-programmable Gate Arrays (FPGAs), a class of reconfigurable integrated circuits, with general-purpose microprocessor-based techniques. Specifically, our solutions are demonstrated in the context of two applications - network virtualization and distributed cluster computing.
Network virtualization enables the physical network infrastructure to be shared among several …
Hybrid Radio Frequency And Video Framework For Identity-Aware Augmented Perception In Disaster Management And Assistive Technologies, Xunyi Yu
Open Access Dissertations
In this dissertation, we introduce a hybrid radio frequency and video framework that enables identity aware-augmented perception. Identity-aware augmented perception enhances users' perception of the surrounding by collecting and analyzing information pertaining to each identifiable or tractable target nearby aggregated from various sensors, and presents it visually or audibly augmenting users' own sensory perceptions. We target two application areas of disaster management and assistive technologies. Incident commanders and first responders can use the technology to perceive information specific to a victim, e.g. triage level, critical conditions, visually superimposed on third person or first person video. The blind and visually impaired …
Online Management Of Resilient And Power Efficient Multicore Processors, Rance Rodrigues
Online Management Of Resilient And Power Efficient Multicore Processors, Rance Rodrigues
Open Access Dissertations
The semiconductor industry has been driven by Moore's law for almost half a century. Miniaturization of device size has allowed more transistors to be packed into a smaller area while the improved transistor performance has resulted in a significant increase in frequency. Increased density of devices and rising frequency led, unfortunately, to a power density problem which became an obstacle to further integration. The processor industry responded to this problem by lowering processor frequency and integrating multiple processor cores on a die, choosing to focus on Thread Level Parallelism (TLP) for performance instead of traditional Instruction Level Parallelism (ILP).
While …
Vehicular Ad Hoc Networks: Interplay Of Geometry, Communications, And Traffic, Mohammad Nekoui
Vehicular Ad Hoc Networks: Interplay Of Geometry, Communications, And Traffic, Mohammad Nekoui
Open Access Dissertations
Vehicular Ad Hoc Networks (VANETs) have been proposed to enhance the safety and efficiency of transportation systems. Such networks hold unique characteristics and fulfill new goals that necessitate their study from a whole new perspective other than what has been the prevailing paradigm for conventional Mobile Ad Hoc Networks (MANETs). The mission of this dissertation is to identify such unique characteristics and propose design strategies for VANETs that target the new system goals.
We argue that the road and obstacle geometry are two important factors that should be appropriately addressed when studying the communications throughput of VANETs. To this end …
Nasics: A `Fabric-Centric' Approach Towards Integrated Nanosystems, Pritish Narayanan
Nasics: A `Fabric-Centric' Approach Towards Integrated Nanosystems, Pritish Narayanan
Open Access Dissertations
This dissertation addresses the fundamental problem of how to build computing systems for the nanoscale. With CMOS reaching fundamental limits, emerging nanomaterials such as semiconductor nanowires, carbon nanotubes, graphene etc. have been proposed as promising alternatives. However, nanoelectronics research has largely focused on a `device-first' mindset without adequately addressing system-level capabilities, challenges for integration and scalable assembly.
