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Articles 1 - 13 of 13
Full-Text Articles in Engineering
An Algorithmic Approach To Loop Shaping With Applications To Self-Tuning Control Systems, Zhiqiang Gao
An Algorithmic Approach To Loop Shaping With Applications To Self-Tuning Control Systems, Zhiqiang Gao
Electrical and Computer Engineering Faculty Publications
An algorithmic approach to feedback control design is introduced. It simplifies the existing iterative design process, which is often tedious, by reducing the design problem to solving a set of linear algebraic equations. The algorithmic nature of such an approach makes it attrative to not only off-line designs but also self-tuning control systems, where the compensators are continuously tuned on-line as the dynamics of the physical process vary with time. This is demonstrated in the example where the proposed algorithm is implemented for an industrial tension regulation system with successful simulation results. Extensions of the algorithm to …
Fault Tolerant Training For Optimal Interpolative Nets, Daniel J. Simon, Hossny El-Sherief
Fault Tolerant Training For Optimal Interpolative Nets, Daniel J. Simon, Hossny El-Sherief
Electrical and Computer Engineering Faculty Publications
The optimal interpolative (OI) classification network is extended to include fault tolerance and make the network more robust to the loss of a neuron. The OI net has the characteristic that the training data are fit with no more neurons than necessary. Fault tolerance further reduces the number of neurons generated during the learning procedure while maintaining the generalization capabilities of the network. The learning algorithm for the fault-tolerant OI net is presented in a recursive formal, allowing for relatively short training times. A simulated fault-tolerant OI net is tested on a navigation satellite selection problem
Influence Of Cr And W Alloying On The Fiber-Matrix Interfacial Shear-Strength In Cast And Directionally Solidified Sapphire Nial Composites, R. Asthana, R. Tiwari, Surendra N. Tewari
Influence Of Cr And W Alloying On The Fiber-Matrix Interfacial Shear-Strength In Cast And Directionally Solidified Sapphire Nial Composites, R. Asthana, R. Tiwari, Surendra N. Tewari
Chemical & Biomedical Engineering Faculty Publications
Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in …
Navigation Satellite Selection Using Neural Networks, Daniel J. Simon, Hossny El-Sherief
Navigation Satellite Selection Using Neural Networks, Daniel J. Simon, Hossny El-Sherief
Electrical and Computer Engineering Faculty Publications
The application of neural networks to optimal satellite subset selection for navigation use is discussed. The methods presented in this paper are general enough to be applicable regardless of how many satellite signals are being processed by the receiver. The optimal satellite subset is chosen by minimizing a quantity known as Geometric Dilution of Precision (GDOP), which is given by the trace of the inverse of the measurement matrix. An artificial neural network learns the functional relationships between the entries of a measurement matrix and the eigenvalues of its inverse, and thus generates GDOP without inverting a matrix. Simulation results …
Fuzzy Logic For Digital Phase-Locked Loop Filter Design, Daniel J. Simon, Hossny El-Sherief
Fuzzy Logic For Digital Phase-Locked Loop Filter Design, Daniel J. Simon, Hossny El-Sherief
Electrical and Computer Engineering Faculty Publications
The problem of robust phase-locked loop design has attracted attention for many years, particularly since the advent of the global positioning system. This paper proposes and demonstrates the use of a fuzzy PLL to estimate the time-varying phase of a sinusoidal signal. It is shown via simulation results that fuzzy PLL's offer performance comparable to analytically derived PLL's (e.g. Kalman filters and H∞ estimators) when the phase exhibits high dynamics and high noise. The fuzzy PLL rules are optimized using a gradient descent method and a genetic algorithm
Gps Modeling For Designing Aerospace Vehicle Navigation Systems, John J. Dougherty, Hossny El-Sherief, Daniel J. Simon, Gary A. Whitmer
Gps Modeling For Designing Aerospace Vehicle Navigation Systems, John J. Dougherty, Hossny El-Sherief, Daniel J. Simon, Gary A. Whitmer
Electrical and Computer Engineering Faculty Publications
The complexity of the design of a Global Positioning System (GPS) user segment, as well as the performance demanded of the components, depends on user requirements such as total navigation accuracy. Other factors, for instance the expected satellite/vehicle geometry or the accuracy of an accompanying inertial navigation system can also affect the user segment design. Models of GPS measurements are used to predict user segment performance at various levels. Design curves are developed which illustrate the relationship between user requirements, the user segment design, and component performance.
Optimal Sequence Estimation For Convolutionally Coded Signals With Binary Digital Modulation In Isi Channels, Fuqin Xiong
Optimal Sequence Estimation For Convolutionally Coded Signals With Binary Digital Modulation In Isi Channels, Fuqin Xiong
Electrical and Computer Engineering Faculty Publications
Decoding convolutional codes with binary digital modulation in intersymbol interference (ISI) channels is studied. The receiver structure is a whitened matched filter (WMF) whose transfer function is determined by the ISI channel. Decoding of the output sequence can be performed in two steps or one step. The two-step decoding first decodes the ISI corrupted coded sequence back to the ISI free coded sequence which is then decoded back to the uncoded message sequence. For one-step decoding, the entire encoder-channel-receiver system is modeled as a new encoder with combined memory length of the memory lengths of the original …
Development Of Nial-Based Intermetallic Alloys: Effect Of Chromium Addition, R. Tiwari, Surendra N. Tewari, R. Asthana, A. Garg
Development Of Nial-Based Intermetallic Alloys: Effect Of Chromium Addition, R. Tiwari, Surendra N. Tewari, R. Asthana, A. Garg
Chemical & Biomedical Engineering Faculty Publications
The mechanical behavior of dual-phase NiAl(Cr) microstructures, consisting of elongated primary NiAl grains aligned with an intergranular NiAl-Cr eutectic phase, produced by extrusion of a cast NiAl(Cr) alloy, has been examined. Chromium addition to create a dual phase NiAl-based aligned microstructure leads to large increases in the yield strength but no significant toughness improvement. This is achieved primarily by solid solution hardening and precipitation hardening. The constitutional hardening rate resulting from deviations from stoichiometry in the nickel-rich NiAl was estimated to be about 66 MPa per atomic per cent of nickel.
