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Articles 31 - 60 of 98
Full-Text Articles in Engineering
Modular Approach To Spintronics, Kerem Yunus Camsari
Modular Approach To Spintronics, Kerem Yunus Camsari
Open Access Dissertations
There has been enormous progress in the last two decades, effectively combining spintronics and magnetics into a powerful force that is shaping the field of memory devices. New materials and phenomena continue to be discovered at an impressive rate, providing an ever-increasing set of building blocks that could be exploited in designing transistor-like functional devices of the future. The objective of this thesis is to provide a quantitative foundation for this building block approach, so that new discoveries can be integrated into functional device concepts, quickly analyzed and critically evaluated. Through careful benchmarking against available theory and experiments we establish …
Local Network Coding On Packet Erasure Channels -- From Shannon Capacity To Stability Region, Wei-Cheng Kuo
Local Network Coding On Packet Erasure Channels -- From Shannon Capacity To Stability Region, Wei-Cheng Kuo
Open Access Dissertations
Network Coding (NC) has emerged as a ubiquitous technique of communication networks and has extensive applications in both practical implementations and theoretical developments. While the Avalanche P2P file system from Microsoft, the MORE routing protocol, and the COPE coding architecture from MIT have implemented the idea of NC and exhibited promising performance improvements, a significant part of the success of NC stems from the continuing theoretic development of NC capacity, e.g., the Shannon capacity results for the single-flow multi-cast network and the packet erasure broadcast channel with feedback. However, characterizing the capacity for the practical wireless multi-flow network setting remains …
Large Scale Modeling, Model Reduction And Control Design For A Real-Time Mechatronic System, Qiong Li
Large Scale Modeling, Model Reduction And Control Design For A Real-Time Mechatronic System, Qiong Li
Open Access Dissertations
Mechatronics is the synergistic integration of the techniques from mechanical engineering, electrical engineering and information technology, which influences each other mutually. As a multidisciplinary domain, mechatronics is more than mechanical or electronics, and the mechatronic systems are always composed of a number of subsystems with various controllers. From this point of view, a lot of such systems can be defined as large scale system. The key element of such systems is integration. Modeling of mechatronic system is a very important step in developing control design of such products, so as to simulate and analyze their dynamic responses for control design, …
Computational Optical Imaging: Applications In Synthetic Aperture Imaging, Phase Retrieval, And Digital Holography, Dennis Joseph Lee
Computational Optical Imaging: Applications In Synthetic Aperture Imaging, Phase Retrieval, And Digital Holography, Dennis Joseph Lee
Open Access Dissertations
Computational imaging has become an important field, as a merger of both algorithms and physical experiments. In the realm of microscopy and optical imaging, an important application is the problem of improving resolution, which is bounded by wavelength and numerical aperture according to the classic diffraction limit. We will investigate the resolution enhancement of phase objects such as transparent biological cells. One key challenge is how to measure phase experimentally. Standard interferometric techniques have the drawback of being sensitive to environmental vibrations and temperature fluctuations, and they use a reference arm which requires more space and cost. Non-holographic methods provide …
Semcache: Semantics-Aware Caching For Efficient Gpu Offloading, Nabeel Al-Saber
Semcache: Semantics-Aware Caching For Efficient Gpu Offloading, Nabeel Al-Saber
Open Access Dissertations
Graphical Processing Units (GPUs) offer massive, highly-efficient parallelism, making them an attractive target for computation-intensive applications. However, GPUs have a separate memory space which introduces the complexity of manually handling explicit data movements between GPU and CPU memory spaces. Although GPU kernels/libraries have made it easy to improve application performance by offloading computation to GPUs, unfortunately it is very difficult to manually optimize CPU-GPU communication between multiple kernel invocations to avoid redundant communication when using these kernels with complex applications. ^ In this thesis, we introduce SemCache, a semantics-aware GPU cache that automatically manages CPU-GPU communication in addition to optimizing …
Circular Bessel Field Statistics And The Pursuit Of Far-Subwavelength Resolution, Yulu Chen
Circular Bessel Field Statistics And The Pursuit Of Far-Subwavelength Resolution, Yulu Chen
Open Access Dissertations