In this dissertation, we propose to develop an integrated nano-fabric, (broadly defined as nanostructures/devices in conjunction with paradigms for assembly, inter-connection and circuit styles), as opposed to approaches that focus on MOSFET replacement devices as the ultimate goal. In the `fabric-centric' mindset, design …
Information Measures For Statistical Orbit Determination, Alinda Kenyana Mashiku
Information Measures For Statistical Orbit Determination, Alinda Kenyana Mashiku
Open Access Dissertations
The current Situational Space Awareness (SSA) is faced with a huge task of tracking the increasing number of space objects. The tracking of space objects requires frequent and accurate monitoring for orbit maintenance and collision avoidance using methods for statistical orbit determination. Statistical orbit determination enables us to obtain estimates of the state and the statistical information of its region of uncertainty given by the probability density function (PDF). As even collision events with very low probability are important, accurate prediction of collisions require the representation of the full PDF of the random orbit state. Through representing the full PDF …
Orientation Controllable Epitaxial Vapor-Liquid-Solid Semiconductor Nanowire Synthesis On Silicon Substrate, Sung Hwan Chung
Orientation Controllable Epitaxial Vapor-Liquid-Solid Semiconductor Nanowire Synthesis On Silicon Substrate, Sung Hwan Chung
Open Access Dissertations
Semiconductor nanowires synthesized via the vapor-liquid-solid (VLS) mechanism have attracted extensive research interest in recent years owing to their unique structure as a promising candidate for the future electronic devices. Germanium and silicon nanowires, in particular, are compatible with the current silicon-based technology via direct assembly. However, one of the main challenges for the successful nanowire application in large-scale is the lack of the method for obtaining nanowires in desired positions and directions. Therefore, the comprehensive, systematic understanding of epitaxial nanowire growth and the more suitable method to align nanowires on novel structure are required. In this work, the synthesis …
Robust And Scalable Domain Decomposition Methods For Electromagnetic Computations, Georgios Paraschos
Robust And Scalable Domain Decomposition Methods For Electromagnetic Computations, Georgios Paraschos
Open Access Dissertations
The Finite Element Tearing and Interconnecting (FETI) and its variants are probably the most celebrated domain decomposition algorithms for partial differential equation (PDE) scientific computations. In electromagnetics, such methods have advanced research frontiers by enabling the full-wave analysis and design of finite phased array antennas, metamaterials, and other multiscale structures. Recently, closer scrutiny of these methods have revealed robustness and numerical scalability problems that prevent the most memory and time efficient variants of FETI from gaining widespread acceptance. This work introduces a new class of FETI methods and preconditioners that lead to exponential iterative convergence for a wide class of …
Security Issues In Network Virtualization For The Future Internet, Sriram Natarajan
Security Issues In Network Virtualization For The Future Internet, Sriram Natarajan
Open Access Dissertations
Network virtualization promises to play a dominant role in shaping the future Internet by overcoming the Internet ossification problem. Since a single protocol stack cannot accommodate the requirements of diverse application scenarios and network paradigms, it is evident that multiple networks should co-exist on the same network infrastructure. Network virtualization supports this feature by hosting multiple, diverse protocol suites on a shared network infrastructure. Each hosted virtual network instance can dynamically instantiate custom set of protocols and functionalities on the allocated resources (e.g., link bandwidth, CPU, memory) from the network substrate. As this technology matures, it is important to consider …
Security Issues In Networked Embedded Devices, Danai Chasaki Sr
Security Issues In Networked Embedded Devices, Danai Chasaki Sr
Open Access Dissertations
Embedded devices are ubiquitous; they are present in various sectors of everyday life: smart homes, automobiles, health care, telephony, industrial automation, networking etc. Embedded systems are well known for their dependability, and that is one of the reasons that they are preferred over general purpose machines in various applications. Traditional embedded computing is changing nowadays mainly due to the increasing number of heterogeneous embedded devices that are, more often than not, interconnected. Security in the field of networked embedded systems is becoming particularly important, because:
1) Connected embedded devices can be attacked remotely.
2) They are resource constrained.
This means, …
Accuracy Of Biomass And Structure Estimates From Radar And Lidar, Razi Uddin Ahmed
Accuracy Of Biomass And Structure Estimates From Radar And Lidar, Razi Uddin Ahmed
Open Access Dissertations
A better understanding of ecosystem processes requires accurate estimates of forest biomass and structure on global scales. Recently, there have been demonstrations of the ability of remote sensing instruments, such as radar and lidar, for the estimation of forest parameters from spaceborne platforms in a consistent manner. These advances can be exploited for global forest biomass accounting and structure characterization, leading to a better understanding of the global carbon cycle. The popular techniques for estimation of forest parameters from radar instruments in particular, use backscatter intensity, interferometry and polarimetric interferometry. This dissertation analyzes the accuracy of biomass and structure estimates …
