Engineering Commons^™

Performance Analysis Of Cognitive Radio Systems Under Qos Constraints And Channel Uncertainty, Sami Akin, Mustafa Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, performance of cognitive transmission over time-selective flat fading channels is studied under quality of service (QoS) constraints and channel uncertainty. Cognitive secondary users (SUs) are assumed to initially perform channel sensing to detect the activities of the primary users, and then attempt to estimate the channel fading coefficients through training. Energy detection is employed for channel sensing, and different minimum mean-square-error (MMSE) estimation methods are considered for channel estimation. In both channel sensing and estimation, erroneous decisions can be made, and hence, channel uncertainty is not completely eliminated. In this setting, performance is studied and interactions between …

Mimo Wireless Communications Under Statistical Queueing Constraints, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

The performance of multiple-input multiple-output (MIMO) wireless systems is investigated in the presence of statistical queueing constraints. Queuing constraints are imposed as limitations on buffer violation probabilities. The performance under such constraints is captured through the effective capacity formulation. A detailed analysis of the effective capacity is carried out in the low-power, wideband, and high signal-to-noise ratio (SNR) regimes. In the low-power analysis, expressions for the first and second derivatives of the effective capacity with respect to SNR at SNR = 0 are obtained under various assumptions on the degree of channel state information at the transmitter. Transmission strategies that …

Secure Wireless Communication And Optimal Power Control Under Statistical Queueing Constraints, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, secure transmission of information over fading broadcast channels is studied in the presence of statistical queueing constraints. Effective capacity is employed as a performance metric to identify the secure throughput of the system, i.e., effective secure throughput. It is assumed that perfect channel side information (CSI) is available at both the transmitter and the receivers. Initially, the scenario in which the transmitter sends common messages to two receivers and confidential messages to one receiver is considered. For this case, the effective secure throughput region, which is the region of constant arrival rates of common and …

Enhancement Of Optical Emission From Laser-Induced Plasmas By Combined Spatial And Magnetic Confinement, L. B. Guo, W. Hu, B. Y. Zhang, X. N. He, C. M. Li, Y. S. Zhou, Z. X. Cai, X. Y. Zeng, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Within the past decades, laser-induced breakdown spectroscopy (LIBS) has become a well-established and powerful optical emission spectroscopy (OES) analytical technique [1–5]. As a useful analytical tool, LIBS is used extensively in various areas such as remote detection, hostile environment monitoring, and cultural heritage conservation [6–10]. Researchers are paying more attention to LIBS as a diagnostic method for elemental analysis as it is characterized by fast, real-time, in situ, low invasiveness, and multi-elemental diagnosis, normally without the need for sample preparation [11,12]. However, one of its major drawbacks is its low sensitivity, which seriously hinders further improving the limit of detection …

Apparatus For Dispensing Material, Peter Werner Sutter, Eli Anguelova Sutter

Department of Electrical and Computer Engineering: Faculty Publications

An apparatus capable of dispensing drops of material with volumes on the order of Zeptoliters is described. In some embodiments of the inventive pipette the size of the droplets so dispensed is determined by the size of a hole, or channel, through a carbon shell encapsulating a reservoir that contains material to be dispensed. The channel may be formed by irradiation with an electronbeam or other high-energy beam capable of focusing to a spot size less than about 5 nanom eters. In some embodiments, the dispensed droplet remains attached to the pipette by a small thread of material, an atomic …

Generation Of High-Temperature And Low-Density Plasmas For Improved Spectral Resolutions In Laser-Induced Breakdown Spectroscopy, X. N. He, W. Hu, C. M. Li, L. B. Guo, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Improved spectral resolutions were achieved in laser-induced breakdown spectroscopy (LIBS) through generation of high-temperature and low-density plasmas. A first pulse from a KrF excimer laser was used to produce particles by perpendicularly irradiating targets in air. A second pulse from a 532 nm Nd:YAG laser was introduced parallel to the sample surface to reablate the particles. Optical scattering from the first-pulse plasmas was imaged to elucidate particle formation in the plasmas. Narrower line widths (full width at half maximums: FWHMs) and weaker self-absorption were observed from time-integrated LIBS spectra. Estimation of plasma temperatures and densities indicates that high temperature and …

Support Vector Machine-Based Short-Term Wind Power Forecasting, Jianwu Zeng, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

This paper proposes a support vector machine (SVM)-based statistical model for wind power forecasting (WPF). Instead of predicting wind power directly, the proposed model first predicts the wind speed, which is then used to predict the wind power by using the power-wind speed characteristics of the wind turbine generators. Simulation studies are carried out to validate the proposed model for very short-term and short-term WPF by using the data obtained from the National Renewable Energy Laboratory (NREL). Results show that the proposed model is accurate for very short-term and short-term WPF and outperforms the persistence model as well as the …

High Power Current Sensorless Bidirectional 16-Phase Interleaved Dc-Dc Converter For Hybrid Vehicle Application, Liqin Ni, Dean J. Patterson, Jerry L. Hudgins

Department of Electrical and Computer Engineering: Faculty Publications

A new 16-phase interleaved bidirectional dc/dc converter is developed featuring smaller input/output filters, faster dynamic response and lower device stress than conventional designs, for hybrid vehicle applications. The converter is connected between the ultracapacitor (UC) pack and the battery pack in a multisource energy storage system of a hybrid vehicle. Typically, multiphase interleaved converters require a current control loop in each phase to avoid imbalanced current between phases. This increases system cost and control complexity. In this paper, in order to minimize imbalance currents and remove the current control loop in each phase, the converter is designed to operate in …

Iterative Construction Of Regular Ldpc Codes From Independent Tree-Based Minimum Distance Bounds, Eric T. Psota, Lance C. Perez

Department of Electrical and Computer Engineering: Faculty Publications

An independent tree-based method for lower bounding the minimum distance of low-density parity-check (LDPC) codes is presented. This lower-bound is then used as the decision criterion during the iterative construction of regular LDPC codes. The new construction algorithm results in LDPC codes with greater girth and improved minimum-distance bounds when compared to regular LDPC codes constructed using the progressive edge-growth (PEG) construction and the approximate cycle extrinsic message degree (ACE)-constrained PEG construction. Simulation results of codes constructed with the new method show improved performance on the additive white Gaussian noise channel at moderate signal-to-noise ratios.

Constant Power Control Of Dfig Wind Turbines With Supercapacitor Energy Storage, Liyan Qu, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

With the increasing penetration of wind power into electric power grids, energy storage devices will be required to dynamically match the intermittency of wind energy. This paper proposes a novel two-layer constant power control scheme for a wind farm equipped with doubly fed induction generator (DFIG) wind turbines. Each DFIG wind turbine is equipped with a super-capacitor energy storage system (ESS) and is controlled by the low-layer wind turbine generator (WTG) controllers and coordinated by a high-layer wind farm supervisory controller (WFSC). The WFSC generates the active power references for the low-layer WTG controllers according to the active power demand …

Nano-Particle/Quantum Dot Based Optical Dode, Dennis R. Alexander, John C. Bruce, Craig A. Zuhlke, Brandon E. Koch, Jitender S. Deogun, Haitham S. Hamza

Department of Electrical and Computer Engineering: Faculty Publications

A particle based optical diode having at least two cavities or at least two regions of a single cavity, wherein the regions contain different types of particles.

Performance Analysis Of Mimo-Sess With Alamouti Scheme Over Rayleigh Fading Channels, Shichuan Ma, Lim Nguyen, Yaoqing Lamar Yang, Won Mee Jang

Department of Electrical and Computer Engineering: Faculty Publications

Self-encoded spread spectrum (SESS) is a novel modulation technique that acquires its spreading sequence from the random input data stream rather than through the use of the traditional pseudo-noise code generator. It has been incorporated with multiple-input multiple-output (MIMO) systems as a means to combat fading in wireless channels. In this paper, we present the analytical study of the bit-error rate (BER) performance of MIMO-SESS systems under Rayleigh fading. The BER expressions are derived in closed form, and the veracity of the analysis is confirmed by numerical calculations that demonstrate excellent agreement with simulation results. The performance analysis shows that …

