Preliminary design study of a quiet, high flow fan (QHF) stage

Concepts selected to reduce fan generated noise in a turbofan are presented. Near-sonic flow at the fan inlet to reduce upstream propagated noise and the use of long-chord vanes to reduce downstream noise is discussed. The near-sonic condition at the rotor inlet plane was achieved by designing for high specific mass flow and by maintaining the high flow at reduced power by variable stators and variable fan exhaust nozzle. The long-chord vanes reduce response to unsteady flow. The acoustic design showed that long-chord stators would significantly reduce turbofan source noise and that other stator design parameters have no appreciable effect on noise for the spacing and chord length of the turbofan design. Four rig flow paths studied in the aerodynamic preliminary design are discussed. Noise prediction results indicate that a turbofan powered aircraft would be under federal air regulations levels without any acoustic treatment

Exploring the Spatial Density of Strategy Models in a Realistic Distributed Interactive Application

As Distributed Interactive Applications (DIAs) become increasingly more prominent in the video game industry they must scale to accommodate progressively more users and maintain a globally consistent worldview. However, network constraints, such as bandwidth, limit the amount of communication allowed between users. Several methods of reducing network communication packets, while maintaining consistency, exist. These include dead reckoning and the hybrid strategy-based modelling approach. This latter method combines a short-term model such as dead reckoning with a long-term strategy model of user behaviour. By employing the strategy that most closely represents user behaviour, a reduction in the number of network packets that must be transmitted to maintain consistency has been shown. In this paper a novel method for constructing multiple long-term strategies using dead reckoning and polygons is described. Furthermore the algorithms are implemented in an industry-proven game engine known as Torque. A series of experiments are executed to investigate the effects of varying the spatial density of strategy models on the number of packets that need to be transmitted to maintain the global consistency of the DIA. The results show that increasing the spatial density of strategy models allows a higher consistency to be achieved with fewer packets using the hybrid strategy-based model than with pure dead reckoning. In some cases, the hybrid strategy-based model completely replaces dead reckoning as a means of communicating updates

Exploring the Spatial Density of Strategy Models in a Realistic Distributed Interactive Application

As Distributed Interactive Applications (DIAs) become increasingly more prominent in the video game industry they must scale to accommodate progressively more users and maintain a globally consistent worldview. However, network constraints, such as bandwidth, limit the amount of communication allowed between users. Several methods of reducing network communication packets, while maintaining consistency, exist. These include dead reckoning and the hybrid strategy-based modelling approach. This latter method combines a short-term model such as dead reckoning with a long-term strategy model of user behaviour. By employing the strategy that most closely represents user behaviour, a reduction in the number of network packets that must be transmitted to maintain consistency has been shown. In this paper a novel method for constructing multiple long-term strategies using dead reckoning and polygons is described. Furthermore the algorithms are implemented in an industry-proven game engine known as Torque. A series of experiments are executed to investigate the effects of varying the spatial density of strategy models on the number of packets that need to be transmitted to maintain the global consistency of the DIA. The results show that increasing the spatial density of strategy models allows a higher consistency to be achieved with fewer packets using the hybrid strategy-based model than with pure dead reckoning. In some cases, the hybrid strategy-based model completely replaces dead reckoning as a means of communicating updates

Representing Random Terrain on Resource Limited Devices

Random terrain generation is the procedural creation of a set of data that represents closely a believable landscape. Common techniques of achieving this include the use of fractals and noise. Such techniques usually require a large volume of memory, as the geometry of the terrain needs to be calculated and stored at run time. Given the limited memory available on mobile devices, such as mobile telephones, the storage of the data required to represent massive terrains can be difficult. In this paper, we propose a novel method of storing terrain data on devices with limited memory. This method involves placing pre-computed blocks of terrain, known as terrain tiles, together in a psuedo-random manner as governed by a noise function known as Perlin noise. This allows large amounts of terrain data to be represented while still giving the appearance of a randomly generated terrain. Traditionally, Perlin noise is used in the procedural generation of textures and the modeling of naturally occurring phenomena. Using Perlin noise, only a subset of the overall data generated by the function needs to be stored at any one time. The approach outlined in this paper associates a tile of terrain with each value generated by the Perlin Noise function, meaning that only a subsection of the total terrain is stored in memory at any one time. We show how this process can be executed in real time on a resource limited device known as the Game Boy Advance, and also illustrate a significant reduction in the memory requirements of terrain storage when compared with traditional methods

