NEW ULTRA-LIGHTWEIGHT STIFF PANELS FOR SPACE APERTURES

Stiff, ultra-lightweight thermal-formed polyimide panels considered in this dissertation are examples of next generation gossamer structures that resolve some of the technology barriers of previous, membrane-dominated gossamer designs while maintaining their low mass and low stowage volume characteristics. The research involved statically and dynamically characterizing and modeling several of these panels to develop validated computer models which can be used to determine the effects of changing manufacturing parameters and scalability. Static characterization showed substantial local nonlinear behavior that was replicated by new physics-based finite element models, and global linear bending behavior that was modeled using classical shell finite elements incorporating effective properties in place of bulk material properties to represent the unique stiffening structure of these panels. Dynamic characterization was performed on individual panels using standard impact hammer and accelerometer testing, enabling successful extraction of several structural natural frequencies and mode shapes. Additionally, the three dimensional time history of the surface of the panels was rendered from video data, and temporal filters were applied to the data to examine the frequency content. These data were also correlated to the shell element numerical models. Overall, the research contributes to the total knowledge base of gossamer technologies, advances stiff panel-based structures toward space qualification, and demonstrates their potential for use in apertures and other spacecraft

A Taskable Space Vehicle: Realizing Cost Savings by Combining Orbital and Suborbital Flight

The use of space gives the United States distinct advantages in any battlefield environment, but the high cost of space operations increasingly jeopardizes those advantages. Although the United States pioneered much of the current space technology, declining budgets for space research, development, and operations leave our legacy systems vulnerable to adversaries around the world. Other nations formerly incapable of space exploitation are quickly learning to counter US space technologies at surprisingly low costs. In order to reduce the expense of deploying and maintaining a robust space capability, the Department of Defense (DOD) must change the status quo in space operations or risk losing its dominance

Optical Flow Background Estimation for Real-time Pan/tilt Camera Object Tracking

As Computer Vision (CV) techniques develop, pan/tilt camera systems are able to enhance data capture capabilities over static camera systems. In order for these systems to be effective for metrology purposes, they will need to respond to the test article in real-time with a minimum of additional uncertainty. A methodology is presented here for obtaining high-resolution, high frame-rate images, of objects traveling at speeds ⩾1.2 m/s at 1 m from the camera by tracking the moving texture of an object. Strong corners are determined and used as flow points using implementations on a graphic processing unit (GPU), resulting in significant speed-up over central processing units (CPU). Based on directed pan/tilt motion, a pixel-to-pixel relationship is used to estimate whether optical flow points fit background motion, dynamic motion or noise. To smooth variation, a two-dimensional position and velocity vector is used with a Kalman filter to predict the next required position of the camera so the object stays centered in the image. High resolution images can be stored by a parallel process resulting in a high frame rate procession of images for post-processing. The results provide real-time tracking on a portable system using a pan/tilt unit for generic moving targets where no training is required and camera motion is observed from high accuracy encoders opposed to image correlation

The effects of β-alanine supplementation on muscle pH and the power-duration relationship during high-intensity exercise

Purpose: To investigate the influence of β-alanine (BA) supplementation on muscle carnosine content, muscle pH and the power-duration relationship (i.e., critical power and W′). Methods: In a double-blind, randomized, placebo-controlled study, 20 recreationally-active males (22 ± 3 y, VO˙2peak 3.73 ± 0.44 L·min−1) ingested either BA (6.4 g/d for 28 d) or placebo (PL) (6.4 g/d) for 28 d. Subjects completed an incremental test and two 3-min all-out tests separated by 1-min on a cycle ergometer pre- and post-supplementation. Muscle pH was assessed using 31P-magnetic resonance spectroscopy (MRS) during incremental (INC KEE) and intermittent knee-extension exercise (INT KEE). Muscle carnosine content was determined using 1H-MRS. Results: There were no differences in the change in muscle carnosine content from pre- to post-intervention (PL: 1 ± 16% vs. BA: −4 ± 25%) or in muscle pH during INC KEE or INT KEE (P > 0.05) between PL and BA, but blood pH (PL: −0.06 ± 0.10 vs. BA: 0.09 ± 0.13) during the incremental test was elevated post-supplementation in the BA group only (P < 0.05). The changes from pre- to post-supplementation in critical power (PL: −8 ± 18 W vs. BA: −6 ± 17 W) and W′ (PL: 1.8 ± 3.3 kJ vs. BA: 1.5 ± 1.7 kJ) were not different between groups. No relationships were detected between muscle carnosine content and indices of exercise performance. Conclusions: BA supplementation had no significant effect on muscle carnosine content and no influence on intramuscular pH during incremental or high-intensity intermittent knee-extension exercise. The small increase in blood pH following BA supplementation was not sufficient to significantly alter the power-duration relationship or exercise performance

Phage Orf family recombinases:conservation of activities and involvement of the central channel in DNA binding

Genetic and biochemical evidence suggests that λ Orf is a recombination mediator, promoting nucleation of either bacterial RecA or phage Redβ recombinases onto single-stranded DNA (ssDNA) bound by SSB protein. We have identified a diverse family of Orf proteins that includes representatives implicated in DNA base flipping and those fused to an HNH endonuclease domain. To confirm a functional relationship with the Orf family, a distantly-related homolog, YbcN, from Escherichia coli cryptic prophage DLP12 was purified and characterized. As with its λ relative, YbcN showed a preference for binding ssDNA over duplex. Neither Orf nor YbcN displayed a significant preference for duplex DNA containing mismatches or 1-3 nucleotide bulges. YbcN also bound E. coli SSB, although unlike Orf, it failed to associate with an SSB mutant lacking the flexible C-terminal tail involved in coordinating heterologous protein-protein interactions. Residues conserved in the Orf family that flank the central cavity in the λ Orf crystal structure were targeted for mutagenesis to help determine the mode of DNA binding. Several of these mutant proteins showed significant defects in DNA binding consistent with the central aperture being important for substrate recognition. The widespread conservation of Orf-like proteins highlights the importance of targeting SSB coated ssDNA during lambdoid phage recombination

Can precursors improve the transmission of energy at optical frequencies?

The recent interest in precursors has been fuelled by the possibility of using them for the efficient transmission of information through absorbing media at radio or optical frequencies. Here we demonstrate that the low attenuation experienced by the Brillouin precursor is attributed to the inherently low absorption of dispersive media near DC, a characteristic already exploited with communications systems using the extremely low frequency (ELF) band. Pulses, regardless of their temporal width and carrier frequency, always obey Beer's law as long as they propagate in the linear time invariant regime. We conclude with an FDTD simulation of the Maxwell–Bloch equations that shows how optical coherent bleaching effects, which take place in the linear time variant regime of the Lorentz oscillator model, can cause sustained deviations from Beer's law over relatively long distances of water

Status of Muon Collider Research and Development and Future Plans

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam