Electrical and Computer Engineering Commons^™

Linear Precoding For Mimo Multiple Access Channels With Discrete-Constellation Inputs, Mingxi Wang, Weiliang Zeng, Chengshan Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we study linear precoding for multiple-input multiple-output (MIMO) multiple access channels (MAC) with discrete-constellation inputs. We derive the constellation-constrained capacity region for the MIMO MAC with an arbitrary number of users. Due to the non-concavity of the objective function, we obtain the necessary conditions for the weighted sum rate (WSR) maximization problem through Karush-Kuhn-Tucker (KKT) analysis. to find the optimal precoding matrices, we propose an iterative algorithm utilizing alternating optimization strategy and gradient descent update. Numerical results show that when inputs are digital modulated signals and the signal-to-noise ratio (SNR) is in the medium range, our proposed …

Mahalanobis-Taguchi System As A Multi-Sensor Based Decision Making Prognostics Tool For Centrifugal Pump Failures, Ahmet Soylemezoglu, Sarangapani Jagannathan, Can Saygin

Electrical and Computer Engineering Faculty Research & Creative Works

A novel Mahalanobis Taguchi System (MTS) based fault detection, isolation, and prognostics scheme is presented. the proposed scheme fuses data from multiple sensors into a single system level performance metric using Mahalanobis Distance (MD) and generates fault clusters based on MD values. MD thresholds derived from the clustering analysis are used for fault detection and isolation. When a fault is detected, the prognostics scheme, which monitors the progression of the MD values over time, is initiated. Then, using a linear approximation, time to failure is estimated. the performance of the scheme has been validated via experiments performed on a mono-block …

On The Preconditioner Of Conjugate Gradient Method A Power Grid Simulation Perspective, Chung Han Chou, Nien Yu Tsai, Hao Yu, Che Rung Lee, Yiyu Shi, Shih Chieh Chang

Electrical and Computer Engineering Faculty Research & Creative Works

Preconditioned Conjugate Gradient (PCG) method has been demonstrated to be effective in solving large-scale linear systems for sparse and symmetric positive definite matrices. One critical problem in PCG is to design a good preconditioner, which can significantly reduce the runtime while keeping memory usage efficient. Universal preconditioners are simple and easy to construct, but their effectiveness is highly problem dependent. on the other hand, domain-specific preconditioners that explore the underlying physical meaning of the matrices usually work better but are difficult to design. in this paper, we study the problem in the context of power grid simulation, and develop a …

Decomposition Of Reversible Logic Function Based On Cube-Reordering, Martin Lukac, Michitaka Kameyama, Marek Perkowski, Pawel Kerntopf

Electrical and Computer Engineering Faculty Publications and Presentations

We present a novel approach to the synthesis of incompletely specified reversible logic functions. The method is based on cube grouping; the first step of the synthesis method analyzes the logic function and generates groupings of same cubes in such a manner that multiple sub-functions are realized by a single Toffoli gate. This process also reorders the function in such a manner that not only groups of similarly defined cubes are joined together but also don’t care cubes. The proposed method is verified on standard benchmarks for both reversible and irreversible logic functions. The obtained results show that for functions …

Mixed Integral-Differential Skin-Effect Models For Peec Electromagnetic Solver, Giulio Antonini, Albert E. Ruehli, Lijun Jiang

Electrical and Computer Engineering Faculty Research & Creative Works

Efficient modeling of the broadband skin-effect for conducting 3D shapes is a challenging issue for the solution of large electromagnetic problems. The inclusion of such models in an EM solver can be very costly in compute time and memory requirements. Several properties of a model are desirable for the solution of practical problems such as the broadband frequency domain or the time domain applicability. In this paper, we present a model which meets some of these challenges and which is suitable for the PEEC solution method. © 2011 IEEE.

Modeling And Characterization Of P-Type Silicon Carbide Gate Turn Off Thyristors, Osama Shihadeh Saadeh

Graduate Theses and Dissertations

Silicon carbide (SiC) power semiconductor devices have emerged in the past decade as the most promising technology for next generation power electronic applications ranging for electric vehicles to grid-connected power routing and conversion interfaces. Several devices have been developed, and even some have been released commercially, including diodes, MOSFETs, JFETs, thyristors, gate turn-off thyristors, and IGBTs. The model development, characterization and experimental validation of SiC p-type Gate Turn-off Thyristors (GTO) is presented in this work. The GTO device in this work is being used as part of a SiC-based solid-state fault current limiter under development at the University of Arkansas' …

Investigation Of A Floating Load Buck Dc-Dc Switching Converter, Hong Tan

Graduate Theses and Dissertations

A floating load buck DC-DC switching converter was analyzed, simulated, designed and prototyped. The floating load buck converter is first compared to the conventional buck converter. It was found that both the floating load buck converter and conventional buck converter exhibit similar conversion characteristics despite the differences in the placement of their output inductors. A floating load buck converter was designed to be used as a high-voltage off-line light-emitting diodes (LEDs) driver using a Texas Instruments' TPS92001 controller. Finally, the characteristics of this floating load buck converter LED driver were experimentally examined.

