13,595 research outputs found
A system for aerodynamic design and analysis of supersonic aircraft. Part 1: General description and theoretical development
An integrated system of computer programs was developed for the design and analysis of supersonic configurations. The system uses linearized theory methods for the calculation of surface pressures and supersonic area rule concepts in combination with linearized theory for calculation of aerodynamic force coefficients
A computational system for aerodynamic design and analysis of supersonic aircraft. Part 1: General description and theoretical development
An integrated system of computer programs was developed for the design and analysis of supersonic configurations. The system uses linearized theory methods for the calculation of surface pressures and supersonic area rule concepts in combination with linearized theory for calculation of aerodynamic force coefficients. Interactive graphics are optional at the user's request. Schematics of the program structure and the individual overlays and subroutines are described
A compilation and analysis of typical approach and landing data for a simulator study of an externally blown flap STOL aircraft
A piloted simulation study has been made of typical landing approaches with an externally blown flap STOL aircraft to ascertain a realistic dispersion of parameter values at both the flare window and touchdown. The study was performed on a fixed-base simulator using standard cockpit instrumentation. Six levels of stability and control augmentation were tested during a total of 60 approaches (10 at each level). A detached supplement containing computer printouts of the flare-window and touchdown conditions for all 60 runs has been prepared
Aerodynamic design and analysis system for supersonic aircraft. Part 1: General description and theoretical development
An integrated system of computer programs has been developed for the design and analysis of supersonic configurations. The system uses linearized theory methods for the calculation of surface pressures and supersonic area rule concepts in combination with linearized theory for calculation of aerodynamic force coefficients. Interactive graphics are optional at the user's request. This part presents a general description of the system and describes the theoretical methods used
A system for aerodynamic design and analysis of supersonic aircraft. Part 4: Test cases
An integrated system of computer programs was developed for the design and analysis of supersonic configurations. The system uses linearized theory methods for the calculation of surface pressures and supersonic area rule concepts in combination with linearized theory for calculation of aerodynamic force coefficients. Interactive graphics are optional at the user's request. Representative test cases and associated program output are presented
Irrational mode locking in quasiperiodic systems
A model for ac-driven systems, based on the
Tang-Wiesenfeld-Bak-Coppersmith-Littlewood automaton for an elastic medium,
exhibits mode-locked steps with frequencies that are irrational multiples of
the drive frequency, when the pinning is spatially quasiperiodic. Detailed
numerical evidence is presented for the large-system-size convergence of such a
mode-locked step. The irrational mode locking is stable to small thermal noise
and weak disorder. Continuous time models with irrational mode locking and
possible experimental realizations are discussed.Comment: 4 pages, 3 figures, 1 table; revision: 2 figures modified, reference
added, minor clarification
Energy efficient transport technology: Program summary and bibliography
The Energy Efficient Transport (EET) Program began in 1976 as an element of the NASA Aircraft Energy Efficiency (ACEE) Program. The EET Program and the results of various applications of advanced aerodynamics and active controls technology (ACT) as applicable to future subsonic transport aircraft are discussed. Advanced aerodynamics research areas included high aspect ratio supercritical wings, winglets, advanced high lift devices, natural laminar flow airfoils, hybrid laminar flow control, nacelle aerodynamic and inertial loads, propulsion/airframe integration (e.g., long duct nacelles) and wing and empennage surface coatings. In depth analytical/trade studies, numerous wind tunnel tests, and several flight tests were conducted. Improved computational methodology was also developed. The active control functions considered were maneuver load control, gust load alleviation, flutter mode control, angle of attack limiting, and pitch augmented stability. Current and advanced active control laws were synthesized and alternative control system architectures were developed and analyzed. Integrated application and fly by wire implementation of the active control functions were design requirements in one major subprogram. Additional EET research included interdisciplinary technology applications, integrated energy management, handling qualities investigations, reliability calculations, and economic evaluations related to fuel savings and cost of ownership of the selected improvements
A linearized theory method of constrained optimization for supersonic cruise wing design
A linearized theory wing design and optimization procedure which allows physical realism and practical considerations to be imposed as constraints on the optimum (least drag due to lift) solution is discussed and examples of application are presented. In addition to the usual constraints on lift and pitching moment, constraints are imposed on wing surface ordinates and wing upper surface pressure levels and gradients. The design procedure also provides the capability of including directly in the optimization process the effects of other aircraft components such as a fuselage, canards, and nacelles
Anisotropic evolution of D-dimensional FRW spacetime
We examine the time evolution of the D=d+4 dimensional Einstein field
equations subjected to a flat Robertson-Walker metric where the 3D and
higher-dimensional scale factors are allowed to evolve at different rates. We
find the exact solution to these equations for a single fluid component, which
yields two limiting regimes offering the 3D scale factor as a function of the
time. The fluid regime solution closely mimics that described by 4D FRW
cosmology, offering a late-time behavior for the 3D scale factor after becoming
valid in the early universe, and can give rise to a late-time accelerated
expansion driven by vacuum energy. This is shown to be preceded by an earlier
volume regime solution, which offers a very early-time epoch of accelerated
expansion for a radiation-dominated universe for d=1. The time scales
describing these phenomena, including the transition from volume to fluid
regime, are shown to fall within a small fraction of the first second when the
fundamental constants of the theory are aligned with the Planck time. This
model potentially offers a higher-dimensional alternative to scalar-field
inflationary theory and a consistent cosmological theory, yielding a unified
description of early- and late-time accelerated expansions via a 5D spacetime
scenario.Comment: Title changed from "A possible higher-dimensional alternative to
scalar-field inflationary theory". Several new results have been added
including a predicted lower- and upper-bound on the time scales marking the
end of an early-time inflationary epoch and the beginning of an FRW epoch for
d=
Collectivity and agency in remembering and reconciliation.
This paper examines how British war veterans fold together war time and post war experiences in practices of remembering and reconciliation. We examine these practices as networks of association between British ex-servicemen (veterans) and the people, places and circumstances associated with their experiences as prisoners in Japan during WW2. We focus on the experience of World War 2 British ex-servicemen (veterans) who were prisoners of war in Far East. During their period of captivity they worked to build Thai-Burma Railway before transfer to a copper mine in Japan. Some 50 years later they participated in a "reconciliation trip" to Japan. We discuss two related issues. First, how and in what ways are the post war lives and war time experiences of these veterans gathered up in the emergent collectivity of such practices? In other words in what ways do these practices emerge and sustain themselves as a process of collection and dispersion of circulating reference in networks of association between people places and things. Second, we examine how accounts of redemption (claims to the consequences of experience as being other than you would expect them to be) create the basis for emergent forms of agency and settlement in expanding networks of remembering and reconciliation
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