Search Tree Pruning for Progressive Neural Architecture Search

Our neural architecture search algorithm progressively searches a tree of neural network architectures. Child nodes are created by inserting new layers determined by a transition graph into a parent network up to a maximum depth and pruned when performance is worse than its parent. This increases efficiency but makes the algorithm greedy. Simpler networks are successfully found before more complex ones that can achieve benchmark performance similar to other top-performing networks

Liquid Oxygen/Liquid Methane Integrated Propulsion System Test Bed

In support of NASA?s Propulsion and Cryogenic Advanced Development (PCAD) project, a liquid oxygen (LO2)/liquid methane (LCH4) Integrated Propulsion System Test Bed (IPSTB) was designed and advanced to the Critical Design Review (CDR) stage at the Johnson Space Center. The IPSTB?s primary objectives are to study LO2/LCH4 propulsion system steady state and transient performance, operational characteristics and to validate fluid and thermal models of a LO2/LCH4 propulsion system for use in future flight design work. Two phase thermal and dynamic fluid flow models of the IPSTB were built to predict the system performance characteristics under a variety of operating modes and to aid in the overall system design work. While at ambient temperature and simulated altitude conditions at the White Sands Test Facility, the IPSTB and its approximately 600 channels of system instrumentation would be operated to perform a variety of integrated main engine and reaction control engine hot fire tests. The pressure, temperature, and flow rate data collected during this testing would then be used to validate the analytical models of the IPSTB?s thermal and dynamic fluid flow performance. An overview of the IPSTB design and analytical model development will be presented

3-Faceted Array With Low Side Lobe Levels Using Tunable Windows

In this paper, a 3-faceted phased array antenna synthesised for low side lobe levels using a tuneable window is presented. The array consists of eight left hand circularly polarised antennas. The phase difference of the antennas on the faceted structure is first compensated for and then an amplitude tapering method is used to synthesise the array to have a low sidelobe level, (SLL). The effect of the phase compensation on the angular scanning range of the 3-faceted array is then investigated. Simulation results show that the radiation patterns generated with tuneable windows, such as Kaiser, Chebyshev and Taylor, have a similar profile to the uniform amplitude distribution but with a much lower SLL and broader main beam. This technique enables the faceted structure to be synthesised for low SLL and at the same time retain its radiation pattern profile

Electrical and optical properties of vanadium tellurite glasses

Glasses in the system v₂o₅-Te0₂ were prepared at intervals throughout the glass-forming composition range. The vanadium valence state was varied for each composition by the addition of elemental tellurium to reduce the melt. A chemical analysis method was devised to determine the v⁴⁺:vtotal ratio. Conductivity and thermopower measurements were made as functions of composition, valence ratio and temperature. The conductivity was found to increase as the total vanadium content increased and to be 21/2 to 3 orders of magnitude greater than that of a v₂0₅-P₂0₅ glass of similar v₂o₅ content. A maximum in conductivity was observed as the vanadium valence ratio was varied. This maximum was shifted to values around v⁴⁺:vtotal = 0.2 from the theoretically predicted value of 0.5. At temperatures above 250 K the conductivity varied exponentially with temperature with activation energies in the range 0.25 to 0.40 eV. Below this temperature there was a continuous decrease in slope of the conductivity down to the lowest temperature at which measurements were made. Thermopower was found to be negative and temperature independent above 250 K, while below this temperature it decreased in an activated manner with an activation energy of 0.02 eV. As a function of valence ratio the thermopower followed the behaviour predicted by Heikes and Ure, with the exception that the change of sign occurred at v⁴⁺:vtot ratios of around 0.2, instead of the theoretically predicted value of 0.5. (iii) Measurements were made of the optical absorption coefficient as functions of photon energy, composition, valence ratio and temperature. Temperature and composition did not affect the absorption spectrum significantly except that an absorption band appeared below the fundamental absorption edge as the glasses were reduced. The high electric field and a.c. properties of the glasses were also measured. These are consistent with hopping conduction of carriers between v⁴⁺ and v⁵⁺ sites. This data gives indirect indications of an inhomogeneous glass structure

Recent Transits of the Super-Earth Exoplanet GJ 1214b

We report recent ground-based photometry of the transiting super-Earth exoplanet GJ1214b at several wavelengths, including the infrared near 1.25 microns (J-band). We observed a J-band transit with the FLAMINGOS infrared imager and the 2.1-meter telescope on Kitt Peak, and we observed several optical transits using a 0.5-meter telescope on Kitt Peak and the 0.36-meter Universidad de Monterrey Observatory telescope. Our high-precision J-band observations exploit the brightness of the M-dwarf host star at this infrared wavelength as compared to the optical, as well as being significantly less affected by stellar activity and limb darkening. We fit the J-band transit to obtain an independent determination of the planetary and stellar radii. Our radius for the planet (2.61^+0.30_-0.11 Earth radii) is in excellent agreement with the discovery value reported by Charbonneau et al. based on optical data. We demonstrate that the planetary radius is insensitive to degeneracies in the fitting process. We use all of our observations to improve the transit ephemeris, finding P=1.5804043 +/- 0.0000005 days, and T0=2454964.94390 +/- 0.00006 BJD.Comment: Accepted for ApJ Letters, 7 pages, 3 Figures, 2 Table

The DELTA MONSTER: An RPV designed to investigate the aerodynamics of a delta wing platform

The mission requirements for the performance of aerodynamic tests on a delta wind planform posed some problems, these include aerodynamic interference; structural support; data acquisition and transmission instrumentation; aircraft stability and control; and propulsion implementation. To eliminate the problems of wall interference, free stream turbulence, and the difficulty of achieving dynamic similarity between the test and actual flight aircraft that are associated with aerodynamic testing in wind tunnels, the concept of the remotely piloted vehicle which can perform a basic aerodynamic study on a delta wing was the main objective for the Green Mission - the Delta Monster. The basic aerodynamic studies were performed on a delta wing with a sweep angle greater than 45 degrees. These tests were performed at various angles of attack and Reynolds numbers. The delta wing was instrumented to determine the primary leading edge vortex formation and location, using pressure measurements and/or flow visualization. A data acquisition system was provided to collect all necessary data