Space shuttle main engine: Interactive design challenges

The operating requirements established by NASA for the SSME were considerably more demanding than those for earlier rocket engines used in the military launch vehicles or Apollo program. The SSME, in order to achieve the high performance, low weight, long life, reusable objectives, embodied technical demands far in excess of its predecessor rocket engines. The requirements dictated the use of high combustion pressure and the staged combustion cycle which maximizes performance through total use of all propellants in the main combustion process. This approach presented a myriad of technical challenges for maximization of performance within attainable state of the art capabilities for operating pressures, operating temperatures and rotating machinery efficiencies. Controlling uniformity of the high pressure turbomachinery turbine temperature environment was a key challenge for thrust level and life capability demanding innovative engineering. New approaches in the design of the components were necessary to accommodate the multiple use, minimum maintenance objectives. Included were the use of line replaceable units to facilitate field maintenance automatic checkout and internal inspection capabilities

Robot-Mediated Interviews with Children : What do potential users think?

Luke Wood, Hagen Lehmann, Kerstin Dautenhahn, Ben Robins, Austen Rayner, and Dag Syrdal, ‘Robot-Mediated Interviews with Children: What do potential users think?’, paper presented at the 50th Annual Convention of the Society for the Study of Artificial Intelligence and the Simulation of Behaviour, 1 April 2014 – 4 April 2014, London, UK.When police officers are conducting interviews with children, some of the disclosures can be quite shocking. This can make it difficult for an officer to maintain their composure without subtly indicating their shock to the child, which can in turn impede the information acquisition process. Using a robotic interviewer could eliminate this problem as the behaviours and expressions of the robot can be consciously controlled. To date research investigating the potential of Robot-Mediated Interviews has focused on establishing whether children will respond to robots in an interview scenario and if so how well. The results of these studies indicate that children will talk to a robot in an interview scenario in a similar way to which they talk to a human interviewer. However, in order to test if this approach would work in a real world setting, it is important to establish what the experts (e.g. specialist child interviewers) would require from the system. To determine the needs of the users we conducted a user panel with a group of potential real world users to gather their views of our current system and find out what they would require for the system to be useful to them. The user group we worked with consisted of specialist child protection police officers based in the UK. The findings from this panel suggest that a Robot-Mediated Interviewing system would need to be more flexible than our current system in order to respond to unpredictable situations and paths of investigation. This paper gives an insight into what real world users would need from a Robot-Mediated Interviewing system

A DC magnetic metamaterial

Electromagnetic metamaterials are a class of materials which have been artificially structured on a subwavelength scale. They are currently the focus of a great deal of interest because they allow access to previously unrealisable properties like a negative refractive index. Most metamaterial designs have so far been based on resonant elements, like split rings, and research has concentrated on microwave frequencies and above. In this work, we present the first experimental realisation of a non-resonant metamaterial designed to operate at zero frequency. Our samples are based on a recently-proposed template for an anisotropic magnetic metamaterial consisting of an array of superconducting plates. Magnetometry experiments show a strong, adjustable diamagnetic response when a field is applied perpendicular to the plates. We have calculated the corresponding effective permeability, which agrees well with theoretical predictions. Applications for this metamaterial may include non-intrusive screening of weak DC magnetic fields.Comment: 6 pages, 3 figure

3-D Models of Embedded High-Mass Stars: Effects of a Clumpy Circumstellar Medium

We use 3-D radiative transfer models to show the effects of clumpy circumstellar material on the observed infrared colors of high mass stars embedded in molecular clouds. We highlight differences between 3-D clumpy and 1-D smooth models which can affect the interpretation of data. We discuss several important properties of the emergent spectral energy distribution (SED): More near-infrared light (scattered and direct from the central source) can escape than in smooth 1-D models. The near- and mid-infrared SED of the same object can vary significantly with viewing angle, depending on the clump geometry along the sightline. Even the wavelength-integrated flux can vary with angle by more than a factor of two. Objects with the same average circumstellar dust distribution can have very different near-and mid-IR SEDs depending on the clump geometry and the proximity of the most massive clump to the central source. Although clumpiness can cause similar objects to have very different SEDs, there are some observable trends. Near- and mid-infrared colors are sensitive to the weighted average distance of clumps from the central source and to the magnitude of clumpy density variations (smooth-to-clumpy ratio). Far-infrared emission remains a robust measure of the total dust mass. We present simulated SEDs, colors, and images for 2MASS and Spitzer filters. We compare to observations of some UCHII regions and find that 3-D clumpy models fit better than smooth models. In particular, clumpy models with fractal dimensions in the range 2.3-2.8, smooth to clumpy ratios of <50%, and density distributions with shallow average radial density profiles fit the SEDs best.Comment: accepted to ApJ; version with full-res figures: http://www.astro.virginia.edu/~ri3e/clumpy3d.pd

High spectral resolution time-resolved optical spectroscopy of V893 Sco

We present high resolution time-resolved optical spectra of the high inclination short orbital period dwarf nova V893 Sco. We performed spectral analysis through radial velocity measurements, Doppler mapping, and ratioed Doppler maps. Our results indicate that V893 Sco's accretion disk is dissimilar to WZ Sge's accretion disk, and does not fit any of the current accretion disk models. We derive the system parameters M1 and i, and present evidence for V893 Sco as a very young cataclysmic variable and an ER UMa star. We advance the hypothesis that all ER UMa stars may be newly formed cataclysmic variables.Comment: 23 pages (total), 8 figures, accepted by Ap

Numerical Evidence for Divergent Burnett Coefficients

In previous papers [Phys. Rev. A {\bf 41}, 4501 (1990), Phys. Rev. E {\bf 18}, 3178 (1993)], simple equilibrium expressions were obtained for nonlinear Burnett coefficients. A preliminary calculation of a 32 particle Lennard-Jones fluid was presented in the previous paper. Now, sufficient resources have become available to address the question of whether nonlinear Burnett coefficients are finite for soft spheres. The hard sphere case is known to have infinite nonlinear Burnett coefficients (ie a nonanalytic constitutive relation) from mode coupling theory. This paper reports a molecular dynamics caclulation of the third order nonlinear Burnett coefficient of a Lennard-Jones fluid undergoing colour flow, which indicates that this term is diverges in the thermodynamic limit.Comment: 12 pages, 9 figure

Anisotropic charge transport in non-polar GaN QW: polarization induced charge and interface roughness scattering

Charge transport in GaN quantum well (QW) devices grown in non-polar direction has been theoretically investigated . Emergence of anisotropic line charge scattering mechanism originating as a result of anisotropic rough surface morphology in conjunction with in-plane built-in polarization has been proposed. It has shown that in-plane growth anisotropy leads to large anisotropic carrier transport at low temperatures. At high temperatures, this anisotropy in charge transport is partially washed out by strong isotropic optical phonon scattering in GaN QW.Comment: 4 pages, 4 figure