Design Of A Low Noise Amplifier For Wireless Sensor Networks, Ting Liu

Graduate Theses and Dissertations

CMOS technology becomes important in Radio Frequency (RF) communication systems which include both a receiver and a transmitter. In a high performance radio receiver, the Low Noise Amplifier (LNA) is the first circuit, and its noise performance dominates the entire receiver. Depending upon the system in which they are used, LNAs can be designed according to various topologies and structures. The LNA needs to have matched input impedance, and at the same time it should amplify the small amplitude input signal without adding too much noise and still have the minimal power consumption. It also needs a good interface with …

Fabrication Of Composite Nanomaterials For Thin Film Amorphous Silicon Solar Cells, Benjamin Seth Newton

Graduate Theses and Dissertations

A material with the precise combination of amorphous silicon and polycrystalline silicon would be able to take advantage of the high absorption capabilities of amorphous silicon and the electron transport capabilities of polycrystalline silicon. Polycrystalline nanostructures in the form of wires can also take advantage of other properties of light absorption, trapping and scattering inherent in nanowire structures. These properties of high absorption and electron transport in one device would lead to advances in the search for highly efficient low cost solar cells and sensors. In this work a thin film material composed of an array of polycrystalline silicon nanostructures …

Detection-Assisted Object Tracking By Mobile Cameras, Li He

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Tracking-by-detection is a class of new tracking approaches that utilizes recent development of object detection algorithms. This type of approach performs object detection for each frame and uses data association algorithms to associate new observations to existing targets. Inspired by the core idea of the tracking-by-detection framework, we propose a new framework called detection-assisted tracking where object detection algorithm provides help to the tracking algorithm when such help is necessary; thus object detection, a very time consuming task, is performed only when needed. The proposed framework is also able to handle complicated scenarios where cameras are allowed to move, and …

Optical And Magnetic Properties Of Feni Slanted Columnar Thin Films Infiltrated With Pmma And Fe3O4 Nanoparticles, Dan Liang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, dielectric polymer and magnetic nanoparticles were utilized to hybridize FeNi Slanted columnar thin films (SCTFs). Firstly Fe₃O₄ in PMMA matrix was prepared by physical blending process. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to investigate the dispersion of the nanoparticles in PMMA matrix and the preparation conditions were varied to optimize the dispersion. The hybridized materials were prepared by the infiltration of PMMA and 5 wt% Fe₃O₄ nanoparticles/PMMA to the voids of FeNi SCTFs. Spin-coating and annealing process were employed to reach an excellent infiltration.

The structural …

A 2-D Processor Array For Massively Parallel Image Processing, Anantha Krishna Nelliparthi

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

The concept of introducing image processing logic within the spatial gaps of an array of photodiodes is the key factor behind the presented work. A two-dimensional massively parallel image processing paradigm based on 8X8 pixel neighborhood digital processors has been designed. A low complexity processor array architecture along with its instruction set has been designed and fully verified on a FPGA platform. Various image processing tests have been run on the FPGA platform to demonstrate the functionality of a design that uses 12 parallel processors. The test results indicate that the architecture is scalable to support high frame rates while …

Optimized Built-In Self-Test Technique For Caen-Based Nanofabric Systems, Sambhav Kundaikar, Maciej Zawodniok

Electrical and Computer Engineering Faculty Research & Creative Works

We propose a built-in self-test (BIST) technique for testing and diagnosis of molecular electronic based nano fabrics. the nano fabric architectures are reconfigurable in nature thus making it possible to utilize general methods similar to those employed for testing of FPGAs. However, a high defect rate in nano fabrics renders the traditional techniques ill-suited. Moreover, the nano blocks offer potential for using a partially damaged nano block due to inherent redundancy of the architecture. This paper presents the design and analysis of testing configurations and optimization scheme that minimizes testing time while improving the utilization of the nano fabric. the …

