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Articles 5701 - 5730 of 11138

Full-Text Articles in Engineering

Polynomial Chaos For The Computation Of Annual Energy Production In Wind Farm Layout Optimization, Santiago Padrón, Andrew P.J. Stanley, Jared Thomas, Juan Alonso, Andrew Ning Oct 2016

Polynomial Chaos For The Computation Of Annual Energy Production In Wind Farm Layout Optimization, Santiago Padrón, Andrew P.J. Stanley, Jared Thomas, Juan Alonso, Andrew Ning

Faculty Publications

Careful management of wake interference is essential to further improve Annual Energy Production (AEP) of wind farms. Wake effects can be minimized through optimization of turbine layout, wind farm control, and turbine design. Realistic wind farm optimization is challenging because it has numerous design degrees of freedom and must account for the stochastic nature of wind. In this paper we provide a framework for calculating AEP for any relevant uncertain (stochastic) variable of interest. We use Polynomial Chaos (PC) to efficiently quantify the effect of the stochastic variables—wind direction and wind speed—on the statistical outputs of interest (AEP) for wind …

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Heat Transfer Analysis Of An Oblique Jet Impingement Cooling On Cmc Rough Surface, Karthik Krishna Oct 2016

Heat Transfer Analysis Of An Oblique Jet Impingement Cooling On Cmc Rough Surface, Karthik Krishna

Doctoral Dissertations and Master's Theses

A Ceramic Matrix Composite is high strength and high temperature capability composite, utilized in components like heat shield of space vehicles, flame holders and disc brakes. To be used in both static and dynamic components of a future gas turbine engine and even with high temperature capabilities of these CMC components, convection cooling will still likely be required. The surface of the CMC varies significantly from traditional super-alloy used in a modern engine, with large level of roughness and significant three-dimensional waviness. These complex features will impact the behavior of the near wall flows, and affect the heat transfer rates …

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Special Issue: Selected Papers From Idetc 2015, Venkat N. Krovi, Andrew P. Murray, James Schmiedeler Oct 2016

Special Issue: Selected Papers From Idetc 2015, Venkat N. Krovi, Andrew P. Murray, James Schmiedeler

Mechanical and Aerospace Engineering Faculty Publications

This second IDETC Special Issue, containing 19 papers from researchers in seven countries on three continents, seeks to cap- ture the current interest topics and latest results from the 39th ASME Mechanisms and Robotics (M&R) conference. The topics span the synthesis and analysis of novel mechanisms and robots as well as their validation in a variety of applications. The papers are organized with contributions to the core theoretical methodol- ogies of M&R (five papers) appearing first. The application areas that follow are micro air vehicles (MAVs) (two papers), modular robotics (three papers), origami applications (three papers), medi- cal robotics (three …

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Anisoplanatic Electromagnetic Image Propagation Through Narrow Or Extended Phase Turbulence Using Altitude-Dependent Structure Parameter, Monish Ranjan Chatterjee, Ali Mohamed Oct 2016

Anisoplanatic Electromagnetic Image Propagation Through Narrow Or Extended Phase Turbulence Using Altitude-Dependent Structure Parameter, Monish Ranjan Chatterjee, Ali Mohamed

Electrical and Computer Engineering Faculty Publications

The effects of turbulence on anisoplanatic imaging are often modeled through the use of a sequence of phase screens distributed along the optical path. We implement the split-step wave algorithm to examine turbulence-corrupted images.

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A Maximum Entropy Approach To Identifying Important Statistical Moments To Best-Represent Spray Distribution Data, Cheng Chen Oct 2016

A Maximum Entropy Approach To Identifying Important Statistical Moments To Best-Represent Spray Distribution Data, Cheng Chen

Theses and Dissertations

To obtain accurate spray droplet size and velocity distributions, higher-order statistical moments are needed. The Maximum Entropy formalism has been successfully used to predict the motion of spray flow in different models. This work is mainly focused on the use of the fourth-order moment combinations to calculate droplet probability density functions using the Maximum Entropy Formalism. Beginning with the second-order moment combinations, Lagrange multipliers have been calculated subject to given moment constraints, defining the probability density function. All lower moments are included when calculating the possible different higher-order moment combinations. From the results, each moment combination generated a set of …

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Dynamics And Control Of Three-Dimensional Perching Maneuver Under Dynamic Stall Influence, Mir Alikhan Bin Mohammad Feroskhan Oct 2016

Dynamics And Control Of Three-Dimensional Perching Maneuver Under Dynamic Stall Influence, Mir Alikhan Bin Mohammad Feroskhan

Theses and Dissertations

Perching is a type of aggressive maneuver performed by the class ‘Aves’ species to attain precision point landing with a generally short landing distance. Perching capability is desirable on unmanned aerial vehicles (UAVs) due to its efficient deceleration process that potentially expands the functionality and flight envelope of the aircraft. This dissertation extends the previous works on perching, which is mostly limited to two-dimensional (2D) cases, to its state-of-the-art three-dimensional (3D) variety. This dissertation presents the aerodynamic modeling and optimization framework adopted to generate unprecedented variants of the 3D perching maneuver that include the sideslip perching trajectory, which ameliorates the …

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Effects Of Auditory Vection Speed And Directional Congruence On Perceptions Of Visual Vection, Isabella Alexis Gagliano Oct 2016

Effects Of Auditory Vection Speed And Directional Congruence On Perceptions Of Visual Vection, Isabella Alexis Gagliano

Psychology Theses & Dissertations

Spatial disorientation is a major contributor to aircraft mishaps. One potential contributing factor is vection, an illusion of self-motion. Although vection is commonly thought of as a visual illusion, it can also be produced through audition. The purpose of the current experiment was to explore interactions between conflicting visual and auditory vection cues, specifically with regard to the speed and direction of rotation. The ultimate goal was to explore the extent to which aural vection could diminish or enhance the perception of visual vection. The study used a 3 × 2 within-groups factorial design. Participants were exposed to three levels …

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Pocketqube Opportunity Mission: Vmo Mission, Robert J. Twiggs Sep 2016

Pocketqube Opportunity Mission: Vmo Mission, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "PocketQube Opportunity Mission: VMO Mission" from September 30, 2016.

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Lunar Icecube: Nasa Nextstep Lunar Cubesat Mission, Robert J. Twiggs Sep 2016

Lunar Icecube: Nasa Nextstep Lunar Cubesat Mission, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Lunar IceCube: NASA NEXTSTEP Lunar CubeSat Mission" from September 29, 2016.

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Experiential Learning Opportunities Through Nasa Stem Content Allows Greater Grass Root-Level Understanding Of The Present Day’S Extreme Climate Change Scenario, Nazrul I. Khandaker, Stanley Schleifer, Matthew Khargie Sep 2016

Experiential Learning Opportunities Through Nasa Stem Content Allows Greater Grass Root-Level Understanding Of The Present Day’S Extreme Climate Change Scenario, Nazrul I. Khandaker, Stanley Schleifer, Matthew Khargie

Publications and Research

The NASA MAA (MUREP Aerospace Academy) project at York College has demonstrated a track record of providing experiential learning opportunities (ELO) to its participating students. ELOs associated with MAA are designed to increase learners’ involvement, knowledge, comprehension and application of learning in one or more STEM subjects/disciplines. They involve inquiry-and-activity-based learning approaches designed for the level of the learner to inspire, engage, and educate while progressively challenging each student. ELO activities enable learners to acquire knowledge, understand what they have learned, and apply that knowledge through inquiry-based tasks. Specifically, we are prepared to address the following priority: Encourage, increase, and …

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Effective Integration Of Nasa Stem Curricula Is Allowing Students To Appreciate Earth Science Concepts, Nazrul I. Khandaker, Stanley Schleifer, Krishna Mahabir, Newrence Wills, Matthew Khargie Sep 2016

