US Air Force Test Research Articles

Boeing and US Air Force test microwave missile

Boeing and US Air Force test microwave missile

Benchmarking Quickpalm and Other Molecule Localization Software for Super-Resolution Microscopy

Image processing software is used to estimate the positions of fluorescent molecules in super-resolution microscopy images. The rejection methods (for distinguishing single-molecule and multi-molecule images) and fitting algorithms (for estimating molecular positions) used determine the quality and reliability of the reconstructed images. We benchmarked and analyzed the ImageJ plug-in called QuickPALM. To do this, we used simulations of two-molecule images (with realistic point spread functions and Poisson noise model) as input. These images were generated with known molecule positions, to test the predictions of QuickPALM against the actual images. Our analysis showed that the accuracy dropped significantly when molecules were less than one wavelength apart, as there was rejection of multiple molecules in close proximity. With our results, we were also able to show that localization bias occurred towards the center of each pixel, distorting the overall image. The result was confirmed by simulating a PALM experiment on the US Air Force Test Pattern. We also wrote our own molecule localization plug-in (for ImageJ) utilizing second-moments (as a rejection criterion) and a fast maximum likelihood estimator (for estimating molecular positions), to compare with QuickPALM. We were able to show that the new plug-in had improved precision and accuracy when using the same single-molecule and two-molecule images. We also showed that the maximum likelihood estimator had no bias towards the center of each pixel when processing the US Air Force Test Pattern.

Pixelation effect removal from fiber bundle probe based optical coherence tomography imaging

A method of eliminating pixelization effect from en face optical coherence tomography (OCT) image when a fiber bundle is used as an OCT imaging probe is presented. We have demonstrated that applying a histogram equalization process before performing a weighted-averaged Gaussian smoothing filter to the original lower gray level intensity based image not only removes the structural artifact of the bundle but also enhances the image quality with minimum blurring of object’s image features. The measured contrast-to-noise ratio (CNR) for an image of the US Air Force test target was 14.7dB (4.9dB), after (before) image processing. In addition, by performing the spatial frequency analysis based on two-dimensional discrete Fourier transform (2-D DFT), we were able to observe that the periodic intensity peaks induced by the regularly arrayed structure of the fiber bundle can be efficiently suppressed by 41.0dB for the first nearby side lobe as well as to obtain the precise physical spacing information of the fiber grid. The proposed combined method can also be used as a straight forward image processing tool for any imaging system utilizing fiber bundle as a high-resolution imager.

A Flight Test Evaluation of the Arc Segment Attitude Reference for Use as a Primary Flight Reference in Helmet-Mounted Displays

The objective of this evaluation was to determine if the use of the Arc Segment Attitude Reference (ASAR) symbology in a head-up display (HUD) in place of the legacy climb-dive ladder attitude reference aids in unusual attitude recovery (UAR) piloting tasks as specified in AFM 11–217 for use as a primary flight reference (PFR). Flight tests were conducted at the US Air Force Test Pilot School (TPS), Edwards AFB, California on the NF-16D Variable-stability In-flight Simulator Test Aircraft (VISTA). Five VISTA flight UAR test sorties were flown. The time for the pilot to initiate a recovery was measured in addition to the correctness of the recovery. The flight tests were conducted with the use of the HUD combiner on VISTA to examine three symbology configurations. Each of the symbology configurations, the Mil-Std-1787C HUD, dual-articulated (DA) HUD, and ASAR HUD were evaluated by five pilots for the UAR task. The flight test results revealed the ASAR resulted in faster stick input for correction of UARs then the Mil-Std-1787C HUD. This study along with other supporting research indicates that the configural design properties of the ASAR support the ability of pilots to quickly ascertain aircraft attitude.

Material characterization and development of a constitutive relationship for hypervelocity impact of 1080 Steel and VascoMax 300

The area of hypervelocity impact and associated high energy is one of extreme interest in the research community. A specific example of this emphasis is the US Air Force test facility at Holloman Air Force Base which specializes in the field of hypervelocity impact testing. This Holloman AFB High Speed Test Track (HHSTT) is currently working to increase the speed of their test vehicle to above Mach 10. As the test sled's speed has increased into the Mach 8.5 range, a material interaction has developed which causes “gouging” in the rails or the sled's “shoes” and this starts a process that can result in catastrophic failure. In the tests that do not structurally fail, the rails and shoes are damaged. Previous efforts in investigating this event have resulted in a choice of the most suitable computer code (CTH), and a model of the shoe/rail interaction. However, the specific materials present in this impact problem were not available in CTH. In this work, the specific materials present at the HHSTT (VascoMax 300 and 1080 Steel) will be characterized using the Split Hopkinson Bar Test and a Johnson–Cook constitutive model will be developed. The model will then be validated by comparison to a series of Taylor impact tests. The coating materials utilized on the rails at the HHSTT will also be evaluated using a Taylor impact test.

A method for single-pass distortion correction using holography in rhodium-doped barium titanate

We present a holographic method of one-way image transmission with ‘real-time’ correction of distortion through an optical system. The technique is demonstrated using a crystal of photorefractive rhodium-doped barium titanate as the holographic medium and corrects for phase distortions imposed upon a US Air Force test chart. This technique is suitable for applications in both cw and pulsed regimes, and for either fixed or changing distortions.

Status of the Air Force nickel hydrogen low earth orbit life test

The US Air Force NiH/sub 2/ LEO (low earth orbit) life test consists of 200 cells undergoing real-time LEO cycling, pulse discharge testing, and storage testing. To date, three of the program's four objectives have been met: NiH/sub 2/ performance in LEO applications has been demonstrated. A significant number of cells have completed more than 20,000 cycles at 40% DOD. A database for cells of both 3.5 in. and 4.5 in. diameter has been generated. There have been no indications of any performance problems related to scaling up in terms of cell size. Initial data on the pulse discharge performance of a small number of cells has been demonstrated. Concerning the goal of achieving 20,000 cycles at 60% DOD, the data are mixed. Overall, it appears highly unlikely that cell designs such as those currently in the US Air Force test can achieve 20,000 cycles at 60%. >