All-Dielectric Invisibility Cloaks Made Of Batio3-Loaded Polyurethane Foam, Di Bao, Khalid Z. Rajab, Yang Hao, Efthymios Kallos, Wenxuan Tang, Christos Argyropoulos, Yongzhe Piao, Shoufeng Yang

Department of Electrical and Computer Engineering: Faculty Publications

Transformation optics has led the way in the development of electromagnetic invisibility cloaks from science fiction to engineering practice. Invisibility cloaks have been demonstrated over a wide range of the electromagnetic spectrum, and with a variety of different fabrication techniques. However, all previous schemes have relied on the use of metamaterials consisting of arrays of sub-wavelength inclusions. We report on the first cloaking structure made of a high-k dielectric-loaded foam mixture. A polyurethane foam mixed with different ratios of barium titanate is used to produce the required range of permittivities, and the invisibility cloak is demonstrated to work for all …

Reprogrammed Transcriptome In Rhesus-Bovine Interspecies Somatic Cell Nuclear Transfer Embryos, Kai Wang, Hasan H. Otu, Ying Chen, Young Lee, Keith Latham, Jose B. Cibelli

Department of Electrical and Computer Engineering: Faculty Publications

Background: Global activation of the embryonic genome (EGA), one of the most critical steps in early mammalian embryo development, is recognized as the time when interspecies somatic cell nuclear transfer (iSCNT) embryos fail to thrive.

Methodology/Principal Findings: In this study, we analyzed the EGA-related transcriptome of rhesus-bovine iSCNT 8- to 16- cell embryos and dissected the reprogramming process in terms of embryonic gene activation, somatic gene silencing, and maternal RNA degradation. Compared with fibroblast donor cells, two thousand and seven genes were activated in iSCNT embryos, one quarter of them reaching expression levels comparable to those found in in vitro …

A High-Quality Mach-Zehnder Interferometer Fiber Sensor By Femtosecond Laser One-Step Processing, Longjiang Zhao, Lan Jiang, Sumei Wang, Hai Xiao, Yongfeng Lu, Hai-Lung Tsai

Department of Electrical and Computer Engineering: Faculty Publications

During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is …

On The Performance Limits Of Cognitive Mimo Channels, Sami Akin, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, throughput of cognitive multiple-input multiple-output (MIMO) systems operating under quality-of service (QoS) constraints is studied. It is assumed that transmission power and the covariance of the input signal vector are varied depending on the sensed activities of primary users in the system. Considering the reliability of the transmission and channel sensing results, a state-transition model is provided. Effective capacity is determined, and expressions for the first and second derivatives of the effective capacity are obtained at SNR = 0. The minimum bit energy requirements in the presence of QoS limitations are identified. Numerical results are provided.

Energy-Efficient Feedback Tracking On Embedded Smart Cameras By Hardware-Level Optimization, Mauricio Casares, Senem Velipasalar, Paolo Santinelli, Rita Cucchiara, Reggio Emilia, Andrea Prati

Department of Electrical and Computer Engineering: Faculty Publications

Embedded systems have limited processing power, memory and energy. When camera sensors are added to an embedded system, the problem of limited resources becomes even more pronounced. In this paper, we introduce two methodologies to increase the energy-efficiency and battery-life of an embedded smart camera by hardware-level operations when performing object detection and tracking. The CITRIC platform is employed as our embedded smart camera. First, down-sampling is performed at hardware level on the micro-controller of the image sensor rather than performing software-level down-sampling at the main microprocessor of the camera board. In addition, instead of performing object detection and tracking …

Energy Efficiency And Goodput Analysis In Two-Way Wireless Relay Networks, Qing Chen, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, we study two-way relay networks (TWRNs) in which two source nodes exchange their information via a relay node indirectly in Rayleigh fading channels. Both Amplify-and-Forward (AF) and Decode-and-Forward (DF) techniques have been analyzed in the TWRN employing a Markov chain model through which the network operation is described and investigated in depth. Automatic Repeat-reQuest (ARQ) retransmission has been applied to guarantee the successful packet delivery. The bit energy consumption and goodput expressions have been derived as functions of transmission rate in a given AF or DF TWRN. Numerical results are used to identify the optimal transmission rates …

