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Articles 1 - 30 of 101
Full-Text Articles in Engineering
Incorporating Machine Learning With Satellite Data To Support Critical Infrastructure Measurement And Sustainable Development, Aggrey Muhebwa
Incorporating Machine Learning With Satellite Data To Support Critical Infrastructure Measurement And Sustainable Development, Aggrey Muhebwa
Doctoral Dissertations
Under the umbrella concept of Artificial Intelligence (AI) for good, recent advances in machine learning and large-scale data analysis have opened new opportunities to solve humanity’s most pressing challenges. Improvements in computation complexity and advances in AI (e.g., Vision Transformers) have led to faster and more effective techniques for extracting high-dimensional patterns from large-scale heterogeneous datasets (big data). Further, as satellite data become increasingly available at varying temporal-spatial resolutions, AI tools are helping us to better understand the underlying causes of environmental and socioeconomic changes at an unprecedented scale, ushering in an era of data-driven decision-making to support sustainable and …
Fpga Security Techniques With Applications To Cloud And Multi-Tenant Use Cases, Xiang Li
Fpga Security Techniques With Applications To Cloud And Multi-Tenant Use Cases, Xiang Li
Doctoral Dissertations
Field programmable gate arrays (FPGAs) are integrated circuits that consist of programmable logic that a user can configure and deploy for applications such as hardware emulation and accelerating high performance computing. In recent years, the emergence of FPGAs in the cloud has led to research on multi-tenant FPGAs. In a multi-tenant scenario, the same FPGA fabric is shared among multiple users, or among multiple untrusting IP cores. Multi-tenancy has economic benefits, largely due to improvements in resource utilization, but also brings new security concerns since the tenants could behave maliciously. Although the tenants sharing an FPGA are logically isolated from …
A Ground-Based L-Band Radar System For Monitoring Forest Temporal Dynamics, Xingjian Chen
A Ground-Based L-Band Radar System For Monitoring Forest Temporal Dynamics, Xingjian Chen
Doctoral Dissertations
L-band FMCW radar is implemented for monitoring forest dynamics. It took short-term and long-term measurements with an internal calibration system that guarantees stability and precision. The radar data is compared to in-situ measurement, which infers causal relationships between radar backscatter signal and forest physiology index such as tree dielectric. This paper explains the relationship between radar signals and environmental components such as precipitation based on the measurement. The radar demonstrates some interesting observations, for example, trees' daily activity and freeze-thaw process.
Mobile Intelligent Agents: Interplay Of Communications, Privacy, And Decision Making, Saeede Enayati
Mobile Intelligent Agents: Interplay Of Communications, Privacy, And Decision Making, Saeede Enayati
Doctoral Dissertations
The development of processors and sensor technologies and the advent of artificial intelligence (AI) have led to the growth of more capable and affordable mobile intelligent agents like unmanned aerial vehicles (UAVs) which have numerous applications in areas such as construction, search and rescue operations, oil and gas, agriculture, etc. The use of AI and machine learning (ML) algorithms in UAVs has enabled real-time data-driven decision-making frameworks but poses numerous challenges including high-impact decision-making, security, energy management, communication, and automation, to name a few. In this dissertation, we propose solutions to some of these problems. First, we give our attention …
Refinement And Performance Analysis Of The Stepped Frequency Microwave Radiometer In Extra Tropical Cyclone Conditions, Jezabel Vilardell Sanchez
Refinement And Performance Analysis Of The Stepped Frequency Microwave Radiometer In Extra Tropical Cyclone Conditions, Jezabel Vilardell Sanchez
Doctoral Dissertations
The Stepped Frequency Microwave Radiometer (SFMR) is a key instrument for estimation of ocean surface wind speed and rain rate in tropical and extra-tropical cyclones research. Through the observed brightness temperature (TB) over a range of six C-band frequencies, the SFMR derives these key parameters used by hurricane specialists to issue watches and warnings. The information gathered with this instru- ment is also pivotal for post-storm studies and satellite calibrations. Currently, the SFMR requires an average time of 5-10 seconds of averaging to cycle through the six di↵erent frequency channels, so in regions with strong wind/rain gradients such as the …
Singular Integration By Interpolation For Integral Equations, Ioannis Kyriakou
Singular Integration By Interpolation For Integral Equations, Ioannis Kyriakou
Doctoral Dissertations
Maxwell’s equations and the laws of Electromagnetics (EM) govern a plethora of electrical, optical phenomena with applications on wireless, cellular, communications, medical and computer hardware technologies to name a few. A major contributor to the technological progress in these areas has been due to the development of simulation and design tools that enable engineers and scientists to model, analyze and predict the EM interactions in their systems of interest. At the core of such tools is the field of Computational Electromagnetics (CEM), which studies the solution of Maxwell’s equations with the aid of computers. The advances in these applications technologies, …