Effective Integration Of Nasa Stem Curricula Is Allowing Students To Appreciate Earth Science Concepts, Nazrul I. Khandaker, Stanley Schleifer, Krishna Mahabir, Newrence Wills, Matthew Khargie

Publications and Research

NASA Minority University Research and Education Project (MUREP) Aerospace Academy - MAA is a national, innovative activity designed to increase participation and retention of historically underserved and underrepresented K-12 youth in the STEM disciplines, particularly earth science and human exploration (HEO). HEO is dedicated to informing and educating the public about NASA's plans for a new era in space exploration. Utilization of NASA satellite images, online climate education, space mathematics and other earth science-related resources is allowing students to conduct basic research and prepare themselves for a New York City-wide science competition. In addition to offering school children a solid …

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Multispectral Optical Telescope Alignment Testing For Cryogenic Space Environment, Trent Newswander, Preston Hooser, James Champagne Sep 2016

Multispectral Optical Telescope Alignment Testing For Cryogenic Space Environment, Trent Newswander, Preston Hooser, James Champagne

Space Dynamics Laboratory Publications

Multispectral space telescopes with visible to long wave infrared spectral bands provide difficult alignment challenges. The visible channels require precision in alignment and stability to provide good image quality in short wavelengths. This is most often accomplished by choosing materials with near zero thermal expansion glass or ceramic mirrors metered with carbon fiber reinforced polymer (CFRP) that are designed to have a matching thermal expansion. The IR channels are less sensitive to alignment but they often require cryogenic cooling for improved sensitivity with the reduced radiometric background. Finding efficient solutions to this difficult problem of maintaining good visible image quality …

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Cavity Geometric Features And Entrainment Characterization Resulting From A Ballistically Induced Hydrodynamic Ram Event, Andrew J. Lingenfelter Sep 2016

Cavity Geometric Features And Entrainment Characterization Resulting From A Ballistically Induced Hydrodynamic Ram Event, Andrew J. Lingenfelter

Theses and Dissertations

Hydrodynamic Ram can cause damage to industrial and aircraft systems. The resulting transient spray increases the probability of fire. To better understand the driving mechanisms behind transient spray, internal, and external measurements of the cavity geometry, and entrained flow field were accomplished. Research determined cavity contraction and separation are pre-cursors to the initiation of the transient spray phases. The entrained flow measurement required development of a new and novel technique using a continuous wave laser and atomized water particles. The peak mass flow correlated well with cavity geometric features, such as cavity contraction. Using the mass flow, cavity diameter at …

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Optimal Control Of An Uninhabited Loyal Wingman, Clay J. Humphreys Sep 2016

Optimal Control Of An Uninhabited Loyal Wingman, Clay J. Humphreys

Theses and Dissertations

As researchers strive to achieve autonomy in systems, many believe the goal is not that machines should attain full autonomy, but rather to obtain the right level of autonomy for an appropriate man-machine interaction. A common phrase for this interaction is manned-unmanned teaming (MUM-T), a subset of which, for unmanned aerial vehicles, is the concept of the loyal wingman. This work demonstrates the use of optimal control and stochastic estimation techniques as an autonomous near real-time dynamic route planner for the DoD concept of the loyal wingman. First, the optimal control problem is formulated for a static threat environment and …

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The Scaling Of Loss Pathways And Heat Transfer In Small Scale Internal Combustion Engines, Joseph K. Ausserer Sep 2016

The Scaling Of Loss Pathways And Heat Transfer In Small Scale Internal Combustion Engines, Joseph K. Ausserer

Theses and Dissertations

Prior literature indicates fuel conversion efficiency and normalized power deteriorate increasingly rapidly with decreasing displacement, but does not fully reveal the driving losses. The literature also suggested that increasing losses relax the required fuel anti-knock index (AKI), but offered conflicting conclusions on the performance impact. This comprehensive experimental study of three, 28 cm3 to 85 cm3 displacement, commercial-off-the-shelf (COTS), two-stroke ICEs identified short-circuiting as having the most deleterious impact on COTS engine performance in this size range. Heat transfer losses were comparable to larger engines for displaced volumes greater than 10 cm3. An engine friction model …

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Improving Real-World Performance Of Vision Aided Navigation In A Flight Environment, Donald T. Venable Sep 2016

Improving Real-World Performance Of Vision Aided Navigation In A Flight Environment, Donald T. Venable

Theses and Dissertations

The motivation of this research is to fuse information from an airborne imaging sensor with information extracted from satellite imagery in order to provide accurate position when GPS is unavailable for an extended duration. A corpus of existing geo-referenced satellite imagery is used to create a key point database. A novel algorithm for recovering coarse pose using by comparing key points extracted from the airborne imagery to the reference database is developed. This coarse position is used to bootstrap a local-area geo-registration algorithm, which provides GPS-level position estimates. This research derives optimizations for existing local-area methods for operation in flight …

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Mechanical Properties And Fatigue Behavior Of Unitized Composite Airframe Structures At Elevated Temperature, Mohamed Noomen Sep 2016

Mechanical Properties And Fatigue Behavior Of Unitized Composite Airframe Structures At Elevated Temperature, Mohamed Noomen

Theses and Dissertations

The tension-tension fatigue behavior of a newly developed unitized composite material system was investigated. The unitized composite consisted of a polymer matrix composite (PMC) co-cured with a ceramic matrix composite (CMC). The PMC portion consisted of an NRPE high-temperature polyimide matrix reinforced with carbon fibers woven in an eight harness satin weave (8HSW). The CMC layer is a single-ply non-crimp 3D orthogonal weave composite consisting of ceramic matrix reinforced with glass fibers. In order to assess the performance and suitability of this composite for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions …

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Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza Sep 2016

Space Qualification Testing Of A Deployable Shape Memory Alloy Cubesat Antenna, Carl L. Kobza

Theses and Dissertations

Increasingly capable CubeSat missions require antenna with improved Radio Frequency performance over the traditional CubeSat antennas. Deployable quadrifilar helical antennas (QHA) enable an acceptable stowing volume and deploy to provide increased gain and bandwidth over traditional patch and dipole antennas. Extensive ground testing is required to ensure the antenna is space qualified and to characterize the antenna deployment in the space environment. AFIT requires a QHA to perform a future CubeSat geolocation mission and contracted Helical Communication Technologies (HCT) to design and manufacture a Shape Memory Alloy (SMA) L-band deployable QHA. Vibration, thermal vacuum, laser vibrometer, and Voltage Standing Wave …

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Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess Sep 2016

Adaptive Estimation And Heuristic Optimization Of Nonlinear Spacecraft Attitude Dynamics, Joshuah A. Hess

Theses and Dissertations

For spacecraft conducting on-orbit operations, changes to the structure of the spacecraft are not uncommon. These planned or unanticipated changes in inertia properties couple with the spacecraft's attitude dynamics and typically require estimation. For systems with time-varying inertia parameters, multiple model adaptive estimation (MMAE) routines can be utilized for parameter and state estimates. MMAE algorithms involve constructing a bank of recursive estimators, each assuming a different hypothesis for the systems dynamics. This research has three distinct, but related, contributions to satellite attitude dynamics and estimation. In the first part of this research, MMAE routines employing parallel banks of unscented attitude …

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Orbit Determination Using Vinti's Solution, Steven P. Wright Sep 2016