Goodput Maximization In Cooperative Networks With Arq, Qing Chen, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, the average successful throughput, i.e., goodput, of a coded 3-node cooperative network is studied in a Rayleigh fading environment. It is assumed that a simple automatic repeat request (ARQ) technique is employed in the network so that erroneously received packets are retransmitted until successful delivery. The relay is assumed to operate in either amplify-and-forward (AF) or decode-and-forward (DF) mode. Under these assumptions, retransmission mechanisms and protocols are described, and the average time required to send information successfully is determined. Subsequently, the goodput for both AF and DF relaying is formulated. The tradeoffs and interactions between the …

Ann-Based Adaptive Pi Control For Wind Turbine With Doubly Fed Induction Generator, Baohua Dong, Sohrab Asgarpoor, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

This paper focuses on developing a novel algorithm which dynamically optimizes the controllers of doubly fed induction generator (DFIG) driven by a wind turbine (WT) to increase DFIG transient performance in all wind speed conditions. Particle swarm optimization (PSO) is proposed to optimize parameters of PI controllers of DFIG’s rotor side/grid side converters (RSC/GSC) at different wind speeds in order to maximize the damping ratios of the system eigenvalues in small signal stability analysis. Based on the optimal values and the wind speed data set, an artificial neural network (ANN) is designed, trained, and it has the ability to quickly …

Throughput Analysis Of Buffer-Constrained Wireless Systems In The Finite Blocklength Regime, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, wireless systems operating under queueing constraints in the form of limitations on the buffer violation probabilities are considered. The throughput of wireless systems operating under such constraints is captured by the effective capacity formulation. It is assumed that finite blocklength codes are employed for transmission. Under this assumption, a recent result on the channel coding rate in the finite blocklength regime is incorporated into the analysis and the throughput achieved with such codes in the presence of queueing constraints is identified. Interactions between the effective rate, queueing constraints, error probabilities, and blocklength values are investigated. In particular, …

Series-Connected Self-Reconfigurable Multicell Battery, Taesic Kim, Wei Qiao, Liyan Qu

Department of Electrical and Computer Engineering: Faculty Publications

This paper proposes a novel series-connected, self-reconfigurable, multi-cell battery design. A new cell switching circuit topology is proposed and implemented by using high efficiency semiconductor devices for dynamic configuration of the multi-cell battery. Each cell in the battery only uses two switches to fully control its operation independently. The proposed design can maximally utilize the battery’s capacity and is tolerant to failures of single or multiple cells. These prolong the operating time and lifespan and enhance the reliability of the battery system. By using the proposed design, additional monitoring, control, protection and optimization functions can be readily added to each …

Risk-Based Failure Mode And Effect Analysis For Wind Turbines (Rb-Fmea), Salman Kahrobaee, Sohrab Asgarpoor

Department of Electrical and Computer Engineering: Faculty Publications

Failure Mode and Effect Analysis (FMEA) has already been used as a qualitative measure for identifying failure modes and causes, in order to mitigate the effects of failure in different sectors of power systems. This paper presents a quantitative approach called Risk-Based-FMEA, based on the failure probabilities and incurred failure costs instead of rating scales. As a case study, this approach has been applied to a direct drive wind turbine. The results show that the definition of failure modes priorities based on their contribution to the total failure cost of the wind turbine is more realistic and practical than the …

Self-Reconfigurable Multicell Batteries, Taesic Kim, Wei Qiao, Liyan Qu

Department of Electrical and Computer Engineering: Faculty Publications

The traditional multicell battery design usually employs a fixed configuration to connect multiple cells in series and parallel during operation in order to achieve the required voltage and current. However, this fixed configuration results in low reliability, low fault tolerance, and non-optimal energy conversion efficiency. This paper proposes a novel self reconfigurable, multicell battery design. The proposed multicell battery can automatically configure itself according to the dynamic load/storage demand and the condition of each cell. The proposed battery can self-heal from failure or abnormal operation of single or multiple cells, self-balance from cell state variations, and self-optimize to achieve the …

