Recent research has produced a suite of powerful generic algorithms for identifying features on solid models, and after further refinement they are now capable of analysing the geometry of complex engineering components. In addition, a graphical user interface (GUI) has been developed for human-computer interaction. The main algorithm has also been embedded in a commercially available computer aided manufacturing (CAM) package which assists the manufacturing engineer in the production of NC code for machine-tools. A second application for the feature recognition engine is now being investigated, namely that of interaction with co-ordinate measuring machine (CMM) technology. Recent research has indicated that comparing a manufactured component (or batch of components) with a computer generated solid model gives a quick and highly accurate set of deviation data. Similarly, a solid model can be constructed from CMM probe data which represents the component tested. Identification of significant features within the solid model further assists the process by allowing the CMM operator to select areas of importance which have been suggested by the feature recognition system.
The Code for Extended Nonlinear Transient Analysis of Extraterrestrial Reactor Systems, CENTAR, is a simulation code for space nuclear reactors. This paper describes some of the individual components of this code and then combines them into a model of the TOPAZ system. Problems with the individual components and the system that is modeled are discussed. Unsatisfactory results are related to the lack of TOPAZ data and the beta version of the code utilized for this project.
The Air Force Institute of Technology (AFIT) has built a rotating prism chromotomographic hyperspectral imager (CTI)
with the goal of extending the technology to exploit spatially extended sources with quickly varying (> 10 Hz)
phenomenology, such as bomb detonations and muzzle flashes. This technology collects successive frames of 2-D data
dispersed at different angles multiplexing spatial and spectral information which can then be used to reconstruct any
arbitrary spectral plane(s). In this paper, the design of the AFIT instrument is described and then tested against a spectral
target with near point source spatial characteristics to measure spectral and spatial resolution. It will be shown that, in
theory, the spectral and spatial resolution in the 3-D spectral image cube is the nearly the same as a simple prism
spectrograph with the same design. However, error in the knowledge of the prism linear dispersion at the detector array
as a function of wavelength and projection angle will degrade resolution without further corrections. With minimal
correction for error and use of a simple shift-and-add reconstruction algorithm, the CTI is able to produce a spatial
resolution of about 2 mm in the object plane (234 μrad IFOV) and is limited by chromatic aberration. A spectral
resolution of less than 1nm at shorter wavelengths is shown, limited primarily by prism dispersion.
Infrared emissions from the detonation of three bomb types and four weights in a series of 56 events were recorded by a Fourier transform spectrometer in the midwave IR (1800-6000 wavenumbers) at temporal and spectral resolutions of 0.047 seconds and 16 wavenumbers, respectively. Fifteen time-resolved spectral datasets corresponding to two distinct chemical explosives were selected for this study. The detonation fireball intensities are well described as cooling greybodies, and a single Planckian distribution, modified by atmospheric absorption, has been fit to the spectra. Agreement between the model and data is within a few percent on average. However, the model underestimates the observed intensity by as much as 40% in the 2000-2200 wavenumber window and hot carbon dioxide at the surface of the fireball is a likely source of this spectral emission (spectral assignments have not yet been performed). For the statically detonated munitions, temperature curves are characterized by initial temperatures of 1685-1885 Kelvin and lifetimes of 0.91-1.24 seconds. Temperatures for some air delivered ordnance exhibited secondary maxima. Fireball areas are estimated without imagery. The model provides features which are reproducible within and characteristic of the munition type, providing promise for proposed event classification schemes. The timedependent Planckian fit residual near 2150 wavenumbers versus time provided the best discrimination between the two munition types, indicating that better understanding the non-Planckian behavior is key to the classification problem. A novel method to estimate the atmospheric transmittance function from the time-resolved fireball spectra is also developed.
The collisional dynamics of nonspherical aerosols is modeled by the introduction of a shape factor, β. Mechanistic calculation of β requires knowledge of the flow fields around the aerosols. Since actual aerosols can be complicated in shape and since the computation of flow fields can be quite difficult, insights into the nature of β are gained by using the superposition technique and studying aerosols that have tractable flow fields. The motion of an oblate spheroid in a viscous fluid is considered. The Navier-Stokes equations and associated boundary conditions are represented in oblate spheroidal coordinates. A combination of finite differences and spline-interpolation techniques is used to transform these equations to a form suitable for numerical computations. Converged results for the flow fields are obtained for a 0 to 5 range of Reynolds numbers. In the limit of zero Reynolds number, the results are found to be in agreement with the analytical solutions of Oberbeck.
This paper shows how to use a public domain raytracer POV-Ray (Persistence Of Vision Raytracer) to render multiand hyper-spectral scenes. The scripting environment allows automatic changing of the reflectance and transmittance parameters. The radiosity rendering mode allows accurate simulation of multiple-reflections between surfaces and also allows semi-transparent surfaces such as plant leaves. We show that POV-Ray computes occlusion accurately using a test scene with two blocks under a uniform sky. A complex scene representing a plant canopy is generated using a few lines of script. With appropriate rendering settings, shadows cast by leaves are rendered in many bands. Comparing single and multiple reflection renderings, the effect of multiple reflections is clearly visible and accounts for 25% of the overall apparent canopy reflectance in the near infrared.
This research highlights the results obtained from applying the method of inverse kinematics, using Groebner basis theory, to the human gait cycle to extract and identify lower extremity gait signatures. The increased threat from suicide bombers and the force protection issues of today have motivated a team at Air Force Institute of Technology (AFIT) to research pattern recognition in the human gait cycle. The purpose of this research is to identify gait signatures of human subjects and distinguish between subjects carrying a load to those subjects without a load. These signatures were investigated via a model of the lower extremities based on motion capture observations, in particular, foot placement and the joint angles for subjects affected by carrying extra load on the body. The human gait cycle was captured and analyzed using a developed toolkit consisting of an inverse kinematic motion model of the lower extremity and a graphical user interface. Hip, knee, and ankle angles were analyzed to identify gait angle variance and range of motion. Female subjects exhibited the most knee angle variance and produced a proportional correlation between knee flexion and load carriage.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)