The Three-Dimensional Structure of Cassiopeia A

We used the Spitzer Space Telescope's Infrared Spectrograph to map nearly the entire extent of Cassiopeia A between 5-40 micron. Using infrared and Chandra X-ray Doppler velocity measurements, along with the locations of optical ejecta beyond the forward shock, we constructed a 3-D model of the remnant. The structure of Cas A can be characterized into a spherical component, a tilted thick disk, and multiple ejecta jets/pistons and optical fast-moving knots all populating the thick disk plane. The Bright Ring in Cas A identifies the intersection between the thick plane/pistons and a roughly spherical reverse shock. The ejecta pistons indicate a radial velocity gradient in the explosion. Some ejecta pistons are bipolar with oppositely-directed flows about the expansion center while some ejecta pistons show no such symmetry. Some ejecta pistons appear to maintain the integrity of the nuclear burning layers while others appear to have punched through the outer layers. The ejecta pistons indicate a radial velocity gradient in the explosion. In 3-D, the Fe jet in the southeast occupies a "hole" in the Si-group emission and does not represent "overturning", as previously thought. Although interaction with the circumstellar medium affects the detailed appearance of the remnant and may affect the visibility of the southeast Fe jet, the bulk of the symmetries and asymmetries in Cas A are intrinsic to the explosion.Comment: Accepted to ApJ. 54 pages, 21 figures. For high resolution figures and associated mpeg movie and 3D PDF files, see http://homepages.spa.umn.edu/~tdelaney/pape

Temperature-Dependent Magnetoelectric Effect from First Principles

We show that nonrelativistic exchange interactions and spin fluctuations can give rise to a linear magnetoelectric effect in collinear antiferromagnets at elevated temperatures that can exceed relativistic magnetoelectric responses by more than 1 order of magnitude. We show how symmetry arguments, ab initio methods, and Monte Carlo simulations can be combined to calculate temperature-dependent magnetoelectric susceptibilities entirely from first principles. The application of our method to Cr2O3 gives quantitative agreement with experiment.

Multiple Gluon Effects in q+qˉ→t+tˉ+Xq+\bar q\to t+\bar t + X at FNAL Energies: Semi-Analytical Results

We apply our Yennie-Frautschi-Suura exponentiated cross section formulas for the parton processes q + {^(} \bar q {^)}{^\prime} \ra q{^\prime}{^\prime} + {^(} \bar q {^)}{^\prime}{^\prime}{^\prime} + n(G) to the process q + \bar q \ra t + \bar t + n(G) at FNAL energies, where G is a QCD gluon. We use semi-analytical methods to compute the ratio $r_{exp}=\sigma_{exp}/\sigma_B$, where $\sigma_{exp}$ is our soft gluon YFS exponentiated cross section and $\sigma_B$ is the Born cross section. For $m_t= 0.176(0.199)$TeV, we get $r_{exp}=1.65(1.48)$, respectively, for $q=u$ for example. These results are not inconsistent with the recent observations by CDF and D0.Comment: 6 pages, latex replaces postscript at archiver's reques

Task 7: ADPAC User's Manual

The overall objective of this study was to develop a 3-D numerical analysis for compressor casing treatment flowfields. The current version of the computer code resulting from this study is referred to as ADPAC (Advanced Ducted Propfan Analysis Codes-Version 7). This report is intended to serve as a computer program user's manual for the ADPAC code developed under Tasks 6 and 7 of the NASA Contract. The ADPAC program is based on a flexible multiple- block grid discretization scheme permitting coupled 2-D/3-D mesh block solutions with application to a wide variety of geometries. Aerodynamic calculations are based on a four-stage Runge-Kutta time-marching finite volume solution technique with added numerical dissipation. Steady flow predictions are accelerated by a multigrid procedure. An iterative implicit algorithm is available for rapid time-dependent flow calculations, and an advanced two equation turbulence model is incorporated to predict complex turbulent flows. The consolidated code generated during this study is capable of executing in either a serial or parallel computing mode from a single source code. Numerous examples are given in the form of test cases to demonstrate the utility of this approach for predicting the aerodynamics of modem turbomachinery configurations