Influence Of Interfacial Reactions On The Fiber-Matrix Interfacial Shear-Strength In Sapphire Fiber-Reinforced Nial(Yb) Composites, Surendra N. Tewari, R. Asthana, R. Tiwari, R. R. Bowman, J. Smith
Influence Of Interfacial Reactions On The Fiber-Matrix Interfacial Shear-Strength In Sapphire Fiber-Reinforced Nial(Yb) Composites, Surendra N. Tewari, R. Asthana, R. Tiwari, R. R. Bowman, J. Smith
Chemical & Biomedical Engineering Faculty Publications
The influence of microstructure of the fiber-matrix interface on the interfacial shear strength, measured using a fiber-pushout technique, has been examined in a sapphire-fiber-reinforced NiAl(Yb) matrix composite under the following conditions: (1) as-fabricated powder metallurgy (PM) composites, (2) PM composites after solid-state heat treatment (HT), and (3) PM composites after directional solidification (DS). The fiber-pushout stress-displacement behavior consisted of an initial ''pseudoelastic'' region, wherein the stress increased linearly with displacement, followed by an ''inelastic'' region, where the slope of the stress-displacement plot decreased until a maximum stress was reached, and the subsequent gradual stress decreased to a ''frictional'' stress. Energy-dispersive …
Influence Of Fabrication Technique On The Fiber Pushout Behavior In A Sapphire-Reinforced Nial Matrix Composite, R. Asthana, R. R. Bowman, Surendra N. Tewari
Influence Of Fabrication Technique On The Fiber Pushout Behavior In A Sapphire-Reinforced Nial Matrix Composite, R. Asthana, R. R. Bowman, Surendra N. Tewari
Chemical & Biomedical Engineering Faculty Publications
Directional solidification (DS) of ''powder-cloth'' (PC) processed sapphire-NiAl composites was carried out to examine the influence of fabrication technique on the fiber-matrix interfacial shear strength, measured using a fiber-pushout technique. The DS process replaced the fine, equiaxed NiAl grain structure of the PC composites with an oriented grain structure comprised of large columnar NiAl grains aligned parallel to the fiber axis, with fibers either completely engulfed within the NiAl grains or anchored at one to three grain boundaries. The load-displacement behavior during the pushout test exhibited an initial ''pseudoelastic'' response, followed by an ''inelastic'' response, and finally a ''frictional'' sliding …
Lntracrystalline Diffusion Of Benzene In Silicalite : Effect Of Structural Heterogeneity, Dhananjai B. Shah, Chang-Jie Guo, David T. Hayhurst
Lntracrystalline Diffusion Of Benzene In Silicalite : Effect Of Structural Heterogeneity, Dhananjai B. Shah, Chang-Jie Guo, David T. Hayhurst
Chemical & Biomedical Engineering Faculty Publications
The sorption kinetics of benzene in silicalite have been measured gravimetrically using large silicalite crystals of sizes 350 µm × 105 µm × 105 µm and 270 µm × 70 µm × 70 µm in the temperature range 283–343 K. Experiments were performed under conditions that ensured isothermal operation with intracrystalline diffusion control. An analytical expression for the Darken's correction factor (δ In P/δ In a) was derived based on the Hill–de-Boer equation and was used to determine the variation of corrected diffusivity with concentration. The transport diffusivity varied significantly with the adsorbed-phase concentration but the …
Activity Coefficients Of Adsorbed Mixtures, Orhan Talu, Jianmin Li, Alan L. Myers
Activity Coefficients Of Adsorbed Mixtures, Orhan Talu, Jianmin Li, Alan L. Myers
Chemical & Biomedical Engineering Faculty Publications
Experimental and simulated data for adsorption of gas mixtures on energetically heterogeneous surfaces like activated carbon and zeolites exhibit negative deviations from ideality. The deviations are large in some cases, with activity coefficients at infinite dilution equal to 0.1 or less. Similar molecules form ideal mixtures, but molecules of different size or polarity are nonideal. Equations for bulk liquid mixtures (Wilson, Margules, etc.) do not apply to isobars for adsorbed mixtures. A two-constant equation for activity coefficients as a function of composition and spreading pressure is in good agreement with theory, simulation, and experiment.
Applying Neural Networks To Find The Minimum-Cost Coverage Of A Boolean Function, Pong P. Chu
Applying Neural Networks To Find The Minimum-Cost Coverage Of A Boolean Function, Pong P. Chu
Electrical and Computer Engineering Faculty Publications
To find a minimal expression of a boolean function includes a step to select the minimum cost cover from a set of implicants. Since the selection process is an NP-complete problem, to find an optimal solution is impractical for large input data size. Neural network approach is used to solve this problem. We first formalize the problem, and then define an ''energy function'' and map it to a modified Hopfield network, which will automatically search for the minima. Simulation of simple examples shows the proposed neural network can obtain good solutions most of the time.