A Dual-Network Testbed For Wireless Sensor Applications, Jedrzej Kowalczuk, Mehmet C. Vuran, Lance C. Pérez

Department of Electrical and Computer Engineering: Faculty Publications

A dual-network Cyber-physical Networking (CPN) testbed developed at the University of Nebraska-Lincoln is described. The CPN testbed consists of two geographically disparate wireless sensor networks connected by a traditional TCP/IP network and enables peer-to-peer communication between each sensor in the network. The functionality of the testbed is enhanced by a range of software tools that support remote programming and network monitoring, and real-time visualization of sensor data. The resulting architecture supports easy deployment and evaluation of applications for both traditional and interconnected wireless sensor networks. To demonstrate the features of this testbed, a novel ping application was developed and deployed …

Raiphy: Phylogenetic Classification Of Metagenomics Samples Using Iterative Refinement Of Relative Abundance Index Profiles, Ozkan U. Nalbantoglu, Samuel F. Way, Steven H. Hinrichs, Khalid Sayood

Department of Electrical and Computer Engineering: Faculty Publications

Background: Computational analysis of metagenomes requires the taxonomical assignment of the genome contigs assembled from DNA reads of environmental samples. Because of the diverse nature of microbiomes, the length of the assemblies obtained can vary between a few hundred bp to a few hundred Kbp. Current taxonomic classification algorithms provide accurate classification for long contigs or for short fragments from organisms that have close relatives with annotated genomes. These are significant limitations for metagenome analysis because of the complexity of microbiomes and the paucity of existing annotated genomes.

Results: We propose a robust taxonomic classification method, RAIphy, that …

Analysis Of The Accuracy-Latency-Energy Tradeoff For Wireless Embedded Camera Networks, Alvaro Pinto, Zhe Zhang, Xin Dong, Senem Velipasalar, Mehmet C. Vuran, M. Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

Wireless embedded smart cameras provide flexibility in camera deployment in terms of the locations and number of the cameras. However, these battery-powered embedded vision sensors have very limited energy, memory, and processing power. Energy consumption and latency are two major concerns in wireless embedded camera networks. In multi-camera tracking applications, the amount of data exchanged between cameras has an effect on the tracking accuracy, the energy consumption of the camera nodes and the latency. In this paper, we provide a detailed quantitative analysis of the accuracy-latency-energy tradeoff for overlapping and non-overlapping camera setups when different-sized data packets are transferred in …

Channel Coding Over Multiple Coherence Blocks With Queueing Constraints, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

This paper investigates the performance of wireless systems that employ finite-blocklength channel codes for transmission and operate under queueing constraints in the form of limitations on buffer overflow probabilities. A block fading model, in which fading stays constant in each coherence block and change independently between blocks, is considered. It is assumed that channel coding is performed over multiple coherence blocks. An approximate lower bound on the transmission rate is obtained from Feintein’s Lemma. This lower bound is considered as the service rate and is incorporated into the effective capacity formulation, which characterizes the maximum constant arrival rate that can …

On The Effective Capacity Of Two-Hop Communication Systems, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, two-hop communication between a source and a destination with the aid of an intermediate relay node is considered. Both the source and intermediate relay node are assumed to operate under statistical quality of service (QoS) constraints imposed as limitations on the buffer overflow probabilities. It is further assumed that the nodes send the information at fixed power levels and have perfect channel side information. In this scenario, the maximum constant arrival rates that can be supported by this two-hop link are characterized by finding the effective capacity. Through this analysis, the impact upon the throughput of having …

Energy Efficiency In The Low-Snr Regime Under Queueing Constraints And Channel Uncertainty, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

Energy efficiency of fixed-rate transmissions is studied in the presence of queueing constraints and channel uncertainty. It is assumed that neither the transmitter nor the receiver has channel side information prior to transmission. The channel coefficients are estimated at the receiver via minimum mean-square-error (MMSE) estimation with the aid of training symbols. It is further assumed that the system operates under statistical queueing constraints in the form of limitations on buffer violation probabilities. The optimal fraction of power allocated to training is identified. Spectral efficiency–bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity …