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Distributional Fate Of Elements During The Synthesis Of Zeolites From South African Coal Fly Ash, Pieter W. Du Plessis, Tunde V. Ojumu, Ojo O. Fatoba, Richard O. Akinyeye, Leslie F. Petrik Jan 2014

Distributional Fate Of Elements During The Synthesis Of Zeolites From South African Coal Fly Ash, Pieter W. Du Plessis, Tunde V. Ojumu, Ojo O. Fatoba, Richard O. Akinyeye, Leslie F. Petrik

Mining Engineering Faculty Research & Creative Works

The synthesis of zeolites from South African coal fly ash has been deemed a viable solution to the growing economical strain caused by the disposal of ash in the country. Two synthesis routes have been studied thus far namely the 2-step method and the fusion assisted process. Fly ash contains several elements originating from coal which is incorporated in the ash during combustion. It is vital to determine the final destination of these elements in order to unveil optimization opportunities for scale-up purposes. The aim of this study was to perform a material balance study on both synthesis routes to …

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Environmental Fatigue Of Silicate Glasses In Humid Conditions, Zhongzhi Tang, Richard K. Brow Jan 2014

Environmental Fatigue Of Silicate Glasses In Humid Conditions, Zhongzhi Tang, Richard K. Brow

Materials Science and Engineering Faculty Research & Creative Works

Failure strains of commercial silica, soda-lime-silicate, and E-glass fibers were measured using two-point bending in room temperature humid air. Humidity dependence and dynamic fatigue behavior were studied, and the fatigue reaction orders in terms of humidity were determined. In the humidity range tested (~0.1% to ~100%), the dynamic fatigue parameters for silica and E-glass are found to be greater in lower humidity (~0.1% to ~10%), whereas the fatigue parameter for soda-lime-silicate is independent of humidity. The humidity dependence of failure strains for all three glasses was more pronounced in high humidity (~10% to ~100%) than in low humidity (~0.1% to …

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Crystallographic Orientation Of The Ε → Α' Martensitic (Athermal) Transformation In A Femnalsi Steel, S. T. Pisarik, D. C. Van Aken Jan 2014

Crystallographic Orientation Of The Ε → Α' Martensitic (Athermal) Transformation In A Femnalsi Steel, S. T. Pisarik, D. C. Van Aken

Materials Science and Engineering Faculty Research & Creative Works

The presence of a thermal ε- and α-martensite (α') in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two a thermal martensitic transformation described by γ → α' and γ → ε → α'. The Shoji-Nishiyama orientation relationship was observed between γ-austenite and ε-martensite, while α-martensite nucleated from γ-austenite exhibited a Kurdjumov-Sachs orientation relationship. Six crystallographic variants of α-martensite consisting of three twin-related variant pairs were observed in ε-bands. A planar parallelism of {0001}ε || {110}α' and a directional relation …

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Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos Jan 2014

Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.

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Thermotropic Phase Boundaries In Classic Ferroelectrics, Tom T. A. Lummen, Yijia Gu, Jianjun Wang Jan 2014

Thermotropic Phase Boundaries In Classic Ferroelectrics, Tom T. A. Lummen, Yijia Gu, Jianjun Wang

Materials Science and Engineering Faculty Research & Creative Works

High-performance piezoelectrics are lead-based solid solutions that exhibit a so-called morphotropic phase boundary, which separates two competing phases as a function of chemical composition; as a consequence, an intermediate low-symmetry phase with a strong piezoelectric effect arises. In search for environmentally sustainable lead-free alternatives that exhibit analogous characteristics, we use a network of competing domains to create similar conditions across thermal inter-ferroelectric transitions in simple, lead-free ferroelectrics such as BaTiO3 and KNbO3. Here we report the experimental observation of thermotropic phase boundaries in these classic ferroelectrics, through direct imaging of low-symmetry intermediate phases that exhibit large enhancements …

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Blackbox Macro-Modeling Of The Nonlinearity Based On Volterra Series Representation Of X-Parameters, Xiaoyan Y.Z. Xiong, Li (Lijun) J. Jiang, José E. Schutt-Ainé, Weng Cho Chew Jan 2014

