Open Access. Powered by Scholars. Published by Universities.®

Aerospace Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Discipline
Keyword
Publication Year

Articles 361 - 390 of 805

Full-Text Articles in Aerospace Engineering

Effects Of Magnetic Fields On Magnetohydrodynamic Cylindrical And Spherical Richtmyer-Meshkov Instability, Wouter Mostert, Vincent Wheatley, Ravi Samtaney, Dale I. Pullin Oct 2015

Effects Of Magnetic Fields On Magnetohydrodynamic Cylindrical And Spherical Richtmyer-Meshkov Instability, Wouter Mostert, Vincent Wheatley, Ravi Samtaney, Dale I. Pullin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effects of seed magnetic fields on the Richtmyer-Meshkov instability driven by converging cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Two different seed field configurations at various strengths are applied over a cylindrical or spherical density interface which has a single-dominant-mode perturbation. The shocks that excite the instability are generated with appropriate Riemann problems in a numerical formulation and the effect of the seed field on the growth rate and symmetry of the perturbations on the density interface is examined. We find reduced perturbation growth for both field configurations and all tested strengths. The extent of growth suppression …

Go to article

Coalescence-Induced Jumping Of Nanoscale Droplets On Super-Hydrophobic Surfaces, Zhi Liang, Pawel Keblinski Oct 2015

Coalescence-Induced Jumping Of Nanoscale Droplets On Super-Hydrophobic Surfaces, Zhi Liang, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Coalescence-Induced Jumping of Tens of Microns Size Droplets on Super-Hydrophobic Surfaces Has Been Observed in Both Experiments and Simulations. However, Whether the Coalescence-Induced Jumping Would Occur for Smaller, Particularly Nanoscale Droplets, is an Open Question. using Molecular Dynamics Simulations, We Demonstrate that in Spite of the Large Internal Viscous Dissipation, Coalescence of Two Nanoscale Droplets on a Super-Hydrophobic Surface Can Result in a Jumping of the Coalesced Droplet from the Surface with a Speed of a Few M/s. Similar to the Coalescence-Induced Jumping of Microscale Droplets, We Observe that the Bridge between the Coalescing Nano-Droplets Expands and Impacts the …

Go to article

Molecular Simulations And Lattice Dynamics Determination Of Stillinger-Weber Gan Thermal Conductivity, Zhi Liang, Ankit Jain, Alan J.H. Mcgaughey, Pawel Keblinski Sep 2015

Molecular Simulations And Lattice Dynamics Determination Of Stillinger-Weber Gan Thermal Conductivity, Zhi Liang, Ankit Jain, Alan J.H. Mcgaughey, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Bulk Thermal Conductivity of Stillinger-Weber (SW) Wurtzite GaN in the [0001] Direction at a Temperature of 300 K is Calculated using Equilibrium Molecular Dynamics (EMD), Non-Equilibrium MD (NEMD), and Lattice Dynamics (LD) Methods. While the NEMD Method Predicts a Thermal Conductivity of 166 ± 11 W/m·K, Both the EMD and LD Methods Predict Thermal Conductivities that Are an Order of Magnitude Greater. We Attribute the Discrepancy to Significant Contributions to Thermal Conductivity from Long-Mean Free Path Phonons. We Propose that the Grüneisen Parameter for Low-Frequency Phonons is a Good Predictor of the Severity of the Size Effects in NEMD …

Go to article

Experimental Investigations Of Dusty Spacecraft Charging At The Lunar Terminator, Kevin Chou, William Yu, Daoru Frank Han, Joseph J. Wang Sep 2015

Experimental Investigations Of Dusty Spacecraft Charging At The Lunar Terminator, Kevin Chou, William Yu, Daoru Frank Han, Joseph J. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An experimental investigation is conducted to understand the I-V characteristics and floating potential of a surface covered by varying amounts of dust in a plasma environment similar to that at the lunar terminator. I-V curves are measured to determine dust coverage effects on surface charging, and a non-contacting electrostatic voltmeter is used to measure dust surface charging. Results show that as dust coverage increases, the electric field created between the dust surface layer and conducting surface layer increases the possibility of arcing and breakdown.

