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- Adaptive Control (7)
- Control System Synthesis (4)
- Learning Systems (4)
- Iterative Methods (3)
- Neurocontrollers (3)
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- Optimal Control (3)
- Combustion chambers (2)
- Feedback (2)
- Motion Control (2)
- Nonlinear Control Systems (2)
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- 3D Modeling (1)
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- Adaptive control (1)
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- Arc Welding (1)
- Attitude control (1)
- Autoignition; Cool flames; Microgravity; Thermokinetic oscillations; Wang-Mou model (1)
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- Black and brown birnessite particles (1)
- Bluff bodies (1)
- Boundary-Value Problems (1)
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- Mechanical and Aerospace Engineering Faculty Research & Creative Works (17)
- All Graduate Theses and Dissertations, Spring 1920 to Summer 2023 (2)
- Electrical and Computer Engineering Faculty Research & Creative Works (2)
- Faculty Publications - Biomedical, Mechanical, and Civil Engineering (2)
- Mechanical & Aerospace Engineering Faculty Publications (2)
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- Theses and Dissertations (2)
- Computer Science Faculty Research & Creative Works (1)
- Dissertations (1)
- Faculty Publications (1)
- Faculty Publications and Other Works -- Mechanical, Aerospace and Biomedical Engineering (1)
- Fred and Harriet Cox Senior Design Competition Projects (1)
- Graduate Theses, Dissertations, and Problem Reports (1)
- Mechanical & Aerospace Engineering Theses & Dissertations (1)
- Mechanical Engineering Faculty Publications (1)
- Mechanical Engineering Faculty Research and Publications (1)
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Articles 1 - 30 of 37
Full-Text Articles in Mechanical Engineering
Atomistic-Based Finite Element Simulation Of Carbon Nanotubes, Yang Yang
Atomistic-Based Finite Element Simulation Of Carbon Nanotubes, Yang Yang
Dissertations
Since first found in the form of multi-walled carbon nanotubes (MWNTs) by Iijima(1991), carbon nanotube (CNT) for its outstanding and unique properties have gained overwhelming attentions from across the spectrum of the science and engineering fields. CNTs are structurally perfect, small size, low density, high stiffness, high strength (Qian et al., 2002), and their electronic properties depend on the particular distortion as well as the initial tube diameter and chirality, ranging from narrow-gap or moderate-gap semiconducting to metallic (Pantano et al., 2004b), which can be utilized in nanoscale sensors and devices. These appealing characteristics provide strong drives for the possible …
Determination Of Vibrational Energy Levels And Transition Dipole Moments Of Co2 Molecules By Density Functional Theory, Zhi Liang, Hai-Lung Tsai
Determination Of Vibrational Energy Levels And Transition Dipole Moments Of Co2 Molecules By Density Functional Theory, Zhi Liang, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An Efficient Method is Presented to Calculate the Intra-Molecular Potential Energies and Electrical Dipole Moments of CO2 Molecules at the Electronic Ground State by Solving the Kohn-Sham (KS) Equation for a Total of 101 992 Nuclear Configurations. the Projector-Augmented Wave (PAW) Exchange-Correlation Potential Functionals and Plane Wave (PW) Basis Functions Were Used in Solving the KS Equation. the Calculated Intra-Molecular Potential Function Was Then Included in the Pure Vibrational Schrödinger Equation to Determine the Vibrational Energy Eigen Values and Eigen Functions. the Vibrational Wave Functions Combined with the Calculated Dipole Moment Function Were Used to Determine the Transition Dipole Moments. …
Modeling, Designing, Fabricating, And Testing Of Channel Panel Flat Plate Heat Pipes, James R. Harris
Modeling, Designing, Fabricating, And Testing Of Channel Panel Flat Plate Heat Pipes, James R. Harris
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Flat plate heat pipes are very efficient passive two-phase heat transport devices. Their high efficiency and low mass are desirable in the aerospace and electronics industries. The highly competitive nature of the thermal management industry results in little awareness of the capabilities of at plate heat pipes, which has resulted in only a few applications of the technology. In the year 2000 a research and development project sponsored by Space Dynamics Laboratory was launched to investigate building carbon-based at heat pipes. The flat configuration is desireable to incorporate many components onto one thermal management system. Development led to the adoption …
Angles-Only Navigation For Autonomous Orbital Rendezvous, David Charles Woffinden
Angles-Only Navigation For Autonomous Orbital Rendezvous, David Charles Woffinden