Blackbox Macro-Modeling Of The Nonlinearity Based On Volterra Series Representation Of X-Parameters, Xiaoyan Y.Z. Xiong, Li (Lijun) J. Jiang, José E. Schutt-Ainé, Weng Cho Chew

Electrical and Computer Engineering Faculty Research & Creative Works

Volterra series representation is a powerful mathematical model for nonlinear devices. However, the difficulties in determining higher-order Volterra kernels limited its broader applications. This paper proposed a systematic approach that enables a convenient extraction of Volterra kernels from X-parameters for the first time. Then the Vandermonde method is employed to separate different orders of Volterra kernels at the same frequency, which leads to a highly efficient extraction process. The proposed Volterra series representation based on X-parameters is further benchmarked for verification. The proposed new algorithm is very useful for the blackbox macro-modeling of nonlinear devices and systems.

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A Calderón Preconditioner For The Electric Field Integral Equation With Layered Medium Green's Function, Yongpin P. Chen, Sheng Sun, Lijun Jiang, Weng Cho Chew Jan 2014

A Calderón Preconditioner For The Electric Field Integral Equation With Layered Medium Green's Function, Yongpin P. Chen, Sheng Sun, Lijun Jiang, Weng Cho Chew

Electrical and Computer Engineering Faculty Research & Creative Works

A Calderón preconditioner is developed for the analysis of electromagnetic scattering of perfect electrically conducting (PEC) objects embedded in a layered medium. The electric field integral equation (EFIE) is formulated with the kernel of layered medium Green's function to account for the effects from the multilayered background. The Calderón projector is derived based on the general source-field relationship and the extinction theorem for inhomogeneous environment in electromagnetic theory. The Calderón identities can be naturally deduced based on this projector, which is then leveraged to precondition the EFIE with layered kernel. An alternative implementation is then proposed to make the implementation …

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Magnetoelectric Dipole Antenna Arrays, Shulabh Gupta, Li (Lijun) Jun Jiang, Christophe Caloz Jan 2014

Magnetoelectric Dipole Antenna Arrays, Shulabh Gupta, Li (Lijun) Jun Jiang, Christophe Caloz

Electrical and Computer Engineering Faculty Research & Creative Works

A planar magnetoelectric (ME) dipole antenna array is proposed and demonstrated by both full-wave analysis and experiments. The proposed structure leverages the operation of composite right/left-handed transmission lines under balanced conditions to form high-gain magnetic radiators, combined with radial conventional electric radiators, where the overall structure is excited by a single differential feed. The traveling-wave-type nature of the proposed ME-dipole antenna enables the formation of directive arrays with high-gain characteristics and scanning capability. Peak gains of 10.84 dB and 5.73 dB are demonstrated for the electric dipole and magnetic-dipole radiation components, respectively. © 1963-2012 IEEE.

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A Rigorous Approach For The Radiated Emission Characterization Based On The Spherical Magnetic Field Scanning, Ping Li, Li (Lijun) Jun Jiang Jan 2014

A Rigorous Approach For The Radiated Emission Characterization Based On The Spherical Magnetic Field Scanning, Ping Li, Li (Lijun) Jun Jiang

Electrical and Computer Engineering Faculty Research & Creative Works

Electromagnetic radiated emissions from antennas, printed circuit boards (PCBs), and electronic devices are becoming increasingly critical to today's IC electromagnetic compatibility and interference properties. In this paper, a rigorous characterization approach is proposed. The electromagnetic field sampling over a spherical testing surface is applied to obtain the radiated magnetic field of the device under test (DUT) placed at the center of the sampling region. Using the dyadic Green's function (DGF) and Huygens' principle, the transformation from the sampled spherical tangential field to the far field is directly computed without resorting to the conventional inverse algorithm. The DGF considers the existence …

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Helmholtz Decomposition Based On Integral Equation Method For Electromagnetic Analysis, Xiaoyan Y.Z. Xiong, Wei E.I. Sha, Li (Lijun) Jun Jiang Jan 2014

Helmholtz Decomposition Based On Integral Equation Method For Electromagnetic Analysis, Xiaoyan Y.Z. Xiong, Wei E.I. Sha, Li (Lijun) Jun Jiang