Power Efficient Continuous-Time Delta-Sigma Modulator Architectures For Wideband Analog To Digital Conversion, Mohammad Ranjbar
Power Efficient Continuous-Time Delta-Sigma Modulator Architectures For Wideband Analog To Digital Conversion, Mohammad Ranjbar
Open Access Dissertations
This work presents novel continuous-time delta-sigma modulator architectures with low-power consumption and improved signal transfer functions which are suitable for wideband A/D conversion in wireless applications, e.g., 3G and 4G receivers. The research has explored two routes for improving the overall performance of continuous-time delta-sigma modulator. The first part of this work proposes the use of the power efficient Successive-Approximations (SAR) architecture, instead of the conventional Flash ADC, as the internal quantizer of the delta-sigma modulator. The SAR intrinsic latency has been addressed by means of a faster clock for the quantizer as well as full-period delay compensation. The use …
Queue Length Based Pacing Of Internet Traffic, Cai Yan
Queue Length Based Pacing Of Internet Traffic, Cai Yan
Open Access Dissertations
As the Internet evolves, there is a continued demand for high Internet bandwidth. This demand is driven partly by the widely spreading real-time video applications, such as on-line gaming, teleconference, high-definition video streaming. All-optical switches and routers have long been studied as a promising solution to the rapidly growing demand. Nevertheless, buffer sizes in all-optical switches and routers are very limited due to the challenges in manufacturing larger optical buffers. On the other hand, Internet traffic is bursty. The existence of burstiness in network traffic has been shown at all time scales, from tens of milliseconds to thousands of seconds. …
Clock Generation And Distribution For Enhancing Immunity To Power Supply Noise, Jinwook Jang
Clock Generation And Distribution For Enhancing Immunity To Power Supply Noise, Jinwook Jang
Open Access Dissertations
Clock generation and distribution are getting difficult due to increased die size and increased number of cores in a microprocessor. Clock frequencies of microprocessors have been increased and expected to trend 4GHz in near future. This increased clock frequency requires to limit the clock skew and jitter to 5~10% of clock frequency, which is 12.5~25ps. On top of this, non-ideal power supply behavior (supply droops) is worsening available timing margin to the critical paths. This dissertation presents three types of interrelated works: 1) analytical modeling of period jitter of global clock distribution induced by power supply droop, 2) circuit design …
Low-Profile, Modular, Ultra-Wideband Phased Arrays, Steven S. Holland
Low-Profile, Modular, Ultra-Wideband Phased Arrays, Steven S. Holland
Open Access Dissertations
Ultrawideband (UWB) phased antenna arrays are critical to the success of future multi-functional communication, sensing, and countermeasure systems, which will utilize a few UWB phased arrays in place of multiple antennas on a platform. The success of this new systems approach relies in part on the ability to manufacture and assemble low-cost UWB phased arrays with excellent radiation characteristics.This dissertation presents the theory and design of a new class of UWB arrays that is based on unbalanced fed tightly-coupled horizontal dipoles over a ground plane. Practical implementation of this concept leads to two inexpensive wideband array topologies, the Banyan Tree …
Informativeness And The Computational Metrology Of Collaborative Adaptive Sensor Systems, Anthony P. Hopf
Informativeness And The Computational Metrology Of Collaborative Adaptive Sensor Systems, Anthony P. Hopf
Open Access Dissertations
Complex engineered systems evolve, with a tendency toward self-organization, which can, paradoxically, frustrate the aims of those seeking to develop them. The systems engineer, seeking to promote the development in the context of changing and uncertain requirements, is challenged by conceptual gaps that emerge within engineering projects, particularly as they scale up, that inhibit communication among the various stakeholders. Overall optimization, involving multiple criterion, is often expressed in the language of the individual parties, increasing the complexity of the overall situation, subsuming the participants within the evolution of the complex engineered system, containing the objective and subjective in counterproductive or …
Band Structure Calculations Of Strained Semiconductors Using Empirical Pseudopotential Theory, Jiseok Kim
Band Structure Calculations Of Strained Semiconductors Using Empirical Pseudopotential Theory, Jiseok Kim
Open Access Dissertations
Electronic band structure of various crystal orientations of relaxed and strained bulk, 1D and 2D confined semiconductors are investigated using nonlocal empirical pseudopotential method with spin-orbit interaction. For the bulk semiconductors, local and nonlocal pseudopotential parameters are obtained by fitting transport-relevant quantities, such as band gap, effective masses and deformation potentials, to available experimental data. A cubic-spline interpolation is used to extend local form factors to arbitrary q and the resulting transferable local pseudopotential V(q) with correct work function is used to investigate the 1D and 2D confined systems with supercell method. Quantum confinement, uniaxial and biaxial strain and crystal …