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The proposed thesis of this dissertation has both a practical element and theoretical component which aim to answer key questions related to the use of angles-only navigation for autonomous orbital rendezvous. The first and fundamental principle to this work argues that an angles-only navigation filter can determine the relative position and orientation (pose) between two spacecraft to perform the necessary maneuvers and close proximity operations for autonomous orbital rendezvous. Second, the implementation of angles-only navigation for on-orbit applications is looked upon with skeptical eyes because of its perceived limitation of determining the relative range between two vehicles. This assumed, yet …
A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai
A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. by combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted …
Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai
Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as …
High Bandwidth Control Of Precision Motion Instrumentation, Douglas A. Bristow, Jingyan Dong, Andrew G. Alleyne, Srinivasa M. Salapaka, Placid M. Ferreira
High Bandwidth Control Of Precision Motion Instrumentation, Douglas A. Bristow, Jingyan Dong, Andrew G. Alleyne, Srinivasa M. Salapaka, Placid M. Ferreira
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant …
Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu
Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication. Due to effects such as the air bubble release, agglomerate breakdown, change in paste properties during extrusion as a result of liquid phase migration, etc., the extrusion force is difficult to control. In this paper, an adaptive controller is proposed to regulate the extrusion force. Recursive Least Squares is used to estimate extrusion force model parameters during fabrication and a low-order control scheme capable of tracking general reference trajectories is designed …
Inter-Frequency Bias Estimation For The Gps Monitor Station Network, Donny Holaschutz, Robert H. Bishop, R. Benjamin Harris, Brian Tolman
Inter-Frequency Bias Estimation For The Gps Monitor Station Network, Donny Holaschutz, Robert H. Bishop, R. Benjamin Harris, Brian Tolman
Mechanical Engineering Faculty Research and Publications
The inter-frequency bias (IFB) is present in all dual frequency combinations of GPS pseudorange and carrier phase observables. It is caused by the path dependent signal delays in both the satellite and receiver. That delay can be directly measured for a space vehicle prior to launch, or for a ground based receiver prior to its being used in the field. However the bias is known to drift, and monitoring the delay estimate by direct measurement is time consuming for ground based receivers and impossible for deployed space vehicles. Hansen (2002) examined the observability of IFB through a global model of …
Reinforcement Learning Based Dual-Control Methodology For Complex Nonlinear Discrete-Time Systems With Application To Spark Engine Egr Operation, Peter Shih, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Reinforcement Learning Based Dual-Control Methodology For Complex Nonlinear Discrete-Time Systems With Application To Spark Engine Egr Operation, Peter Shih, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Electrical and Computer Engineering Faculty Research & Creative Works
A novel reinforcement-learning-based dual-control methodology adaptive neural network (NN) controller is developed to deliver a desired tracking performance for a class of complex feedback nonlinear discrete-time systems, which consists of a second-order nonlinear discrete-time system in nonstrict feedback form and an affine nonlinear discrete-time system, in the presence of bounded and unknown disturbances. For example, the exhaust gas recirculation (EGR) operation of a spark ignition (SI) engine is modeled by using such a complex nonlinear discrete-time system. A dual-controller approach is undertaken where primary adaptive critic NN controller is designed for the nonstrict feedback nonlinear discrete-time system whereas the secondary …
Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis
Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper traces the development of neural-network (NN)-based feedback controllers that are derived from the principle of adaptive/approximate dynamic programming (ADP) and discusses their closed-loop stability. Different versions of NN structures in the literature, which embed mathematical mappings related to solutions of the ADP-formulated problems called “adaptive critics” or “action-critic” networks, are discussed. Distinction between the two classes of ADP applications is pointed out. Furthermore, papers in “model-free” development and model-based neurocontrollers are reviewed in terms of their contributions to stability issues. Recent literature suggests that work in ADP-based feedback controllers with assured stability is growing in diverse forms.