On The Linear Precoder Design For Mimo Channels With Finite-Alphabet Inputs And Statistical Csi, Weiliang Zeng, Chengshan Xiao, Mingxi Wang, Jianhua Lu

Electrical and Computer Engineering Faculty Research & Creative Works

This paper investigates the linear precoder design that maximizes the average mutual information of multiple-input multiple-output channels with finite-alphabet inputs and statistical channel state information known at the transmitter. This linear precoder design is an important open problem and is extremely difficult to solve: First, average mutual information lacks closed-form expression and involves complicated computations; Second, the optimization problem over precoder is nonconcave. This study explores the solution to this problem and provides the following contributions: 1) a closed-form lower bound of average mutual information is derived. It achieves asymptotic optimality at low and high signal-to-noise ratio regions and, with …

Validation Of The Triply Selective Fading Channel Model Through A Mimo Test Bed And Experimental Results, Saurav Subedi, Huang Lou, Fei Ren, Mingxi Wang, Y. Rosa Zheng

Electrical and Computer Engineering Faculty Research & Creative Works

Multiple-input multiple-output (MIMO) channel is often triply selective, meaning that it has spatial, temporal and inter-tap correlation. the temporal correlation is well characterized by its Doppler spectrum, but spatial and inter-tap correlation and their impact on MIMO channels are less studied in the literature. a MIMO testbed has been established to measure the impulse response of MIMO channels and an estimation method is developed to quantitatively measure the correlation matrices from experimental data. © 2011 IEEE.

Sensing And Transmission Strategies In Wireless Cognitive Radio Systems, Babak Abbasi Bastami

UNLV Theses, Dissertations, Professional Papers, and Capstones

The main challenge in any cognitive radio system is to maximize secondary users throughput while limiting interference imposed on licensed users. In this regard, finding the optimal sensing and transmission timing strategies and accurate sensing techniques are of great importance in a cognitive radio network.

In this thesis, we study a sensing-transmission scheme for secondary user in a cognitive radio system where the secondary user senses every primary channel independently and transmits a signal for a fixed duration if it finds the channel empty and stays idle for another fixed duration if it senses the channel busy. We obtain optimal …

Development Of A Simulation Tool For Analysis Of Freeway Crashes Due To Cell Phone Usage, Sourabh Sriom

UNLV Theses, Dissertations, Professional Papers, and Capstones

Research shows that drivers are susceptible to numerous distractions while driving which can be held responsible as the reason of a crash. Usage of cell phones, i.e. talking or texting while driving is considered one of the prominent distractions which causes a crash. This dissertation aims to study the number of crashes occurring on the freeways and their relation with the drivers of these cars using cell phones while they are driving. Since crashes occur relatively less frequently, the study of crashes is done using what is called the "rare event" theory. Java based simulations are done to model a …

Distributed Electrical Power System In Cubesat Applications, Robert Burt

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The cubesat spacecraft was conceived over ten years ago. Since that time, close to 100 cubesat satellites have either been launched or are in the process of construction. Although started as an educational teaching tool, the cubesat is gaining popularity in the satellite industry and is making inroads as a standard architecture for many nano and pico satellite applications. The electrical power system for the cubesat class satellites almost exclusively conforms to a centralized architecture.

This thesis researches the potential of using a distributed architecture for the cubesat power system. There are several key advantages of a distributed architecture that …

Prediction Models For Estimation Of Soil Moisture Content, Swathi Gorthi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Center for Self-Organizing Intelligent Systems (CSOIS) has been successful in developing personal remote sensing systems. These systems can be further enhanced to monitor important resources of earth such as soil moisture content. Soil moisture is the major component of the soil in relation to plant growth. Soil water dissolves salts and makes up the soil solution, which is important as medium for supply of nutrients to growing plants.

Usually, measuring such physical quantities would include using derived formulas that mathematically describe the relationships between the parameters involved. With the advancements in computer modeling, other methods such as empirical modeling …

Subthreshold 3 Phase Mixers, Jesus Angel Torres

Theses and Dissertations - UTB/UTPA

This thesis will discuss subthreshold FET mixers with a focus on conversion loss derivations. To begin understanding the mixers, a look into the FET model is first taken in Chapter II. Then in Chapter III, a single FET device mixer is studied and its conversion loss is found from its small-signal model. The chapter will then include a two FET device mixer and a four device FET mixer. Finally a new type of mixer will be discussed in Chapter IV. The new type of mixer is a 3 phase mixer with the phase angles being 0°, 120°, and 240°. The …