Go to article

Exploitation Of Heterogeneity In Distributed Sensing: An Active-Passive Networked Multiagent Systems Approach, John Daniel Peterson, Tansel Yucelen, Girish Chowdhary, Suresh Kannan Jul 2015

Exploitation Of Heterogeneity In Distributed Sensing: An Active-Passive Networked Multiagent Systems Approach, John Daniel Peterson, Tansel Yucelen, Girish Chowdhary, Suresh Kannan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Most distributed sensing methods assume that the expected value of sensed information is same for all agents - ignoring differences in sensor capabilities due to, for example, environmental factors and sensors' quality and condition. In this paper, we present a distributed sensing framework to exploit heterogeneity in information provided about a dynamic environment using an active-passive networked multiagent systems approach. Specifically, this approach consists of agents subject to exogenous inputs (active agents) and agents without any inputs (passive agents). In addition, if an active agent senses a quantity accurately (resp., not accurately), then it is weighted high (resp., low) in …

Go to article

Adaptive Control With Nonlinear Reference Systems, Tansel Yucelen, Benjamin Gruenwald, Jonathan A. Muse, Gerardo De La Torre Jul 2015

Adaptive Control With Nonlinear Reference Systems, Tansel Yucelen, Benjamin Gruenwald, Jonathan A. Muse, Gerardo De La Torre

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Although reference systems with linear dynamics are common in the adaptive control literature, they can lead to limitations on the achievable closed-loop dynamical system performance. This is due to the fact that linear reference systems can only approximate the desired closed-loop behavior of nonlinear dynamical systems in narrow regions of the state-space. In this paper, we study a new adaptive control architecture for uncertain dynamical systems based on a nonlinear reference system. It is shown that the system error between the uncertain dynamical system and the nonlinear reference system asymptotically vanishes in steady-state, and its performance is guaranteed during the …

Go to article

Analysis And Design Of Adaptive Control Systems With Unmodeled Input Dynamics Via Multiobjective Convex Optimization, Mario Luca Fravolini, Tansel Yucelen, Jonathan Muse, Paolo Valigi Jul 2015

Analysis And Design Of Adaptive Control Systems With Unmodeled Input Dynamics Via Multiobjective Convex Optimization, Mario Luca Fravolini, Tansel Yucelen, Jonathan Muse, Paolo Valigi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A challenging problem for adaptive control systems is the accurate characterization of the transient response in the presence of dynamic uncertainties such as a partially known actuator. Considering an actuator modelled as a first order filter with an uncertain control effectiveness and using a projection mechanism for parameters adaptation, we show that the tracking error dynamics behaves as a linear system perturbed by bounded uncertainties. This brings the advantage that the stability analysis can be cast in terms of LMIs so that convex optimization tools can be used for analysis and design. In this framework we propose a mixed linear/adaptive …

Go to article

Consensus With Reduced Communication Links Via Relative Neighboring Velocity Information, Gerardo De La Torre, Tansel Yucelen Jul 2015

Consensus With Reduced Communication Links Via Relative Neighboring Velocity Information, Gerardo De La Torre, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a consensus protocol is introduced to virtually manipulate the communication topology of a given networked multiagent system - without adding physical edges to the graph. The proposed protocol achieves this objective by utilizing not only neighboring agents' relative position information but also their possibly delayed velocity information. It is shown that the stability of the proposed framework is not dependent on the possible time delay present in the neighboring velocity information. In addition, it is formally proven that utilization of the proposed consensus protocol is equivalent to the addition of virtual communication links in a standard consensus …

Go to article

Slip Length Crossover On A Graphene Surface, Zhi Liang, Pawel Keblinski Apr 2015

Slip Length Crossover On A Graphene Surface, Zhi Liang, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using Equilibrium and Non-Equilibrium Molecular Dynamics Simulations, We Study the Flow of Argon Fluid above the Critical Temperature in a Planar Nanochannel Delimited by Graphene Walls. We Observe that, as a Function of Pressure, the Slip Length First Decreases Due to the Decreasing Mean Free Path of Gas Molecules, Reaches the Minimum Value When the Pressure is Close to the Critical Pressure, and Then Increases with Further Increase in Pressure. We Demonstrate that the Slip Length Increase at High Pressures is Due to the Fact that the Viscosity of Fluid Increases Much Faster with Pressure Than the Friction Coefficient between …

Go to article

An Interoperable System For Automated Diagnosis Of Cardiac Abnormalities From Electrocardiogram Data, Thidarat Tinnakornsrisuphap, Richard E. Billo Mar 2015

An Interoperable System For Automated Diagnosis Of Cardiac Abnormalities From Electrocardiogram Data, Thidarat Tinnakornsrisuphap, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Electrocardiogram (ECG) data are stored and analyzed in different formats, devices, and computer platforms. As a result, ECG data from different monitoring devices cannot be displayed unless the user has access to the proprietary software of each particular device. This research describes an ontology and encoding for representation of ECG data that allows open exchange and display of ECG data in a web browser. The ontology is based on the Health Level Seven (HL7) medical device communication standard. It integrates ECG waveform data, HL7 standard ECG data descriptions, and cardiac diagnosis rules, providing a capability to both represent ECG waveforms …

Go to article

Effect Of A Dc Preionization Source On Energy Deposition In A Pulsed Inductive Plasma, Ryan A. Pahl, Joshua L. Rovey Jan 2015

Effect Of A Dc Preionization Source On Energy Deposition In A Pulsed Inductive Plasma, Ryan A. Pahl, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Go to article

Time-Resolved Argon Theta-Pinch Plasma Properties By Line Ratio Method With Collisional-Radiative Model, Warner C. Meeks, Joshua L. Rovey Jan 2015

Time-Resolved Argon Theta-Pinch Plasma Properties By Line Ratio Method With Collisional-Radiative Model, Warner C. Meeks, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Go to article

Electrospray Of An Energetic Ionic Liquid Monopropellant For Multi-Mode Micropropulsion Applications, Steven P. Berg, Joshua L. Rovey, Benjamin D. Prince, Shawn W. Miller, Raymond J. Bemish Jan 2015

Electrospray Of An Energetic Ionic Liquid Monopropellant For Multi-Mode Micropropulsion Applications, Steven P. Berg, Joshua L. Rovey, Benjamin D. Prince, Shawn W. Miller, Raymond J. Bemish

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The multi-mode chemical-electric propulsion capable energetic ionic liquid propellant [Emim][EtSO4]-HAN is electro sprayed in a 100 µm capillary emitter to test the electric-mode performance of the propellant. The ionic liquid exhibits stable electrospray emission in both cation and anion extraction modes at a nominal extraction voltage of 3400 V. Near field measurements of current and mass flow rate distribution are taken at flow rates from 0.19 nL/s to 3.06 nL/s. Total emission current, as measured by Faraday cup and integrated, increases from 754 nA to 3195 nA for cation emission and from 552 nA to 2012 nA for anion emission. …

Go to article

Numerical Simulations Of Surface Charging At The Lunar Terminator, Daoru Frank Han, Joseph J. Wang Jan 2015

Numerical Simulations Of Surface Charging At The Lunar Terminator, Daoru Frank Han, Joseph J. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A full-particle particle-in-cell (PIC) simulation model is developed to perform fully-kinetic simulations of surface-plasma interactions at the lunar terminator region. This model uses a non-homogeneous immersed-finite-element (IFE) solver to calculate the electric field discontinuity (flux jump) at the plasma-surface interface and surface charging for realistic lunar surface terrain. The simulation includes all plasma species, including the solar wind electrons and ions, as well as photoelectrons with real proton-to-electron mass ratio so the kinetic properties in the mesothermal flow are resolved. We present simulation results of surface charging around a lunar hill at the lunar terminator region.

Go to article

Performance Oriented Adaptive Architectures With Guaranteed Bounds, Benjamin Gruenwald, Tansel Yucelen, Mario Fravolini Jan 2015

Performance Oriented Adaptive Architectures With Guaranteed Bounds, Benjamin Gruenwald, Tansel Yucelen, Mario Fravolini

Mechanical and Aerospace Engineering Faculty Research & Creative Works

While adaptive control has been used in numerous applications to achieve given system stabilization or command following criteria, the ability to obtain a predictable transient performance is a challenging problem when there is no a priori knowledge about system uncertainties (e.g., their upper bounds and/or domains). In order to address this problem, a new method is presented in [1, 2] utilizing artificial basis functions in the update law of an adaptive control design. This approach is predicated on a gradient minimization procedure and achieves a predictable transient performance without inducing oscillations in the system response as the constant gain due …

Go to article

Damage Characteristics In 3d Stitched Composites With Various Stitch Parameters Under In-Plane Tension, Arief Yudhanto, Gilles Lubineau, Isaac Aguilar Ventura, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi Jan 2015

Damage Characteristics In 3d Stitched Composites With Various Stitch Parameters Under In-Plane Tension, Arief Yudhanto, Gilles Lubineau, Isaac Aguilar Ventura, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Three-dimensional (3D) reinforcement by stitching is effective in improving the impact resistance of composites. Stitching, however, adversely affects the composite's in-plane mechanical responses, and alters its damage mechanisms due to stitch-induced irregularities. We experimentally investigate the effect of two important stitch parameters, stitch density and thread diameter, on the damage characteristics of 3D stitched multidirectional composites under in-plane tension using X-ray radiography, X-ray micro-computed tomography and digital image correlation (DIC). Our study shows that composites stitched with thicker thread exhibit improved tensile strength due to effective hindrance of edge-delamination. We also found that stitch thread affects damage behaviors. A higher …

Go to article

Solid Waste As Renewable Source Of Energy: Current And Future Possibility In Libya, Tarek A. Hamad, Abdulhakim A. Agll, Yousif M. Hamad, John W. Sheffield Nov 2014

Solid Waste As Renewable Source Of Energy: Current And Future Possibility In Libya, Tarek A. Hamad, Abdulhakim A. Agll, Yousif M. Hamad, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Solid waste holds the greatest potential as biomass source in Libya. The rapid expansion of industry has led to increased urbanization and growing population. These factors have dramatically increased the amount of MSW (municipal solid waste) generated in Libya. However, issues related to environmentally sound MSW management - including waste decrease and clearance - have not been addressed sufficiently. This study presents an overview on solid waste that can be used as a source of bioenergy in Libya including MSW, ISW (industrial solid waste), and HSW (health care wastes) as biomass sources. The management of solid waste and valorization is …

Go to article

Study Of Energy Recovery And Power Generation From Alternative Energy Source, Abdulhakim Amer A. Agll, Yousif M. Hamad, Tarek A. Hamad, John W. Sheffield Nov 2014

Study Of Energy Recovery And Power Generation From Alternative Energy Source, Abdulhakim Amer A. Agll, Yousif M. Hamad, Tarek A. Hamad, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The energy requirement pattern of world is growing up and developing technology. The available sources, while exhausting and not friendly to the environment, are highly used. Looking at partial supply and different options of environment problems associated with usage, renewable energy sources are getting attention. MSW (Municipal solid waste) composition data had been collected from 1997 to 2009, in Benghazi Libya, to evaluate the waste enthalpy. An incinerator with capacity of 47,250 kg/h was confirmed to burn all the quantity of waste generated by the city through the next 15 years. Initial study was performed to investigate energy flow and …

Go to article

Design Of A Frequency-Selective Surface Strain Sensor, Edward C. Kinzel Sep 2014

Design Of A Frequency-Selective Surface Strain Sensor, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Frequency Selective Surfaces (FSS) have long been used in the RF/microwave community to control radar cross-section. The scattering parameters of the FSS form a signature which is a function of the frequency, element size and spacing, as well as the local electromagnetic environment. This paper considers a FSS as a strain sensor on the surface of a structural element. By interrogating the FSS with a series of polarized far-field measurements in a bistatic configuration the biaxial plane strain, including shear, can be resolved.

Go to article

Finite-Size Effects On Molecular Dynamics Interfacial Thermal-Resistance Predictions, Zhi Liang, Pawel Keblinski Aug 2014

Finite-Size Effects On Molecular Dynamics Interfacial Thermal-Resistance Predictions, Zhi Liang, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using Molecular Dynamics Simulations, We Study the Role of Finite Size Effects on the Determination of Interfacial Thermal Resistance between Two Solids Characterized by High Phonon Mean Free Paths. in Particular, We Will Show that a Direct, Heat Source-Sink Method Leads to Strong Size Effect, Associated with Ballistic Phonon Transport to and From, and Specular Reflections at the Simulation Domain Boundary. Lack of Proper Account for These Effects Can Lead to Incorrect Predictions About the Role of Interfacial Bonding and Structure on Interfacial Thermal Resistance. We Also Show that the Finite Size Effect Can Be Dramatically Reduced by Introduction of …