Low Cost Electronically Steered Phase Arrays For Weather Applications, Mauricio Sanchez-Barbetty
Low Cost Electronically Steered Phase Arrays For Weather Applications, Mauricio Sanchez-Barbetty
Open Access Dissertations
The Electronically Steered Phased Array is one of the most versatile antennas used in radars applications. Some of the advantages of electronic steering are faster scan, no moving parts and higher reliability. However, the cost of phased arrays has always been prohibitive - in the order of $1M per square meter. The cost of a phased array is largely impacted by the cost of the high frequency electronics at each element and the cost of packaging. Advances in IC integration will allow incorporating multiple elements such as low noise amplifier, power amplifier, phase shifters and up/down-conversion into one or two …
Managing Lithographic Variations In Design, Reliability, And Test Using Statistical Techniques, Aswin Sreedhar
Managing Lithographic Variations In Design, Reliability, And Test Using Statistical Techniques, Aswin Sreedhar
Open Access Dissertations
Much of today's high performance computing engines and hand-held mobile devices are products of aggressive CMOS scaling. Technology scaling in semiconductor industry is mainly driven by corresponding improvements in optical lithography technology. Photolithography, the art used to create patterns on the wafer is at the heart of the semiconductor manufacturing process. Lately, improvements in optical technology have been difficult and slow. The transition to deep ultra-violet (DUV) light source (193nm) required changes in lens materials, mask blanks, light source and photoresist. It took more than ten years to develop a stable chemically amplified resist (CAR) for DUV. Consequently, as the …
Hole Mobility In Strained Ge And Iii-V P-Channel Inversion Layers With Self-Consistent Valence Subband Structure And High-K Insulators, Yan Zhang
Open Access Dissertations
We present a comprehensive investigation of the low-¯eld hole mobility in strained Ge and III-V (GaAs, GaSb, InSb and In1¡xGaxAs) p-channel inversion layers with both SiO2 and high-· insulators. The valence (sub)band structure of Ge and III-V channels, relaxed and under strain (tensile and compressive) is calculated using an effcient self-consistent method based on the six-band k ¢ p perturbation theory. The hole mobility is then computed using the Kubo-Greenwood formalism accounting for non-polar hole-phonon scattering (acoustic and optical), surface roughness scatter- ing, polar phonon scattering (III-Vs only), alloy scattering (alloys only) and remote phonon scattering, accounting for multi-subband dielectric …
On Detection, Analysis And Characterization Of Transient And Parametric Failures In Nano-Scale Cmos Vlsi, Alodeep Sanyal
On Detection, Analysis And Characterization Of Transient And Parametric Failures In Nano-Scale Cmos Vlsi, Alodeep Sanyal
Open Access Dissertations
As we move deep into nanometer regime of CMOS VLSI (45nm node and below), the device noise margin gets sharply eroded because of continuous lowering of device threshold voltage together with ever increasing rate of signal transitions driven by the consistent demand for higher performance. Sharp erosion of device noise margin vastly increases the likelihood of intermittent failures (also known as parametric failures) during device operation as opposed to permanent failures caused by physical defects introduced during manufacturing process. The major sources of intermittent failures are capacitive crosstalk between neighbor interconnects, abnormal drop in power supply voltage (also known as …
Diversifying The Internet, Yong Liao
Diversifying The Internet, Yong Liao
Open Access Dissertations
Diversity is a widely existing and much desired property in many networking systems. This dissertation studies diversity problems in Internet, which is the largest computer networking system in the world. The motivations of diversifying the Internet are two-fold. First, diversifying the Internet improves the Internet routing robustness and reliability. Most problems we have encountered in our daily use of Internet, such as service interruptions and service quality degradation, are rooted in the inter-domain routing system of Internet. Inter-domain routing is policy-based routing, where policies are often based on commercial agreements between ASes. Although people know how to safely accommodate a …
A Hardware/Software Co-Design Architecture For Thermal, Power, And Reliability Management In Chip Multiprocessors, Omer Khan
Open Access Dissertations
Today’s designs are being shaped by the challenges of nano-CMOS technologies: increased power density, rising junction temperatures, and rising rate of errors and device failures that constrain average rate of power dissipation, and design technologies that limit peak power delivery. This thesis focuses on how to leverage the hardware and software abstraction layers of today’s systems. Several of the low level hardware details such as power, hotspots, and faults are tightly correlated to interactions within the system including application and hardware behavior. The conventional approach to tackling such problems come with additional costs and design complexity, and they are limited …