Stimulating Electricity Demand To Enhance Sustainable Human Development In Sub-Saharan Africa, June M. Lukuyu
Stimulating Electricity Demand To Enhance Sustainable Human Development In Sub-Saharan Africa, June M. Lukuyu
Doctoral Dissertations
Sub-Saharan Africa continues to aggressively pursue universal electricity access to drive economic development, improved health, literacy, food security, and gender equality. However, increasing electricity supply and household connections is only one important step towards achieving economic transformation. Countries in the region must also strive for increased use of energy services, not only by households but also for income-generating productive uses and community facilities. Unfortunately, unlike the other regions in the world, increasing electricity access rates in sub-Saharan Africa have not been met with complementary growth in electricity consumption density. Therefore, contrary to the energy efficiency zeitgeist in industrialized regions, countries …
Thermal Transport Across 2d/3d Van Der Waals Interfaces, Cameron Foss
Thermal Transport Across 2d/3d Van Der Waals Interfaces, Cameron Foss
Doctoral Dissertations
Designing improved field-effect-transistors (FETs) that are mass-producible and meet the fabrication standards set by legacy silicon CMOS manufacturing is required for pushing the microelectronics industry into further enhanced technological generations. Historically, the downscaling of feature sizes in FETs has enabled improved performance, reduced power consumption, and increased packing density in microelectronics for several decades. However, many are claiming Moore's law no longer applies as the era of silicon CMOS scaling potentially nears its end with designs approaching fundamental atomic-scale limits -- that is, the few- to sub-nanometer range. Ultrathin two-dimensional (2D) materials present a new paradigm of materials science and …
Security Of Hardware Accelerators In Multi-Tenant Fpga Environments, Shayan Moini
Security Of Hardware Accelerators In Multi-Tenant Fpga Environments, Shayan Moini
Doctoral Dissertations
Field-programmable gate arrays (FPGAs) play an important role in the acceleration of computationally expensive algorithms for machine learning, aerospace, and ASIC prototyping. The emergence of FPGAs in the cloud (cloud FPGAs) has accelerated FPGA adoption in various applications due to their low initial cost and the ability to quickly prototype a design. Multi-tenancy, in which multiple users execute circuitry in the same FPGAs simultaneously with logical isolation, reduces cloud FPGA usage cost and increases FPGA utilization. Multi-tenancy introduces new security challenges, such as remote side-channel and fault injection attacks, that cannot be addressed with traditional countermeasures against attacks. In this …
Enabling Daily Tracking Of Individual’S Cognitive State With Eyewear, Soha Rostaminia
Enabling Daily Tracking Of Individual’S Cognitive State With Eyewear, Soha Rostaminia
Doctoral Dissertations
Research studies show that sleep deprivation causes severe fatigue, impairs attention and decision making, and affects our emotional interpretation of events, which makes it a big threat to public safety, and mental and physical well-being. Hence, it would be most desired if we could continuously measure one’s drowsiness and fatigue level, their emotion while making decisions, and assess their sleep quality in order to provide personalized feedback or actionable behavioral suggestions to modulate sleep pattern and alertness levels with the aim of enhancing performance, well-being, and quality of life. While there have been decades of studies on wearable devices, we …
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Frontiers In The Self-Assembly Of Charged Macromolecules, Khatcher O. Margossian
Doctoral Dissertations
The self-assembly of charged macromolecules forms the basis of all life on earth. From the synthesis and replication of nucleic acids, to the association of DNA to chromatin, to the targeting of RNA to various cellular compartments, to the astonishingly consistent folding of proteins, all life depends on the physics of the organization and dynamics of charged polymers. In this dissertation, I address several of the newest challenges in the assembly of these types of materials. First, I describe the exciting new physics of the complexation between polyzwitterions and polyelectrolytes. These materials open new questions and possibilities within the context …
Hyperspectral Unmixing: A Theoretical Aspect And Applications To Crism Data Processing, Yuki Itoh
Hyperspectral Unmixing: A Theoretical Aspect And Applications To Crism Data Processing, Yuki Itoh
Doctoral Dissertations
Hyperspectral imaging has been deployed in earth and planetary remote sensing, and has contributed the development of new methods for monitoring the earth environment and new discoveries in planetary science. It has given scientists and engineers a new way to observe the surface of earth and planetary bodies by measuring the spectroscopic spectrum at a pixel scale. Hyperspectal images require complex processing before practical use. One of the important goals of hyperspectral imaging is to obtain the images of reflectance spectrum. A raw image obtained by hyperspectral remote sensing usually undergoes conversion to a physical quantity representing the intensity of …
Models And Machine Learning Techniques For Improving The Planning And Operation Of Electricity Systems In Developing Regions, Santiago Correa Cardona
Models And Machine Learning Techniques For Improving The Planning And Operation Of Electricity Systems In Developing Regions, Santiago Correa Cardona
Doctoral Dissertations
The enormous innovation in computational intelligence has disrupted the traditional ways we solve the main problems of our society and allowed us to make more data-informed decisions. Energy systems and the ways we deliver electricity are not exceptions to this trend: cheap and pervasive sensing systems and new communication technologies have enabled the collection of large amounts of data that are being used to monitor and predict in real-time the behavior of this infrastructure. Bringing intelligence to the power grid creates many opportunities to integrate new renewable energy sources more efficiently, facilitate grid planning and expansion, improve reliability, optimize electricity …
Improving The Programmability Of Networked Energy Systems, Noman Bashir
Improving The Programmability Of Networked Energy Systems, Noman Bashir
Doctoral Dissertations
Global warming and climate change have underscored the need for designing sustainable energy systems. Sustainable energy systems, e.g., smart grids, green data centers, differ from the traditional systems in significant ways and present unique challenges to system designers and operators. First, intermittent renewable energy resources power these systems, which break the notion of infinite, reliable, and controllable power supply. Second, these systems come in varying sizes, spanning over large geographical regions. The control of these dispersed and diverse systems raises scalability challenges. Third, the performance modeling and fault detection in sustainable energy systems is still an active research area. Finally, …
X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv
X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv
Doctoral Dissertations
Phased-array weather radar have potential to replace reflector dish radar in major weather radar networks such as NEXRAD, providing faster update times and greater scan flexibility. However, the use of electronic scanning introduces polarization errors on weather radar measurables, requiring polarimetric bias calibration. The sources of polarimetric bias have been described theoretically, but experimental verification is still limited. Additionally, no standard method of calibration for polarimetric bias exists for phased-arrays. Therefore, the University of Massachusetts Amherst (UMass) presents a fully operational X-Band phased-array weather radar polarimetric testbed. The testbed evaluates the calibration of a planar dual-polarization X-band phased-array radar through …
Data-Driven Control, Modeling, And Forecasting For Residential Solar Power, Akansha Singh Bansal
Data-Driven Control, Modeling, And Forecasting For Residential Solar Power, Akansha Singh Bansal
Doctoral Dissertations
Distributed solar generation is rising rapidly due to a continuing decline in the cost of solar modules. Most residential solar deployments today are grid-tied, enabling them to draw power from the grid when their local demand exceeds solar generation and feed power into the grid when their local solar generation exceeds demand. The electric grid was not designed to support such decentralized and intermittent energy generation by millions of individual users. This dramatic increase in solar power is placing increasing stress on the grid, which must continue to balance its supply and demand despite the potential for large solar fluctuations. …
Silicon Germanium Bicmos Integrated Circuits For Scalable Cryogenic Sensing Applications, Mohsen Hosseini
Silicon Germanium Bicmos Integrated Circuits For Scalable Cryogenic Sensing Applications, Mohsen Hosseini
Doctoral Dissertations
This dissertation is focused on an investigation of BiCMOS cryogenic low noise amplifiers (LNAs) based on Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for simultaneous low noise and low power design and also taking advantage of CMOS circuitry for adding flexibility to the LNA design. Cryogenic LNAs' scalability challenges are discussed and addressed in the dissertation. To achieve that, first, HBTs of three state-of-the-art technologies are characterized and modeled at cryogenic temperature. It is shown that SiGe HBT provides a promising compromise of noise temperature, power consumption, and bandwidth. Moreover, a scalable on-chip approach is proposed and verified for biasing of …
Tailoring Interfaces And Composition For Stable And Efficient Perovskite Solar Cells, Hamza Javaid
Tailoring Interfaces And Composition For Stable And Efficient Perovskite Solar Cells, Hamza Javaid
Doctoral Dissertations
Metal halide perovskite solar cells (PSCs) have revolutionized the field of thin film photovoltaics. Within a decade, the power conversion efficiencies (PCEs) have increased at a phenomenal rate, rising from 3.8% to more than 25% in single-junction devices, moving them ahead of the current silicon-based technology. The high efficiencies of perovskite solar cells (PSCs) and their other unique properties arise from a combination of organic and inorganic components and electronic-ionic conduction, making them excellent candidates for a plethora of applications. However, PSCs face a significant—and ironic—roadblock to commercialization: these light-harvesting materials degrade under sunlight—the very condition they would need …
Towards Higher Power Factor In Semiconductor Thermoelectrics: Bandstructure Engineering And Potential Barriers, Adithya Kommini
Towards Higher Power Factor In Semiconductor Thermoelectrics: Bandstructure Engineering And Potential Barriers, Adithya Kommini
Doctoral Dissertations
To keep up with the current energy demand and to sustain the growth requires efficient use of existing resources. One of the ways to improve efficiency is by converting waste heat to electricity using thermoelectrics. Thermoelectric devices work on the principle of Seebeck effect, where an applied temperature difference across the material results in a potential difference in the material. The possibility of drastic improvements in the efficiency of thermoelectric (TE) devices using semiconductor nanostructured materials renewed interest in thermoelectrics over the last three decades. Introducing confinement, interfaces, and quantum effects using nanostructures for additional control of charge and phonon …
On Improving Robustness Of Hardware Security Primitives And Resistance To Reverse Engineering Attacks, Vinay C. Patil
On Improving Robustness Of Hardware Security Primitives And Resistance To Reverse Engineering Attacks, Vinay C. Patil
Doctoral Dissertations
The continued growth of information technology (IT) industry and proliferation of interconnected devices has aggravated the problem of ensuring security and necessitated the need for novel, robust solutions. Physically unclonable functions (PUFs) have emerged as promising secure hardware primitives that can utilize the disorder introduced during manufacturing process to generate unique keys. They can be utilized as \textit{lightweight} roots-of-trust for use in authentication and key generation systems. Unlike insecure non-volatile memory (NVM) based key storage systems, PUFs provide an advantage -- no party, including the manufacturer, should be able to replicate the physical disorder and thus, effectively clone the PUF. …
Resource Allocation In Distributed Service Networks, Nitish Kumar Panigrahy
Resource Allocation In Distributed Service Networks, Nitish Kumar Panigrahy
Doctoral Dissertations
The past few years have witnessed significant growth in the use of distributed network analytics involving agile code, data and computational resources. In many such networked systems, for example, Internet of Things (IoT), a large number of smart devices, sensors, processing and storage resources are widely distributed in a geographic region. These devices and resources distributed over a physical space are collectively called a distributed service network. Efficient resource allocation in such high performance service networks remains one of the most critical problems. In this thesis, we model and optimize the allocation of resources in a distributed service network. This …
Metasurface Design And Optimization With Adjoint Method, Mahdad Mansouree
Metasurface Design And Optimization With Adjoint Method, Mahdad Mansouree
Doctoral Dissertations
The invention and advancement of optical devices have tremendously changed our life. Devices such as cameras, displays and optical sensors are now an integral part of our lives. Moreover, with the rapid growth in new markets such as virtual reality (VR), augmented reality (AR), autonomous vehicles and internet of things (IoT) the need for optical devices is expected to grow considerably. Recent advances in nano-fabrication techniques have spurred a new wave of interest in optical metasurfaces. Metasurfaces are arrays of wisely selected nano-scattereres that generate desired transformation on the incident light. Metasurfaces provide a new platform for the development of …
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya
Doctoral Dissertations
The need for alternative energy sources has led to extensive research on optimizing the conversion efficiency of thermoelectric (TE) materials. TE efficiency is governed by figure-of-merit (ZT) and it has been an enormously challenging task to increase ZT > 1 despite decades of research due to the interdependence of material properties. Most doped inorganic semiconductors have a high electrical conductivity and moderate Seebeck coefficient, but ZT is still limited by their high lattice thermal conductivity. One approach to address this problem is to decrease thermal conductivity by means of alloying and nanostructuring, another is to consider materials with an inherently low …
Electro-Thermal Transport In Two-Dimensional Materials And Their Heterostructures, Arnab K. Majee
Electro-Thermal Transport In Two-Dimensional Materials And Their Heterostructures, Arnab K. Majee
Doctoral Dissertations
”Smaller is better” is the mantra that has driven semiconductor industry for the past 50 years. The on-going quest for faster electronic switching, higher transistor density, and better device performance, has been driven by a self-fulfilling prophecy popularly known as Moore’s law, according to which the number of transistors per unit area of a chip doubles itself approximately every two years. A modern smartphone has about 8 billion transistors, which is as large as current earth’s population. Although each transistor dissipates negligible power, but the collective power dissipation from all the transistors in an electronic gadget and inefficient heat removing …