Electrical and Computer Engineering Faculty Research & Creative Works

Helmholtz decomposition (HD) is a vector analysis fundamental tool and plays an important role in electromagnetics (EM) and microwave engineering. Instead of applying HD to the EM solving process, this article proposes an integral equation based rigorous HD process to extract and analyze the known EM field. It provides much clearer insight into field coupling and radiation mechanism that is valuable to electromagnetic interference (EMI) and electromagnetic compatibility (EMC) analysis. Compared to the loop-tree based decomposition that is a quasi-HD, the proposed method is rigorous and frequency-independent. The algorithm verification and its application to coupling and resonating problems are presented. …

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A Hybrid Time-Domain Discontinuous Galerkin-Boundary Integral Method For Electromagnetic Scattering Analysis, Ping Li, Yifei Shi, Li (Lijun) Jun Jiang, Hakan Baǧci Jan 2014

A Hybrid Time-Domain Discontinuous Galerkin-Boundary Integral Method For Electromagnetic Scattering Analysis, Ping Li, Yifei Shi, Li (Lijun) Jun Jiang, Hakan Baǧci

Electrical and Computer Engineering Faculty Research & Creative Works

A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer's shape and is located very close to its surface. Locally truncated domains can also be defined around …

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Model Order Reduction For Quantum Transport Simulation Of Band-To-Band Tunneling Devices, Jun Z. Huang, Lining Zhang, Weng Cho Chew, Chi Yung Yam, Li (Lijun) Jun Jiang, Guan Hua Chen, Mansun Chan Jan 2014

Model Order Reduction For Quantum Transport Simulation Of Band-To-Band Tunneling Devices, Jun Z. Huang, Lining Zhang, Weng Cho Chew, Chi Yung Yam, Li (Lijun) Jun Jiang, Guan Hua Chen, Mansun Chan

Electrical and Computer Engineering Faculty Research & Creative Works

Simulations of nanoelectronic devices with nonequilibrium Greens function are computationally very intensive, in particular, when combined with multiband approaches, such as the k p methods. To reduce the cost and make the simulation of realistic devices tractable, we have developed a model order reduction method for the simulation of hole transport in silicon nanowires using three- and six-band k p models. It is shown in this paper that, with a spurious band elimination process, the method can be readily extended to the eight-band case that enables us to simulate band-to-band tunneling devices. The method is demonstrated via constructing reduced models …

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Thermal-Electromagnetic Analysis Of Infrared Antennas, Edward C. Kinzel, Brian Slovick, James Ginn, Brian Lail, Glenn Boreman Jan 2014

Thermal-Electromagnetic Analysis Of Infrared Antennas, Edward C. Kinzel, Brian Slovick, James Ginn, Brian Lail, Glenn Boreman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Antenna-coupled Metal-Oxide-Metal (MOM) diodes have been demonstrated for sensing and proposed for energy harvesting at THz, infrared, and even visible frequencies. The design of the antenna allows engineering of the response of the device with respect to polarization, wavelength and angle of incidence. The classic understanding of the antenna coupled MOM diode is that the electric field generated by the antenna causes electrons to tunnel through the barrier oxide. This is supported by the fact that when the oxide separates metals with different work functions, a properly polarized field can produce an asymmetric tunnel current under zero bias. Losses in …

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Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi Jan 2014

Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive controllers are often criticized for the lack of clear and easy verification procedures that relate design parameters to time domain performance especially during transients. For this reason, it is a challenge to rigorously certify existing adaptive control algorithms. To that end, we propose a validation framework where stability and performance requirements are formulated in terms of Linear Matrix Inequalities. This brings the advantage that adaptive controller design and verification can be analyzed and optimized via the solution of a convex optimization whose objective is to guarantee the evolution of the error components within an a-priori specified domain. This approach …

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A Kalman Filter With Individual Control Factors For Echo Cancellation, Constantin Paleologu, Jacob Benesty, Silviu Ciochinǎ, Steven L. Grant Jan 2014

A Kalman Filter With Individual Control Factors For Echo Cancellation, Constantin Paleologu, Jacob Benesty, Silviu Ciochinǎ, Steven L. Grant

Electrical and Computer Engineering Faculty Research & Creative Works

In echo cancellation, the main goal is to recover the near-end signal from the error signal of the adaptive filter, which identifies the echo path. In this context, the Kalman filter represents a very appealing choice, since its basic criterion follows the minimization of the system misalignment (instead of the usual error-based cost function). In this paper, we propose a Kalman filter with individual control factors, in terms of using a different level of uncertainty for each coefficient of the filter. As compared to the basic Kalman filter (which imposes the same uncertainty for all the coefficients of the impulse …

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Linear Mimo Precoding In Jointly-Correlated Fading Multiple Access Channels With Finite Alphabet Signaling, Yongpeng Wu, Chao Kai Wen, Chengshan Xiao, Xiqi Gao, Robert Schober Jan 2014

Linear Mimo Precoding In Jointly-Correlated Fading Multiple Access Channels With Finite Alphabet Signaling, Yongpeng Wu, Chao Kai Wen, Chengshan Xiao, Xiqi Gao, Robert Schober

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we investigate the design of linear precoders for multiple-input multiple-output (MIMO) multiple access channels (MAC). We assume that statistical channel state information (CSI) is available at the transmitters and consider the problem under the practical finite alphabet input assumption. First, we derive an asymptotic (in the large-system limit) weighted sum rate (WSR) expression for the MIMO MAC with finite alphabet inputs and general jointly correlated fading. Subsequently, we obtain necessary conditions for linear precoders maximizing the asymptotic WSR and propose an iterative algorithm for determining the precoders of all users. In the proposed algorithm, the search space …

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Multibit Retention Registers For Power Gated Designs: Concept, Design, And Deployment, Yu Guang Chen, Hui Geng, Kuan Yu Lai, Yiyu Shi, Shih Chieh Chang Jan 2014

Multibit Retention Registers For Power Gated Designs: Concept, Design, And Deployment, Yu Guang Chen, Hui Geng, Kuan Yu Lai, Yiyu Shi, Shih Chieh Chang

Electrical and Computer Engineering Faculty Research & Creative Works

Retention registers have been widely used in power gated designs to store data during sleep mode. However, their excessive area and leakage power render it imperative to minimize the total retention storage size. The current industry practice replaces all registers with single bit retention ones, which significantly limits the design freedom and yields suboptimal designs. Toward this, for the first time in the literature, we propose the concept and the design of multibit retention registers, with which only selected registers need to be replaced. The technique can significantly reduce the number of bits that need to be stored and thus …

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Localization And Tracking Of Objects Using Cross-Correlation Of Shadow Fading Noise, M. R. Basheer, S. Jagannathan Jan 2014

Localization And Tracking Of Objects Using Cross-Correlation Of Shadow Fading Noise, M. R. Basheer, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

Multipath and shadow fading are the primary cause for positioning errors in a Received Signal Strength Indicator (RSSI) based localization scheme. While fading, in general, is detrimental to localization accuracy, cross-correlation and divergence properties of shadow fading residuals may be utilized to improve localization and tracking accuracy of mobile IEEE 802.15.4 transmitters. Therefore, this paper begins by presenting a stochastic filter that models the fast-changing multipath fading as a mean reverting Ornstein-Uhlenbeck (OU) process followed by a Generalized Auto Regressive Conditional Heteroskedasticity (GARCH) filtering to isolate the slow changing shadow fading residuals from measured RSSI values. Subsequently, a novel wireless …

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A Fault Prediction Scheme For Takagi-Sugeno Fuzzy Systems With Immeasurable Premise Variables And Disturbance, Balaje T. Thumati, Jagannathan Sarangapani Jan 2014

A Fault Prediction Scheme For Takagi-Sugeno Fuzzy Systems With Immeasurable Premise Variables And Disturbance, Balaje T. Thumati, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

As explained in the literature, it is very hard to measure premise variables of a Takagi-Sugeno (TS) fuzzy system. Therefore, in this paper, a fault detection and prediction (FDP) scheme is designed for a class of TS fuzzy systems with immeasurable (unknown) premise variables and external disturbances. A fault detection (FD) observer is designed to approximate the system output and the premise variables. Subsequently, a FD residual is generated by comparing the observer output with respect to the system output. The FD residual is evaluated to detect any faults in the system. Further, time-to-failure (TTF) of the TS fuzzy system …