The statistical description of wave propagation in random media is important for many applications. While polarized light in systems with weakly interacting scatterers and sufficient overall scatter has zero-mean circular Gaussian statistics, the underlying assumptions break down in the Anderson localization and weakly scattering regimes. Although probability density functions for wave intensity and amplitude exist beyond Gaussian statistics, suitable statistical descriptions for the field with strong and weak random scatter were unknown. The first analytical probability density function for the field that is effective in both the Anderson localization regime and the weakly scattering regime is derived by modeling the …
Control Of Modular Multilevel Converters For Grid Integration Of Full-Scale Wind Energy Conversion Systems, Suman Debnath
Control Of Modular Multilevel Converters For Grid Integration Of Full-Scale Wind Energy Conversion Systems, Suman Debnath
Open Access Dissertations
The growing demand for wind power generation has pushed the capacity of wind turbines towards MW power levels. Higher capacity of the wind turbines necessitates operation of the generators and power electronic conversion systems at higher voltage/power levels. The power electronic conversion system of a wind energy conversion system (WECS) needs to meet the stringent requirements in terms of reliability, efficiency, scalability and ease of maintenance, power quality, and dv/dt stress on the generator/transformer. Although the multilevel converters including the neutral point clamped (NPC) converter and the active NPC converter meet most of the requirements, they fall short in reliability …
Fully Electronic Method Of Measuring Post-Release Gap And Gradient/Residual Stress Of A Mems Cantilever, Andrew Stephen Kovacs
Fully Electronic Method Of Measuring Post-Release Gap And Gradient/Residual Stress Of A Mems Cantilever, Andrew Stephen Kovacs
Open Access Dissertations
Smartphones and other wireless devices have become ubiquitous over the past decade, and the RF front-end inside of them has become more complex and disproportionately consumes more power compared to other components. Micro-electromechanical systems (MEMS) have a huge potential to reduce these problems while simultaneously offering superior performance compared to current leading-edge technology. However, MEMS technology has difficulty transitioning from the lab to large-scale manufacturing due to the unpredictability of device lifetime and manufacturability issues. This can be mitigated by investigating how critical material or physical parameters (gap, stress, Young's modulus, material thickness, etc.) vary from manufacturing uncertainties and how …
Dependability Where The Mobile World Meets The Enterprise World, Amiya K. Maji
Dependability Where The Mobile World Meets The Enterprise World, Amiya K. Maji
Open Access Dissertations
As we move toward increasingly larger scales of computing, complexity of systems and networks has increased manifold leading to massive failures of cloud providers (Amazon Cloudfront, November 2014) and geographically localized outages of cellular services (T-Mobile, June 2014). In this dissertation, we investigate the dependability aspects of two of the most prevalent computing platforms today, namely, smartphones and cloud computing. These two seemingly disparate platforms are part of a cohesive story—they interact to provide end-to-end services which are increasingly being delivered over mobile platforms, examples being iCloud, Google Drive and their smartphone counterparts iPhone and Android. ^ In one of …
In Pursuit Of High Resolution Radar Using Pursuit Algorithms, Abdur Rahman Maud
In Pursuit Of High Resolution Radar Using Pursuit Algorithms, Abdur Rahman Maud
Open Access Dissertations
Radar receivers typically employ matched filters designed to maximize signal to noise ratio (SNR) in a single target environment. In a multi-target environment, however, matched filter estimates of target environment often consist of spurious targets because of radar signal sidelobes. As a result, matched filters are not suitable for use in high resolution radars operating in multi-target environments. Assuming a point target model, we show that the radar problem can be formulated as a linear under-determined system with a sparse solution. This suggests that radar can be considered as a sparse signal recovery problem. However, it is shown that the …
Laser Scanner Jitter Characterization, Page Content Analysis For Optimal Rendering, And Understanding Image Graininess, Yi-Ting Chen
Laser Scanner Jitter Characterization, Page Content Analysis For Optimal Rendering, And Understanding Image Graininess, Yi-Ting Chen
Open Access Dissertations
In Chapter 1, the electrophotographic (EP) process is widely used in imaging systems such as laser printers and office copiers. In the EP process, laser scanner jitter is a common artifact that mainly appears along the scan direction due to the condition of polygon facets. Prior studies have not focused on the periodic characteristic of laser scanner jitter in terms of the modeling and analysis. This chapter addresses the periodic characteristic of laser scanner jitter in the mathematical model. In the Fourier domain, we derive an analytic expression for laser scanner jitter in general, and extend the expression assuming a …
Advanced Wireless Communications Using Large Numbers Of Transmit Antennas And Receive Nodes, Junil Choi