Orbit Determination Using Vinti's Solution, Steven P. Wright

Theses and Dissertations

Orbital altitudes congested with spacecraft and debris combined with recent collisions have all but negated the Big Sky Theory. As the sheer number of orbital objects to track grows unbounded so does interest in prediction methods that are rapid and minimally computational. Claimed as the \other solvable solution, the recently completed solution too orbital motion about the earth, based on Vinti's method and including the major effects of the equatorial bulge, opens up the prospect of much more accurate analytical models for space situational awareness. A preliminary examination of this solution is presented. A numerical state transition matrix is found …

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From Xst To F-117a, Alan Brown Sep 2016

From Xst To F-117a, Alan Brown

ERAU Prescott Aviation History Program

Learn the remarkable story of stealth technology from the man often referred to as “Mr. Stealth.” From 1975-1989 Alan Brown was a member of Lockheed “Skunk Works”, becoming program manager & chief engineer for the F-117A Stealth Fighter from initial concept until the first production aircraft was built, 1978 to 1982. Hear the inside story of the many challenges faced by the stealth program and how they were solved.

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Pocketcubes/Cubesats On Antares, Robert J. Twiggs, Walter Holemans, Michael Bitzer Sep 2016

Pocketcubes/Cubesats On Antares, Robert J. Twiggs, Walter Holemans, Michael Bitzer

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs, Walter Holmans, and Michael Bitzer titled "PocketCubes/CubeSats on Antares" from September 6, 2016.

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Experimental Investigation On Flow Characteristics Of A Four-Wing Micro Air Vehicle, Lisong Shi, Chunkit Uy, Shih K. Huang, Zifeng Yang, George P.G. Huang, Chihyung Wen Sep 2016

Experimental Investigation On Flow Characteristics Of A Four-Wing Micro Air Vehicle, Lisong Shi, Chunkit Uy, Shih K. Huang, Zifeng Yang, George P.G. Huang, Chihyung Wen

Mechanical and Materials Engineering Faculty Publications

The aim of current research work on micro air vehicles is to realize their autonomous control, i.e. building a library for a lookup table that would apply to micro electronics. In doing so, comprehensive flight tests need to be carried out. In this study, a four-wing flapping MAV is built and a multi-discipline approach is used to design the MAV model. Precision manufacturing technology is introduced here. The finished micro air vehicle has a weight of 8 g and is tested for flight by remote control. The micro air vehicle can perform both hovering and forward flight with high maneuverability. …

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High-Frequency Instabilities Of Stationary Crossflow Vortices In A Hypersonic Boundary Layer, Fei Li, Meelan Choudhari, Pedro Paredes-Gonzalez, Lian Duan Sep 2016

High-Frequency Instabilities Of Stationary Crossflow Vortices In A Hypersonic Boundary Layer, Fei Li, Meelan Choudhari, Pedro Paredes-Gonzalez, Lian Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Hypersonic boundary layer flows over a circular cone at moderate incidence angle can support strong crossflow instability in between the windward and leeward rays on the plane of symmetry. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite-amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7° half-angle circular cone in a Mach 6 free stream. The analysis is based on …

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Experimental And Numerical Investigations Of Dust Effects On Surface Charging In Plasma, Kevin Chou, Daoru Frank Han, Joseph J. Wang Sep 2016

Experimental And Numerical Investigations Of Dust Effects On Surface Charging In Plasma, Kevin Chou, Daoru Frank Han, Joseph J. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A series of 3-D, fully kinetic particle-in-cell (PIC) simulations were performed to simulate mesothermal plasma flow self-consistently with surface charging. Simulation results of plasma charging of a conducting surface covered by a thin dust layer in a plasma of cold ions and thermal electrons are presented. The surface potentials and potentials inside the dust layer are compared with experimental results. Results show that a layer of dust over a conducting surface creates a capacitance, which drives the surface more negative with respect to the ambient plasma.