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The Soft-Feedback Isi Canceller-Based Turbo Equalizer For Multilevel Modulations, Huang Lou, Chengshan Xiao Jan 2014

The Soft-Feedback Isi Canceller-Based Turbo Equalizer For Multilevel Modulations, Huang Lou, Chengshan Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we investigate the soft-feedback equalizer (SFE) proposed by Lopes et al. for multilevel modulations. The SFE is based on InterSymbol interference canceller structure and is compared to both soft-decision feedback turbo equalizer (SDFE) and the exact solution of MMSE linear equalizer (Exact-MMSE-LE) by means of EXIT chart analysis and BER simulations. Interesting results reveal that, for multilevel modulations, the SFE not only exhibits the same low complexity, low SNR threshold and fast convergence as SDFE but also reaches matched filter bound after a large number of iterations. © 2013 Springer Science + Business Media New York.

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An Accurate Frame Error Rate Approximation Of Coded Diversity Systems With Non-Identical Diversity Branches, Gang Wang, Jingxian Wu, Yahong Rosa Zheng Jan 2014

An Accurate Frame Error Rate Approximation Of Coded Diversity Systems With Non-Identical Diversity Branches, Gang Wang, Jingxian Wu, Yahong Rosa Zheng

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents an accurate approximation of the frame error rate (FER) of coded wireless communication systems with receiver diversity, such as single-input multiple-output (SIMO) systems with maximum ratio combining (MRC) or hybrid automatic repeat request (HARQ) systems with Chase combining. The signals at different diversity branches experience independent but non-identically distributed Rayleigh fading. The FER approximation is obtained with a threshold-based method. Specifically, the threshold value, which is critical to the FER approximation accuracy, is modeled as a linear function of the frame length in the log-domain, with the slope and intercept of the linear function determined by the …

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Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier Jan 2014

Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

For many control applications, identifying an optimal operating point by maximizing/minimizing a performance function is important. This paper applies the extremum-seeking method to nonaffine, nonlinear discrete-time systems stabilized by an optimal adaptive controller. First, a novel averaging method is used for the nonlinear discrete-time systems to show that their output unique extrema are stable equilibrium points. Then, a singular perturbation method in discrete time is employed to show that the overall closed loop system will dynamically converge to the extremum. The applicability of this scheme is numerically verified on a Homogeneous Charge Compression Ignition (HCCI) model validated experimentally and expressed …

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Converting An Old Machines Lab Into A Functioning Power Network With A Microgrid For Education, Md Rasheduzzaman, Badrul H. Chowdhury, Shyam Bhaskara Jan 2014

Converting An Old Machines Lab Into A Functioning Power Network With A Microgrid For Education, Md Rasheduzzaman, Badrul H. Chowdhury, Shyam Bhaskara

Electrical and Computer Engineering Faculty Research & Creative Works

As colleges prepare or revise their power engineering courses to include discussions on the smart grid, the microgrid, distributed energy sources and renewable energy resources, the need for new material suitable for inclusion in a typical 4-year undergraduate engineering course has never been more obvious. Toward this effort, an old machines lab was remodeled and converted into a small power network that can be operated in both grid-connected and grid-islanded microgrid modes. The intent of this paper is to devise laboratory experiments to supplement a course in conventional power systems analysis at the undergraduate level. During the remodeling process, two …

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Ambiguity Group Based Location Recognition For Multiple Power Line Outages In Smart Grids, Jie Wu, Jinjun Xiong, Yiyu Shi Jan 2014

Ambiguity Group Based Location Recognition For Multiple Power Line Outages In Smart Grids, Jie Wu, Jinjun Xiong, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

The efficient location recognition of multiple outage lines is critical to not only cascading failure elimination but also repair cost reduction. Most of existing methods, however, fail to handle location recognition well. This failure typically occurs because the methods cannot overcome three challenges: the very limited number of Phasor Measurement Units (PMUs), the high computational complexity, and the possibility of concurrent multiple outage lines. This paper presents an efficient algorithm inspired by the ambiguity group theory to recognize the most likely outage line locations with limited PMUs. Using IEEE 14-, 57-, and 118-bus system, the experimental study demonstrates that the …