Go to article

Thermal Transport Across A Substrate-Thin-Film Interface: Effects Of Film Thickness And Surface Roughness, Zhi Liang, Kiran Sasikumar, Pawel Keblinski Aug 2014

Thermal Transport Across A Substrate-Thin-Film Interface: Effects Of Film Thickness And Surface Roughness, Zhi Liang, Kiran Sasikumar, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using Molecular Dynamics Simulations and a Model AlN-GaN Interface, We Demonstrate that the Interfacial Thermal Resistance RK (Kapitza Resistance) between a Substrate and Thin Film Depends on the Thickness of the Film and the Film Surface Roughness When the Phonon Mean Free Path is Larger Than Film Thickness. in Particular, When the Film (External) Surface is Atomistically Smooth, Phonons Transmitted from the Substrate Can Travel Ballistically in the Thin Film, Be Scattered Specularly at the Surface, and Return to the Substrate Without Energy Transfer. If the External Surface Scatters Phonons Diffusely, Which is Characteristic of Rough Surfaces, RK is Independent …

Go to article

Thermal Resistance At An Interface Between A Crystal And Its Melt, Zhi Liang, William J. Evans, Pawel Keblinski Jul 2014

Thermal Resistance At An Interface Between A Crystal And Its Melt, Zhi Liang, William J. Evans, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Non-Equilibrium Molecular Dynamics Simulations Are Used to Determine Interfacial Thermal Resistance (Kapitza Resistance) between a Crystal and its Melt for Three Materials Including Ar, H2O, and C8H 18 (Octane). the Simulation Results Show that the Kapitza Resistance at a Crystal-Melt Interface is Very Small and Thus Has a Negligible Effect on Thermal Transport Across the Crystal-Melt Interface. the Underlying Origins of This Behavior Are the Very Good Vibrational Property Match between the Two Materials Forming the Interface and Good Interfacial Bonding. the Result Also Indicates that the Commonly-Used Assumption that Temperature Profile is Continuous at the Crystal-Melt Interface is Valid …

Go to article

Curvature Induced Phase Stability Of An Intensely Heated Liquid, Kiran Sasikumar, Zhi Liang, David G. Cahill, Pawel Keblinski Jun 2014

Curvature Induced Phase Stability Of An Intensely Heated Liquid, Kiran Sasikumar, Zhi Liang, David G. Cahill, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We Use Non-Equilibrium Molecular Dynamics Simulations to Study the Heat Transfer Around Intensely Heated Solid Nanoparticles Immersed in a Model Lennard-Jones Fluid. We Focus Our Studies on the Role of the Nanoparticle Curvature on the Liquid Phase Stability under Steady-State Heating. for Small Nanoparticles We Observe a Stable Liquid Phase Near the Nanoparticle Surface, Which Can Be at a Temperature Well above the Boiling Point. Furthermore, for Particles with Radius Smaller Than a Critical Radius of 2 Nm We Do Not Observe Formation of Vapor Even above the Critical Temperature. Instead, We Report the Existence of a Stable Fluid Region …

Go to article

A Novel Asymptotic Expansion Homogenization Analysis For 3-D Composite With Relieved Periodicity In The Thickness Direction, Muhammad Ridlo Erdata Nasution, Naoyuki Watanabe, Atsushi Kondo, Arief Yudhanto Jun 2014

A Novel Asymptotic Expansion Homogenization Analysis For 3-D Composite With Relieved Periodicity In The Thickness Direction, Muhammad Ridlo Erdata Nasution, Naoyuki Watanabe, Atsushi Kondo, Arief Yudhanto

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A new asymptotic expansion homogenization analysis is proposed to analyze 3-D composite in which thermomechanical and finite thickness effects are considered. Finite thickness effect is captured by relieving periodic boundary condition at the top and bottom of unit-cell surfaces. The mathematical treatment yields that only 2-D periodicity (i.e. in in-plane directions) is taken into account. A unit-cell representing the whole thickness of 3-D composite is built to facilitate the present method. The equivalent in-plane thermomechanical properties of 3-D orthogonal interlock composites are calculated by present method, and the results are compared with those obtained by standard homogenization method (with 3-D …

Go to article

Effect Of Stitch Density On Fatigue Characteristics And Damage Mechanisms Of Stitched Carbon/Epoxy Composites, Arief Yudhanto, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi May 2014