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Propulsion Theory Of Flapping Airfoils, Comparison With Computational Fluid Dynamics, Doug F. Hunsaker, W. F. Phillips Sep 2016

Propulsion Theory Of Flapping Airfoils, Comparison With Computational Fluid Dynamics, Doug F. Hunsaker, W. F. Phillips

Mechanical and Aerospace Engineering Faculty Publications

It is shown that the time-dependent aerodynamic forces acting on a flapping airfoil in forward flight are functions of both axial and normal reduced frequencies. The axial reduced frequency is based on the chord length, and the normal reduced frequency is based on the plunging amplitude. Furthermore, the time-dependent aerodynamic forces are related to two Fourier coefficients, which are evaluated here from computational results. Correlation equations for these Fourier coefficients are obtained from a large number of grid- and time-step-resolved inviscid computational-fluid-dynamics solutions, conducted over a range of both axial and normal reduced frequencies. The correlation results can be used …

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Experimentation Of Mode I And Mode Ii Fracture Of Uni-Directional Composites And Finite Element Analysis Of Mode I Fracture Using Cohesive Contact, Joseph Daniel Garrett Sep 2016

Experimentation Of Mode I And Mode Ii Fracture Of Uni-Directional Composites And Finite Element Analysis Of Mode I Fracture Using Cohesive Contact, Joseph Daniel Garrett

Master's Theses

As the use of fiber-reinforced composites has increased over the decades, so has the need to understand the complexity of their failure mechanisms as engineers seek to improve the damage tolerance of composite laminated structures. One of the most prevalent and limiting mode of failure within composite laminates is delamination, since it not only reduces a structures stiffness and strength, but can be very difficult to detect without the use of special non-destructive equipment. Industry testing organizations have utilized several fracture tests in order to characterize the fracture toughness of composite materials under different loading conditions. For this research, ASTM …

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Numerical Modeling Of Dust Dynamics Around Small Asteroids, William Yu, Joseph J. Wang, Daoru Frank Han Sep 2016

Numerical Modeling Of Dust Dynamics Around Small Asteroids, William Yu, Joseph J. Wang, Daoru Frank Han

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Dynamics of dust transport around an airless body has been a focused area of research in recent years, however, various challenging aspects still remain to be addressed. This paper presents an investigation of charged dust transport and distribution around small asteroids utilizing a full particle Particle-in-Cell (PIC) model to simulate plasma flow around an asteroid and calculate surface charging self-consistently from charge deposition on asteroid. Material properties of asteroid are also explicitly included in the simulation. PIC simulation results are fed into a 3D dust dynamics model to simulate charged dust levitation, transport and distribution. In addition to electrostatic and …

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A Hybrid Optimization Technique Applied To The Intermediate-Target Optimal Control Problem, Clay J. Humphreys, Richard G. Cobb, David R. Jacques, Jonah A. Reeger Aug 2016

A Hybrid Optimization Technique Applied To The Intermediate-Target Optimal Control Problem, Clay J. Humphreys, Richard G. Cobb, David R. Jacques, Jonah A. Reeger

Faculty Publications

The DoD has introduced the concept of Manned-Unmanned Teaming, a subset of which is the loyal wingman. Optimal control techniques have been proposed as a method for rapidly solving the intermediate-target (mid-point constraint) optimal control problem. Initial results using direct orthogonal collocation and a gradient-based method for solving the resulting nonlinear program reveals a tendency to converge to or to get `stuck’ in locally optimal solutions. The literature suggested a hybrid technique in which a particle swarm optimization is used to quickly find a neighborhood of a more globally minimal solution, at which point the algorithm switches to a gradient-based …

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Citizensatellite: Low Cost Missions For The Unordinary Innovator, Robert J. Twiggs, Amin Djamshidpour, Ted Tagami, Tony So Aug 2016

Citizensatellite: Low Cost Missions For The Unordinary Innovator, Robert J. Twiggs, Amin Djamshidpour, Ted Tagami, Tony So

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Robert Twiggs, Amin Djamshidpour, Ted Tagami, and Tony Sotitled "CitizenSatellite: Low Cost Missions for the Unordinary Innovator" from August 19, 2016.

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