11,083 research outputs found
Generation of pseudo-random numbers
Practical methods for generating acceptable random numbers from a variety of probability distributions which are frequently encountered in engineering applications are described. The speed, accuracy, and guarantee of statistical randomness of the various methods are discussed
Navigation and guidance requirements for commercial VTOL operations
The NASA Langley Research Center (LaRC) has undertaken a research program to develop the navigation, guidance, control, and flight management technology base needed by Government and industry in establishing systems design concepts and operating procedures for VTOL short-haul transportation systems in the 1980s time period. The VALT (VTOL Automatic Landing Technology) Program encompasses the investigation of operating systems and piloting techniques associated with VTOL operations under all-weather conditions from downtown vertiports; the definition of terminal air traffic and airspace requirements; and the development of avionics including navigation, guidance, controls, and displays for automated takeoff, cruise, and landing operations. The program includes requirements analyses, design studies, systems development, ground simulation, and flight validation efforts
Boundary conditions for free surface inlet and outlet\ud problems
We investigate and compare the boundary conditions that are to be applied to free surface problems involving inlet and outlets of Newtonian fluid, typically found in coating processes. The flux of fluid is a priori known at an inlet, but unknown at an outlet, where it is governed by the local behaviour near the film-forming meniscus. In the limit of vanishing capillary number Ca it is well-known that the flux scales with Ca2/3, but this classical result is nonuniform as the contact angle approaches . By examining this limit we find a solution that is uniformly valid for all contact angles. Furthermore, by considering the far-field behaviour of the free surface we show that there exists a critical capillary number above which the problem at an inlet becomes over-determined. The implications of this result for the modelling of coating flows are discussed
Measurement of the elastic scattering cross section of neutrons from argon and neon
Background: The most significant source of background in direct dark matter
searches are neutrons that scatter elastically from nuclei in the detector's
sensitive volume. Experimental data for the elastic scattering cross section of
neutrons from argon and neon, which are target materials of interest to the
dark matter community, were previously unavailable. Purpose: Measure the
differential cross section for elastic scattering of neutrons from argon and
neon in the energy range relevant to backgrounds from (alpha,n) reactions in
direct dark matter searches. Method: Cross-section data were taken at the
Triangle Universities Nuclear Laboratory (TUNL) using the neutron
time-of-flight technique. These data were fit using the spherical optical
model. Results: The differential cross section for elastic scatting of neutrons
from neon at 5.0 and 8.0 MeV and argon at 6.0 MeV was measured. Optical-model
parameters for the elastic scattering reactions were determined from the best
fit to these data. The total elastic scattering cross section for neon was
found to differ by 6% at 5.0 MeV and 13% at 8.0 MeV from global optical-model
predictions. Compared to a local optical-model for 40Ar, the elastic scattering
cross section was found to differ from the data by 8% at 6.0 MeV. Conclusions:
These new data are important for improving Monte-Carlo simulations and
background estimates for direct dark matter searches and for benchmarking
optical models of neutron elastic scattering from these nuclei
Number 3 (November 1976)
Status of the Watercress Darter. By W.M. Howell and A. Black, plus News Notes, 4 pp
Restructurable Controls
Restructurable control system theory, robust reconfiguration for high reliability and survivability for advanced aircraft, restructurable controls problem definition and research, experimentation, system identification methods applied to aircraft, a self-repairing digital flight control system, and state-of-the-art theory application are addressed
Clarifying Analysis and Interpretation in Grounded Theory: Using a Conditional Relationship Guide and Reflective Coding Matrix
Although qualitative methods, grounded theory included, cannot be reduced to formulaic procedures, research tools can clarify the process. The authors discuss two instruments supporting grounded theory analysis and interpretation using two examples from doctoral students. The conditional relationship guide contextualizes the central phenomenon and relates categories linking structure with process. The reflective coding matrix serves as a bridge to the final phase of grounded theory analysis, selective coding and interpretation, and, ultimately, to substantive theory generation
Microwave soil moisture measurements and analysis
An effort to develop a model that simulates the distribution of water content and of temperature in bare soil is documented. The field experimental set up designed to acquire the data to test this model is described. The microwave signature acquisition system (MSAS) field measurements acquired in Colby, Kansas during the summer of 1978 are pesented
A Near-Infrared Spectroscopic Study of the Accreting Magnetic White Dwarf SDSS J121209.31+013627.7 and its Substellar Companion
The nature of the excess near-infrared emission associated with the magnetic
white dwarf commonly known as SDSS 1212 is investigated primarily through
spectroscopy, and also via photometry. The inferred low mass secondary in this
system has been previously detected by the emission and variation of H,
and the m spectral data presented here are consistent with the
presence of a late L or early T dwarf. The excess flux seen beyond 1.5 m
in the phase-averaged spectrum is adequately modeled with an L8 dwarf
substellar companion and cyclotron emission in a 7 MG magnetic field. This
interesting system manifests several observational properties typical of
polars, and is most likely an old interacting binary with a magnetic white
dwarf and a substellar donor in an extended low state.Comment: 28 pages, 5 figures, Accepted to Ap
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