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Optimization Of Transmission Conditions In Waveform Relaxation Techniques For Rc Circuits, Mohammad D. Al-Khaleel, Martin J. Gander, Albert E. Ruehli Jan 2014

Optimization Of Transmission Conditions In Waveform Relaxation Techniques For Rc Circuits, Mohammad D. Al-Khaleel, Martin J. Gander, Albert E. Ruehli

Electrical and Computer Engineering Faculty Research & Creative Works

Waveform relaxation techniques have become increasingly important with the wide availability of parallel computers with a large number of processors. A limiting factor for classical waveform relaxation, however, is the convergence speed for an important class of problems, especially if long time windows are considered. In contrast, the optimized waveform relaxation algorithm discussed in this paper is well suited to address this problem. Today several numerical analyses have shown that optimized waveform relaxation algorithms can overcome slow convergence over long time windows. However, the optimized waveform relaxation techniques require the determination of optimized parameters. In this paper, we present a …

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Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei Jan 2014

Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effects of oxidation on mechanical behavior of a cone sample of ZrB2-SiC ceramic under arc-jet test conditions is studied by a finite element (FE) model. First a steady-state heat transfer FE method was employed to conduct the thermal analysis and obtain the temperature distribution in the inner body of the cone. Then, resulting temperature distribution is applied to the thermomechanical finite element analysis to calculate the thermal stress distribution in the cone body. Due to the mismatch of material properties between the bulk ZrB2-SiC and its new products after oxidation, the outer oxide layers constrain the thermal deformation of …

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Soft-Decision Feedback Turbo Equalization For Ldpc-Coded Mimo Underwater Acoustic Communications, Amirhossein Rafati, Huang Lou, Chengshan Xiao Jan 2014

Soft-Decision Feedback Turbo Equalization For Ldpc-Coded Mimo Underwater Acoustic Communications, Amirhossein Rafati, Huang Lou, Chengshan Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a low-complexity turbo-detection scheme is proposed for single-carrier multiple-input-multiple-output (MIMO) underwater acoustic (UWA) communication systems that employ low-density parity-check (LDPC) channel coding. The proposed iterative soft-decision feedback equalization (SDFE) algorithm offers a novel approach to combat error propagation by utilizing the past soft decisions to mitigate InterSymbol interference. In addition, we utilize an iterative data detection and channel estimation scheme to reduce the pilot overhead used in the data communication system. Performance of the proposed detection scheme is demonstrated through extensive communication data from two undersea experiments. The results show that the proposed SDFE algorithm provides robust …

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Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey Jan 2014

Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-mode spacecraft micro propulsion systems which include a high-thrust chemical mode and high-specific impulse electric mode are assessed with specific reference to cube sat-sized satellite applications. Both cold gas Freon-14 propellant and ionic liquid chemical monopropellant modes were investigated alongside pulsed plasma, electrospray, and helicon electric thruster modes. Systems involving chemical monopropellants have the highest payload mass fractions for a reference mission of a 500 m/s delta-V and 6U sized cube sat for electric propulsion usage below 55% of total delta-V. For higher electric propulsion usage, cold gas thrusters delivered a higher payload mass fraction due to lower system inert …

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Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen Jan 2014

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting. Specifically, adaptive state feedback for output tracking control problem of MIMO nonlinear systems is studied and gain scheduled reference model system is used for generating desired state trajectories. Using convex optimization tools, a single Lyapunov matrix is computed for multiple linearization's near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference system. This approach guarantees stability of the closed loop gain scheduled system. Adaptive state feedback control scheme is then developed, and its …

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Approximate Dynamic Programming, Local Or Global Optimal Solution?, Ali Heydari, S. N. Balakrishnan Jan 2014

Approximate Dynamic Programming, Local Or Global Optimal Solution?, Ali Heydari, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The problem of global optimality analysis of approximate dynamic programming-based solutions is investigated in this study. Sufficient conditions for global optimality are obtained without requiring the state penalizing terms in the cost function or the functions representing the dynamics to be convex functions. Afterwards, the theoretical results are confirmed through a qualitative analysis of an example problem. © 2014 American Automatic Control Council.

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