Advanced Wireless Communications Using Large Numbers Of Transmit Antennas And Receive Nodes, Junil Choi
Open Access Dissertations
The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD massive MIMO be used for training signal transmissions and channel state information (CSI) feedback. First, we propose …
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Open Access Dissertations
The exponential miniaturization of Si CMOS technology has been a key to the electronics revolution. However, the continuous downscaling of the gate length becomes the biggest challenge to maintain higher speed, lower power, and better electrostatic integrity for each following generation. Hence, novel devices and better channel materials than Si are considered to improve the metal-oxide-semiconductor field-effect transistors (MOSFETs) device performance. III-V compound semiconductors and multi-gate structures are being considered as promising candidates in the next CMOS technology. III-V and Si nano-scale transistors in different architectures are investigated (1) to compare the performance between InGaAs of III-V compound semiconductors and …
Power-Efficient High-Speed Interface Circuit Techniques, Elkim Felipe Roa Fuentes
Power-Efficient High-Speed Interface Circuit Techniques, Elkim Felipe Roa Fuentes
Open Access Dissertations
Inter- and intra-chip connections have become the new challenge to enable the scaling of computing systems, ranging from mobile devices to high-end servers. Demand for aggregate I/O bandwidth has been driven by applications including high-speed ethernet, backplane micro-servers, memory, graphics, chip-to-chip and network onchip. I/O circuitry is becoming the major power consumer in SoC processors and memories as the increasing bandwidth demands larger per-pin data rate or larger I/O pin count per component. The aggregate I/O bandwidth has approximately doubled every three to four years across a diverse range of standards in different applications. However, in order to keep pace …
Computing With Spintronics: Circuits And Architectures, Rangharajan Venkatesan
Computing With Spintronics: Circuits And Architectures, Rangharajan Venkatesan
Open Access Dissertations
This thesis makes the following contributions towards the design of computing platforms with spintronic devices. 1) It explores the use of spintronic memories in the design of a domain-specific processor for an emerging class of data-intensive applications, namely recognition, mining and synthesis (RMS). Two different spintronic memory technologies — Domain Wall Memory (DWM) and STT-MRAM — are utilized to realize the different levels in the memory hierarchy of the domain-specific processor, based on their respective access characteristics. Architectural tradeoffs created by the use of spintronic memories are analyzed. The proposed design achieves 1.5X-4X improvements in energy-delay product compared to a …
Estimating Toner Usage With Laser Electrophotographic Printers, And Object Map Generation From Raster Input Image, Lu Wang
Open Access Dissertations
Accurate estimation of toner usage is an area of on-going importance for laser, electrophotographic (EP) printers. In Part 1, we propose a new two-stage approach in which we first predict on a pixel-by-pixel basis, the absorptance from printed and scanned pages. We then form a weighted sum of these pixel values to predict overall toner usage on the printed page. The weights are chosen by least-squares regression to toner usage measured with a set of printed test pages. Our two-stage predictor significantly outperforms existing methods that are based on a simple pixel counting strategy in terms of both accuracy and …
Image Analysis Using Visual Saliency With Applications In Hazmat Sign Detection And Recognition, Bin Zhao
Image Analysis Using Visual Saliency With Applications In Hazmat Sign Detection And Recognition, Bin Zhao
Open Access Dissertations
Visual saliency is the perceptual process that makes attractive objects "stand out" from their surroundings in the low-level human visual system. Visual saliency has been modeled as a preprocessing step of the human visual system for selecting the important visual information from a scene. We investigate bottom-up visual saliency using spectral analysis approaches. We present separate and composite model families that generalize existing frequency domain visual saliency models. We propose several frequency domain visual saliency models to generate saliency maps using new spectrum processing methods and an entropy-based saliency map selection approach. A group of saliency map candidates are then …
Tunable Impedance Matching Network Fundamental Limits And Pracitical Considerations, Wesley N. Allen
Tunable Impedance Matching Network Fundamental Limits And Pracitical Considerations, Wesley N. Allen
Open Access Dissertations
As wireless devices continue to increase in utility while decreasing in dimension, design of the RF front-end becomes more complex. It is common for a single handheld device to operate on a plethora of frequency bands, utilize multiple antennae, and be subjected to a variety of environments. One complexity in particular which arises from these factors is that of impedance mismatch. Recently, tunable impedance matching networks have begun to be implemented to address this problem. ^ This dissertation presents the first in-depth study on the frequency tuning range of tunable impedance matching networks. Both the fundamental limitations of ideal networks …
Dynamic Control Of Plasmonic Resonances With Graphene Based Nanostructures, Naresh Kumar Emani
Dynamic Control Of Plasmonic Resonances With Graphene Based Nanostructures, Naresh Kumar Emani
Open Access Dissertations
Light incident on a metallic structure excites collective oscillations of electrons termed as plasmons. These plasmons are useful in control and manipulation of information in nanoscale dimensions and at high operating frequencies. Hence, the field of plasmonics opens up the possibility of developing nanoscale optoelectronic circuitry for computing and sensing applications. One of the challenges in this effort is the lack of tunable plasmonic resonance. Currently, the resonant wavelength of plasmonic structure is fixed by the material and structural parameters. Post-fabrication dynamic control of a plasmonic resonance is rather limited.^ In this thesis we explore the combination of optoelectrical properties …
Application Of Integer Quadratic Programming In Detection Of High-Dimensional Wireless Systems, Ali Ahmed Elghariani
Application Of Integer Quadratic Programming In Detection Of High-Dimensional Wireless Systems, Ali Ahmed Elghariani
Open Access Dissertations
High-dimensional wireless systems have recently generated a great deal of interest due to their ability to accommodate increasing demands for high transmission data rates with high communication reliability. Examples of such large-scale systems include single-input, single-output symbol spread OFDM system, large-scale single-user multi-input multi-output (MIMO) OFDM systems, and large-scale multiuser MIMO systems. In these systems, the number of symbols required to be jointly detected at the receiver is relatively large. The challenge with the practical realization of these systems is to design a detection scheme that provides high communication reliability with reasonable computational complexity, even as the number of simultaneously …
Quantifying Aesthetics Of Visual Design Applied To Automatic Design, Ali Jahanian
Quantifying Aesthetics Of Visual Design Applied To Automatic Design, Ali Jahanian
Open Access Dissertations
In today's "Instagram" world, with advances in ubiquitous computing and access to social networks, digital media is adopted by art and culture. In this dissertation, we study what makes a good design by investigating mechanisms to bring aesthetics of design from realm of subjection to objection. These mechanisms are a combination of three main approaches: learning theories and principles of design by collaborating with professional designers, mathematically and statistically modeling good designs from large scale datasets, and crowdscourcing to model perceived aesthetics of designs from general public responses. We then apply the knowledge gained in automatic design creation tools to …
Material And Device Aspects Of Semiconducting Two-Dimensional Crystals, Han Liu
Material And Device Aspects Of Semiconducting Two-Dimensional Crystals, Han Liu
Open Access Dissertations
Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D …
Nearly Orthogonal, Doppler Tolerant Waveforms And Signal Processing For Multi-Mode Radar Applications, Uttam Kumar Majumder
Nearly Orthogonal, Doppler Tolerant Waveforms And Signal Processing For Multi-Mode Radar Applications, Uttam Kumar Majumder
Open Access Dissertations
In this research, we investigate the design and analysis of nearly orthogonal, Doppler tolerant waveforms for diversity waveform radar applications. We then present a signal processing framework for joint synthetic aperture radar (SAR) and ground moving target indication (GMTI) processing that is built upon our proposed waveforms. ^ To design nearly orthogonal and Doppler tolerant waveforms, we applied direct sequence spread spectrum (DSSS) coding techniques to linear frequency modulated (LFM) signals. The resulting transmitted waveforms are rendered orthogonal using a unique spread spectrum code. At the receiver, the echo signal can be decoded using its spreading code. In this manner, …
Application Of Integer Quadratic Programming To Detection Of High-Dimensional Wireless Systems, Jamal Yousuf Alsawalhi
Application Of Integer Quadratic Programming To Detection Of High-Dimensional Wireless Systems, Jamal Yousuf Alsawalhi
Open Access Dissertations
This work introduces a novel permanent-magnet synchronous machine (PMSM) architecture that employs rotational asymmetry to increase the torque density output in constant power variable speed applications. A population based multi-objective design optimization algorithm is used to design and analyze the new machine topology. A number of design studies are presented to show that the proposed machine structure outperforms a conventional PMSM machine. Validation of the analytical machine design model using a three dimensional finite element analyses is performed and the results are presented. Finally, a case study in which a hybrid electric bus traction motor is designed is presented.
Analysis And Practical Considerations In Implementing Multiple Transmitters And Receivers For Wireless Power Transfer Via Coupled Magnetic Resonance, Rizal Johari
Open Access Dissertations
The technology to wirelessly power mobile devices has started to gain momentum especially in industry. Cables have started to become the thing of the past as both wireless power efficiency and communication speeds become viably attractive. The first part of this work gives analysis and practical considerations in implementing multiple transmitters for wireless power transfer via coupled magnetic resonance. Through the multiple transmitter scheme, there is an increase in gain and `diversity' of the transmitted power according to the number of transmit coils. The effect of transmitter resonant coil coupling is also shown. Resonant frequency detuning due to nearby metallic …
Algorithm-Circuit Co-Design For Detecting Symptomatic Patterns In Biological Signals, Himanshu Markandeya
Algorithm-Circuit Co-Design For Detecting Symptomatic Patterns In Biological Signals, Himanshu Markandeya
Open Access Dissertations
The advancement in scaled Silicon technology has accelerated the development of a wide range of applications in various fields including medical technology. It has immensely contributed to finding solutions for monitoring general health as well as alleviating intractable disorders in the form of implantable and wearable systems. This necessitates the development of energy efficient and functionally efficacious systems. This thesis has explored the algorithm-circuit co-design approach for developing an energy efficient epileptic seizure detection processor which could be used for implantable epilepsy prosthesis. Novel wavelet transform based algorithms are proposed for accurate detection of epileptic seizures. Energy efficient techniques at …
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Open Access Dissertations
An important pursuit in semiconductor physics is to discover new materials to sustain the continuous progress and improvements in the current electronic devices. Traditionally, three material types are in use: 1) Metals 2) Semiconductors 3) Insulators. All the three material types are classified according to the energy gap between conduction and valence bands derived from band theory of solids. Recent theoretical predictions and confirmed by experimental observations have provided evidence that there exists materials which behave as insulators in the bulk but possess gapless conducting states on the surface. These new class of materials are called topological insulators (TI). In …
Design And Analysis Of Solar Cells By Coupled Electrical - Optical Simulation, Xufeng Wang
Design And Analysis Of Solar Cells By Coupled Electrical - Optical Simulation, Xufeng Wang
Open Access Dissertations
Careful electrical design and optical design are both crucial for achieving high-efficiency solar cells. It is common to link these two aspects serially; the optical design is first done to minimize reflection and maximize light trapping, and then the resulting optical generation rate is input to the electrical simulation. For very high efficiency solar cells that approach the Shockley-Queisser limit, however, electrical and optical transports are tightly coupled in both directions. Photons generated by radiative recombination can be reabsorbed to create additional electron-hole pairs (so-called photon recycling), which decreases losses. A variety of novel photon management schemes are currently being …
Modeling And Characterization Of Non-Ideal Effects In High-Performance Rf Mems Tuners, Juan Zeng
Modeling And Characterization Of Non-Ideal Effects In High-Performance Rf Mems Tuners, Juan Zeng
Open Access Dissertations
The emerging standards for the next-generation wireless communication system demand for multi-band RF front-ends. Reconfigurable RF devices based on MEMS technology have emerged with the potential to significantly reduce the system complexity and cost. Robust operation of RF MEMS tuners under the non-ideal effects due to fabrication uncertainties and environmental variations is critical in achieving reliable RF MEMS reconfigurable devices. Therefore, it is essential to model and characterize these non-ideal effects, and further to alleviate these non-ideal effects by design optimization.^ In this dissertation, the effects of non-perfect anchor support, residual stress, and temperature sensibility of MEMS tuners have been …
Microwave Chemical Sensing Using Overmoded T-Line Designs And Impact Of Real-Time Digitizer In The System, Yu-Ting Huang
Microwave Chemical Sensing Using Overmoded T-Line Designs And Impact Of Real-Time Digitizer In The System, Yu-Ting Huang
Open Access Dissertations
Microwave spectrometers have unique advantages in the ability to determine high resolution features that are specific to a given chemical. Very sharp lines which correspond to quantum states of the chemical allow for unique identification of the chemical. Recent advances have shown the possibility of room temperature microwave spectroscopy analysis in which the data is collected in a short amount of time using broadband chirp pulse Fourier transform microwave (CP-FTMW) spectroscopy. In this report, we explore the design of reduced size spectrometers focusing on the reduction as well as expansion of operation frequency of the microwave analysis cell, where the …