Effect Of Stitch Density On Fatigue Characteristics And Damage Mechanisms Of Stitched Carbon/Epoxy Composites, Arief Yudhanto, Naoyuki Watanabe, Yutaka Iwahori, Hikaru Hoshi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effect of stitch density (SD) on fatigue life, stiffness degradation and fatigue damage mechanisms in carbon/epoxy (T800SC/XNRH6813) stitched using Vectran thread is presented in this paper. Moderately stitched composite (SD = 0.028/mm2; 'stitched 6 x 6') and densely stitched composite (SD = 0.111/mm2; 'stitched 3 x 3') are tested and compared with composite without stitch thread (SD = 0.0; 'unstitched'). The experiments show that the fatigue life of stitched 3 x 3 is moderately better than that of unstitched and stitched 6 x 6. Stitched 3 x 3 pattern is also able to postpone the …

Go to article

Frequency-Limited Adaptive Control Of A Generic Transport Model In The Presence Of System Uncertainty And Losses In Control Effectiveness, Gerardo De La Torre, Tansel Yucelen, Wassim M. Haddad, Eric N. Johnson Feb 2014

Frequency-Limited Adaptive Control Of A Generic Transport Model In The Presence Of System Uncertainty And Losses In Control Effectiveness, Gerardo De La Torre, Tansel Yucelen, Wassim M. Haddad, Eric N. Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

While adaptive control has been used in numerous applications to achieve system performance without excessive reliance on dynamical system models, the necessity of high-gain learning rates for safety-critical systems to achieve fast adaptation can be a serious limitation of most adaptive controllers. In order to address this problem, two novel adaptive control approaches developed recently aim to limit the bandwidth of the closed-loop adaptive control system in order to suppress the high-frequency content contained in the system error dynamics and adaptation algorithms. Specifically, this key feature of these frameworks allows for robust and fast adaptation by utilizing high-gain learning rates …

Go to article

The Origin Of Interferometric Effect Involving Surface Plasmon Polariton In Scattering Near-Field Scanning Optical Microscopy, Yan Li, Nan Zhou, Edward C. Kinzel, Xifeng Ren, Xianfan Xu Feb 2014

The Origin Of Interferometric Effect Involving Surface Plasmon Polariton In Scattering Near-Field Scanning Optical Microscopy, Yan Li, Nan Zhou, Edward C. Kinzel, Xifeng Ren, Xianfan Xu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Scattering near-field scanning optical microscopy (s-NSOM) has been developed to characterize optical near field with spatial resolution on the order of 10 nm. In this work we report investigation of the interferometric patterns commonly occurred in s-NSOM measurements. To reveal the origin of such interference patterns, a simple nano slit is used. Comparing the measured result with a simplified analytical model as well as full-field numerical simulations, it is shown that the interference pattern is predominantly formed by the in-plane component of incidence light and surface plasmon polariton (SPP) launched by the nano slit. This result helps to understand the …

Go to article

Femtosecond And Nanosecond Dual-Laser Optical Emission Spectroscopy Of Gas Mixtures, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai Feb 2014

Femtosecond And Nanosecond Dual-Laser Optical Emission Spectroscopy Of Gas Mixtures, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Method Employing an Integrated Femtosecond (Fs) and Nanosecond (Ns) Dual-Laser System Was Developed to Generate Plasma with Desired Radical Species from Gas Mixtures Via a Fs Laser Pulse and Then to Excite Selected Radical Species to Higher Electronic States using a Wavelength-Tunable Ns Laser Pulse. an Optical Spectrometer Was Used to Measure the Emission Spectra and Identify the Transition from the Excited Electronic State to the Ground State. the Proposed Technique Has Been Demonstrated for an N2-CO2 Mixture with Various Time Delays between the Two Fs and Ns Pulses. the Results Have Indicated that the Population of Selected Radical …

Go to article

Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson Jan 2014

Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper introduces an active-passive networked multiagent system framework, which consists of agents subject to exogenous inputs (active agents) and agents without any inputs (passive agents) and analyze its convergence using Lyapunov stability. Apart from the existing relevant literature, where either none of the agents are subject to exogenous inputs (i.e., average consensus problem) or all agents are subject to these inputs (i.e., dynamic average consensus problem), the key feature of our approach is that the states of all agents converge to the average of the exogenous inputs applied only to the active agents, where these inputs may or may …

Go to article

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.

Go to article

First Prev Next Last