A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu
A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a novel method of contour reconstruction from dexel data solving the shape anomalies for the complex geometry in virtual sculpting. Grouping and traversing processes are developed to find connectivity between dexels along every two adjacent rays. After traveling through all the rays on one slice, sub-boundaries are connected into full boundaries which are desired contours. The complexity of the new method has been investigated and determined as O(n). We also demonstrate the ability of the described method for viewing a sculpted model from different directions.
Laser-Induced Fluorescence And Performance Analysis Of The Ultra-Compact Combustor, Patrick J. Lakusta
Laser-Induced Fluorescence And Performance Analysis Of The Ultra-Compact Combustor, Patrick J. Lakusta
Theses and Dissertations
The AFIT Combustion Optimization and Analysis Laser (COAL) lab’s modular design and state-of-the-art diagnostic systems make it a flexible and important facility for the analysis of combustion processes. The objectives of the current research are to install several enhancements in the lab, validate the laser diagnostic system, characterize the igniter for AFIT’s Ultra-Compact Combustor (UCC) sections, and perform a non-intrusive laser diagnostic, performance, and high-speed video analysis of a flat-cavity UCC section. Validation of the laser system was accomplished using OH Planar Laser-Induced Fluorescence (PLIF) in a laminar hydrogen-air flame produced by a Hencken burner. Results are compared to previous …
Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow
Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In this work we examine the performance of iterative learning control (ILC) for systems with non-repeating disturbances and random noise. Single-input, single- output linear time-invariant systems and iteration-invariant learning filters are considered. We find that a tradeoff exists between the convergence rate and converged error spectrum. Optimal filter designs, which are dependant on the disturbance and noise spectra, are developed. We also present simple design guidelines for the case when explicit models of disturbance and noise spectra are not available. A numerical design example is presented.
Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan
Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In literature leader - follower strategy has been used extensively for formation control of car-like mobile robots with the control law being derived from the kinematics. This paper takes it a step further and a nonlinear control law is derived using Lyapunov analysis for formation control of car-like mobile robots using robot dynamics. Controller is split into two parts. The first part is the development of a velocity controller for the follower from the error kinematics (linear and angular). The second part involves the use of the dynamics of the robot in the development of a torque controller for both …
Adaptive Quaternion Control Of A Miniature Tailsitter Uav, Nathan B. Knoebel, Timothy W. Mclain
Adaptive Quaternion Control Of A Miniature Tailsitter Uav, Nathan B. Knoebel, Timothy W. Mclain
Faculty Publications
The miniature tailsitter is a unique aircraft with inherent advantages over typical unmanned aerial vehicles. With the capabilities of both hover and level flight, these small, portable systems can produce efficient maneuvers for enhanced surveillance and autonomy with little threat to surroundings and the system itself. Such vehicles create control challenges due to the two different flight regimes. These challenges are addressed with a computationally efficient adaptive quaternion control algorithm. A backstepping method for model cancellation and consistent tracking of reference model attitude dynamics is derived. This is used in conjunction with a regularized data-weighting recursive least-squares algorithm for the …
Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow
Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In this paper we examine the robustness of norm optimal ILC with quadratic cost criterion for discrete-time, linear time-invariant, single-input single-output systems. A bounded multiplicative uncertainty model is used to describe the uncertain system and a sufficient condition for robust monotonic convergence is developed. We find that, for sufficiently large uncertainty, the performance weighting can not be selected arbitrarily large, and thus overall performance is limited. To maximize available performance, a time-frequency design methodology is presented to shape the weighting matrix based on the initial tracking error. The design is applied to a nanopositioning system and simulation results are presented.
Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne
Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In many manufacturing applications contour tracking is more important than individual axis tracking. Many control techniques, including iterative learning control (ILC), target individual axis error. Because individual axis error only indirectly relates to contour error, these approaches may not be very effective for contouring applications. Cross-coupled ILC (CCILC) is a variation on traditional ILC that targets the contour tracking directly. In contour trajectories with rapid changes, high frequency control is necessary in order to meet tracking requirements. This paper presents an improved CCILC that uses a linear time-varying (LTV) filter to provide high frequency control for short durations. The improved …
Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan
Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a systematic approach to solve for the optimal control of a variable-time impulsive system. First, optimality condition for a variable-time impulsive system is derived using the calculus of variations method. Next, a single network adaptive critic technique is proposed to numerically solve for the optimal control and the detailed algorithm is presented. Finally, two examples-one linear and one nonlinear-are solved applying the conditions derived and the algorithm proposed. Numerical results demonstrate the power of the neural network based adaptive critic method in solving this class of problems.
Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan
Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper develops a systematic scheme to solve for the optimal controls of variable time impulsive systems. First, the optimality conditions for variable time impulse driven systems are derived using the calculus of variation. After wards, a neural network based adaptive critic method is proposed to numerically solve the two-point boundary value problems formulated based on the optimality conditions derived. Finally, two examples - one linear and one nonlinear - are presented to illustrate the conditions derived and to show the power of the neural network based adaptive critic method proposed.
College Of Engineering Senior Design Competition Spring 2008, University Of Nevada, Las Vegas
College Of Engineering Senior Design Competition Spring 2008, University Of Nevada, Las Vegas
Fred and Harriet Cox Senior Design Competition Projects
Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.
The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …
Incorporation Of Evidences Into An Intelligent Computational Argumentation Network For A Web-Based Collaborative Engineering Design System, Xiaoqing Frank Liu, Ekta Khudkhudia, Ming-Chuan Leu
Incorporation Of Evidences Into An Intelligent Computational Argumentation Network For A Web-Based Collaborative Engineering Design System, Xiaoqing Frank Liu, Ekta Khudkhudia, Ming-Chuan Leu
Computer Science Faculty Research & Creative Works
Conflicts among the stakeholders are unavoidable in the process of collaborative engineering design. Resolution of these conflicts is a challenging task. In our previous research, a web based intelligent collaborative system was developed which provides decision-making support, using computational argumentation techniques. Enhancements were done to this system to incorporate the priorities of the stakeholders and to detect arguments that self conflict. As an effort to make this system more effective and more objective in the process of decision making, we develop a method to assess the effect of evidences in the argumentation network, using Dempster-Shafer theory of evidence and fuzzy …
Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne
Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Iterative learning control (ILC) is a learning technique used to improve the performance of systems that execute the same task multiple times. Learning transient behavior has emerged as an important topic in the design and analysis of ILC systems. In practice, the learning control is often low-pass filtered with a ldquoQ-filterrdquo to prevent transient growth, at the cost of performance. In this note, we consider linear time-invariant, discrete-time, single-input single-output systems, and convert frequency-domain uncertainty models to a time-domain representation for analysis. We then develop robust monotonic convergence conditions, which depend directly on the choice of the Q-filter and are …
Output Feedback Controller For Operation Of Spark Ignition Engines At Lean Conditions Using Neural Networks, Jonathan B. Vance, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Output Feedback Controller For Operation Of Spark Ignition Engines At Lean Conditions Using Neural Networks, Jonathan B. Vance, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Electrical and Computer Engineering Faculty Research & Creative Works
Spark ignition (SI) engines operating at very lean conditions demonstrate significant nonlinear behavior by exhibiting cycle-to-cycle bifurcation of heat release. Past literature suggests that operating an engine under such lean conditions can significantly reduce NO emissions by as much as 30% and improve fuel efficiency by as much as 5%-10%. At lean conditions, the heat release per engine cycle is not close to constant, as it is when these engines operate under stoichiometric conditions where the equivalence ratio is 1.0. A neural network controller employing output feedback has shown ability in simulation to reduce the nonlinear cyclic dispersion observed under …
Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins
Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins
Theses and Dissertations
The AFIT combustion optimization and analysis laser (COAL) lab is now completely operational and is state-of-the-art in combustion diagnostics. The objective of this research is to perform a validation of a laser diagnostic system and to begin the characterization of a small-scale model of an ultra-compact combustor (UCC). Validation of the laser system was accomplished by using planar laser induced fluorescence (PLIF) on a laminar premixed hydrogen-air flame produced by a Hencken burner. OH species concentrations are measured. Flame temperatures are determined with a two line fluorescence technique using different transitions in the (1,0) band of the OH (A-X) electronic …
Robust-Adaptive Magnetic Bearing Control Of Flexible Matrix Composite Rotorcraft Driveline, Hans August Desmidt, Kon-Well Wang, Edward Smith
Robust-Adaptive Magnetic Bearing Control Of Flexible Matrix Composite Rotorcraft Driveline, Hans August Desmidt, Kon-Well Wang, Edward Smith
Faculty Publications and Other Works -- Mechanical, Aerospace and Biomedical Engineering
Recent studies demonstrate that a key advantage of Flexible Matrix Composite (FMC) shaft technology is the ability to accommodate misalignments without need for segmenting or flexible couplings as required by conventional alloy and graphite/epoxy composite shafts. While this is indeed a very promising technology for rotorcraft driveshafts, the high damping loss-factor and thermal stiffness and damping sensitivities of the urethane matrix, makes FMC shafting more prone to self-heating and whirl instabilities. Furthermore, the relatively low bending stiffness and critical speeds of FMC shafts makes imbalance vibration a significant challenge to supercritical operation. To address these issues and advance the state-of-the-art, …
Photoelectric Charging By Ultraviolet Light Of A Lunar Dust Simulant In A Microgravity Environment, Microgravity Research Team 2008
Photoelectric Charging By Ultraviolet Light Of A Lunar Dust Simulant In A Microgravity Environment, Microgravity Research Team 2008
Reports and Proposals
No abstract provided.
The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Closed Reactor Experiments Using Equimolar N-Butane + Oxygen Premixtures At Reduced-Gravity, Howard Pearlman, Michael R. Foster
The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Closed Reactor Experiments Using Equimolar N-Butane + Oxygen Premixtures At Reduced-Gravity, Howard Pearlman, Michael R. Foster
Faculty Publications - Biomedical, Mechanical, and Civil Engineering
Experiments were conducted in a closed, spherical reactor aboard NASA's KC-135 reduced-gravity aircraft using an equimolar n-C4H10 + 0 2 premixture ( Le = 1.3) at subatmospheric · pressures to compliment model predictions and further explore the reactive-diffusive structure of cool flames and ignitions. The pressure and radial temperature histories were recorded and analyzed for different initial conditions. In addition, the visible light emission from excited formaldehyde was recorded using an intensified video camera and was observed to be radially symmetric in all cases. Unexpectedly, however, the measured temperature distributions during (and after the passage of) the cool flames and …
The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Numerical Simulations Using The Wang-Mou Mechanism, Howard Pearlman, Michael R. Foster
The Role Of Diffusive Transport On Low And Intermediate Temperature Hydrocarbon Oxidation: Numerical Simulations Using The Wang-Mou Mechanism, Howard Pearlman, Michael R. Foster
Faculty Publications - Biomedical, Mechanical, and Civil Engineering
The spatio-temporal temperature and species concentration distributions associated with low and intermediate temperature hydrocarbon oxidation are computed using a global thermo kinetic scheme augmented with diffusive transport. The scheme used for the computations was proposed by Wang and Mou and is extended to include diffusion of species and heat. The conservation equations for species and energy are then derived and solved for a one-dimensional and an axisymmetric, spherical domain for temperatures ranging from 540 to 660 Kat subatmospheric pressures. The predictions are then used to develop ignition diagrams for different Lewis ( Le) numbers. Increasing Le is found to promote …
Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt
Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Nanostructured membranes with precisely engineered nanopores were fabricated on a thin silicon nitride membrane, using a combination of bulk micromachining and focused-ion-beam drilling. These membranes are designed to preserve microscale blood channel dimensions, thereby permitting the red cell shape change that enhances gas exchange in the pulmonary capillary. The membranes were tested for their mechanical stability and the results were verified with finite element analysis. Initial studies have proven the membranes to be robust, and capable of withstanding pressures typically experienced in blood oxygenator channels. A novel MEMS-based blood oxygenation system employing the nanoporous membranes is also presented. The oxygenation …