Covert Communications In Continuous-Time Systems, Ke Li
Covert Communications In Continuous-Time Systems, Ke Li
Doctoral Dissertations
This dissertation studies covert wireless communications where a transmitter (Alice) intends to transmit messages to a legitimate receiver (Bob) such that the presence of the message is hidden from an attentive warden (Willie). Here we consider pertinent aspects of covert communications that focus on moving such systems closer to implementation. For example, previous studies use the standard discrete-time communication model when analyzing covert communications, since this is commonly assumed without loss of generality in standard communication theory. However, it is not clear that such a model captures the salient aspects of the continuous-time covert communications problem. A power detector that …
Low-Energy Memristors & High-Nonlinearity Selector For Dense Passive Cross-Bar Arrays, Navnidhi K. Upadhyay
Low-Energy Memristors & High-Nonlinearity Selector For Dense Passive Cross-Bar Arrays, Navnidhi K. Upadhyay
Doctoral Dissertations
Memristor or RRAM (Resistive Random Access Memory) based crossbar array architecture (CBA) is considered a leading contender for the next-generation non-volatile memory (NVM) as well as for future computing paradigms, such as in-memory computing, neuromorphic computing, neural networks, analog computing, reconfigurable computing, etc. Among many other attractive properties, memristors’ simple and dense 3D stackable structure is an essential enabler of these promising applications. However, the simplicity and high density of CBA comes at a price. CBA suffers from the so-called sneak path currents flowing through the unselected cells, which severely affects the read margin, makes CBA more power-hungry, increases the …
Addressing Security Challenges In Embedded Systems And Multi-Tenant Fpgas, Georgios Provelengios
Addressing Security Challenges In Embedded Systems And Multi-Tenant Fpgas, Georgios Provelengios
Doctoral Dissertations
Embedded systems and field-programmable gate arrays (FPGAs) have become crucial parts of the infrastructure that supports our modern technological world. Given the multitude of threats that are present, the need for secure computing systems is undeniably greater than ever. Embedded systems and FPGAs are governed by characteristics that create unique security challenges and vulnerabilities. Despite their array of uses, embedded systems are often built with modest microprocessors that do not support the conventional security solutions used by workstations, such as virus scanners. In the first part of this dissertation, a microprocessor defense mechanism that uses a hardware monitor to protect …
A Generalized Method For Predictive Simulation-Based Lower Limb Prosthesis Design, Mark Price
A Generalized Method For Predictive Simulation-Based Lower Limb Prosthesis Design, Mark Price
Doctoral Dissertations
Lower limb prostheses are designed to replace the functions and form of the missing biological anatomy. These functions are hypothesized to improve user outcome measures which are negatively affected by receiving an amputation – such as metabolic cost of transport, preferred walking speed, and perceived discomfort during walking. However, the effect of these design functions on the targeted outcome measures is highly variable, suggesting that these relationships are not fully understood. Biomechanics simulation and modeling tools are increasingly capable of analyzing the effects of a design on the resulting user gait. In this work, prothesis-aided gait is optimized in simulation …
Enabling Iot Authentication, Privacy And Security Via Blockchain, Md Nazmul Islam
Enabling Iot Authentication, Privacy And Security Via Blockchain, Md Nazmul Islam
Doctoral Dissertations
Although low-power and Internet-connected gadgets and sensors are increasingly integrated into our lives, the optimal design of these systems remains an issue. In particular, authentication, privacy, security, and performance are critical success factors. Furthermore, with emerging research areas such as autonomous cars, advanced manufacturing, smart cities, and building, usage of the Internet of Things (IoT) devices is expected to skyrocket. A single compromised node can be turned into a malicious one that brings down whole systems or causes disasters in safety-critical applications. This dissertation addresses the critical problems of (i) device management, (ii) data management, and (iii) service management in …
Design And Biomechanical Evaluation Of A Clutch-Based Energy Storage And Release Assistive Knee Brace, Ericber Jimenez Francisco
Design And Biomechanical Evaluation Of A Clutch-Based Energy Storage And Release Assistive Knee Brace, Ericber Jimenez Francisco
Doctoral Dissertations
Knee osteoarthritis (OA) is a serious degenerative disease affecting over 240 million people around the world. The most disabling symptoms are joint pain, joint stiffness, and reduction in joint functionality. Medial compartment knee OA is the most common case of unicompartmental knee OA, and pain and progression have been associated with tibiofemoral alignment in early to moderate knee OA patients, mainly due to its association with knee loading as measured by knee adduction moment (KAM) and tibiofemoral contact forces (KCF). Valgization knee braces have been developed to correct the malalignment at the tibiofemoral joint, but they have no direct effect …