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航空航天 & 军事 : 学术学位
One particular type of surface roughness that has become a critical area of research for aircraft designers is ice accretion. In this study, two problems that are encountered when modeling flow past aircraft icing are addressed: the geometric modeling of the ice shape and adequate resolution of the
The application of GPS carrier phase integer ambiguity resolution to low Earth orbit spacecraft missions has been a topic of great interest in recent years. This advanced processing technique may make it possible to achieve higher orbit accuracy for spacecraft that carry GPS receivers. The research
In the last few years a large number of potential future spacecraft projects have been identified which require spacecraft of unprecedented size, and hence unprecedented flexibility. The attitude control problems for such spacecraft are best characterized as simultaneous pointing control and shape c
AEROELASTIC STABILITY AND TIME RESPONSE ANALYSIS OF CONVENTIONAL AND SUPERCRITICAL AIRFOILS IN TRANSONIC FLOW BY TIME INTEGRATION METHOD.
Computer based numerical procedures have been developed for aero-elastic stability (flutter) and response analysis of conventional and supercritical airfoils in transonic flow by time integration method.; Airfoils are assumed to be oscillating in two dimensional, small disturbance and inviscid flows
This research discusses the application of the Direct Simulation Monte Carlo (DSMC) method to flows in Micro Electro Mechanical devices (MEMS) and the Space Shuttle leading edge reinforced Carbon-Carbon destruction due to the chemically active flows. For the MEMS device application an analysis to op
Scope and method of study. The purpose of this study was to determine the components of current aerospace collaborative efforts. There were 44 participants from two selected groups surveyed for this study. Nineteen were from the Oklahoma Air National Guard based in Oklahoma City representing the avi
A probabilistic multi-criteria decision making technique for conceptual and preliminary aerospace systems design.
It has always been the intention of systems engineering to invent or produce the best product possible. Many design techniques have been introduced over the course of decades that try to fulfill this intention. Unfortunately, no technique has succeeded in combining multi-criteria decision making wit
The aerodynamics characteristics of rotors in hover have been studied on stretched non-orthogonal grids using spatially high order symmetric total variation diminishing (STVD) schemes. Several companion numerical viscosity terms have been tested. The effects of higher order metrics, higher order loa
In aircraft structures and engines, fatigue damage is manifest in the progressive emergence of distributed surface cracks near locations of high stress concentrations. At the present time, reliable methods for prediction of fatigue crack initiation are not available, because the phenomenon starts at
The steady-state aerodynamic characteristics of three-dimensional waverider configurations immersed in hypersonic rarefied flows are investigated. Representative geometries are generated using an inverse design procedure, the method of osculating cones, which defines an exit plane shock shape and ap
Linear and nonlinear Kelvin-Helmholtz instabilities of high velocity magnetized shear layers with generalized polytrope laws.
The linear and nonlinear Kelvin-Helmholtz instability of tangential velocity discontinuities in high velocity magnetized plasmas with isotropic or anisotropic pressure is investigated. This problem is important in various geophysical, astrophysical and space configurations where there are spatially
A novel ground based test-bed for closed loop flight control of MAVs is developed. The emphasis is on easy re-programability, measurement of internal states of the vehicle, fail-safe features, and modular design so that control algorithms can be efficiently evaluated on a real MAV in flight. The sen
The role of nonlinearity in the generation and propagation of the noise radiated from high-performance jet aircraft is not a well understood phenomenon. To address this problem, an extensive experimental program has been carried out on high-speed model jets, including both flow-field and acoustic me
In this dissertation, we study the interaction between the control performance and the quality of the state estimation in a constrained Model Predictive Control (MPC) framework for systems with stochastic disturbances. This consists of three parts: (i) the development of a constrained MPC formulatio
In the competitive global market place, aerospace companies are forced to deliver the right products to the right market, with the right cost, and at the right time. However, the rapid development of technologies and new business opportunities, such as mergers, acquisitions, supply chain management,
Initially, tracking control of a fixed-base planar two-link rigid dynamics robot manipulator is simulated using inverse dynamics, linear quadratic regulator, fuzzy logic and linear quadratic Gaussian control strategies with a Jacobian transpose proportion-alderivative control law.; The inverse dynam
Optimal control and optimization of distributed parameter systems are discussed in the context of a common control framework. The adjoint method of optimization and the traditional linear quadratic regulator implementation of optimal control both employ adjoint or costate variables in the determinat
The flow physics of strained turbulent axial vortices has been studied using direct numerical simulations (DNS) as an investigative tool. These simulations use a b-spline/Fourier spectral method. Two specific cases have been considered. A vortex that has no axial flow in its initial laminar state is
In years past, aircraft conceptual design centered around creating a feasible aircraft that could be built and could fly the required missions. More recently, aircraft viability entered into conceptual design, allowing that the product's potential to be profitable should also be examined early in th
Spatially resolved sub-Doppler overtone gain measurements in a small scale supersonic hydrogen fluoride laser.
The overtone gain of a small-scale HF laser was measured using a sub-Doppler tunable diode laser system. Two-dimensional spatially resolved small signal gain and temperature maps were generated, which show a highly inhomogeneous gain medium indicating the dominant role that mixing of the fuel and ox