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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Operational unification of finite difference methods for numerical integration of ordinary differential equations
An efficient means of storing data in a first-order predicate calculus theorem-proving system is described. The data structure is oriented for large scale question-answering (QA) systems. An algorithm is outlined which uses the data structure to unify a given literal in parallel against all literals in all clauses in the data base. The data structure permits a compact representation of data within a QA system. Some suggestions are made for heuristics which can be used to speed-up the unification algorithm in systems.
The transition of a number of hadronic process characteristics to a certain universal regime is interpreted as an indication to the early origination of the unification regime of the interactions.
Information is increasingly becoming a strategic resource in all societies and economies. The NASA Scientific and Technical Information (STI) Program has initiated a modernization program to address the strategic importance and changing characteristics of information. This modernization effort applies new technology to current processes to provide near-term benefits to the user. At the same time, we are developing a long-term modernization strategy designed to transition the program to a multimedia, global 'library without walls.' Notwithstanding this modernization program, it is recognized that no one information center can hope to collect all the relevant data. We see information and information systems changing and becoming more international in scope. We are finding that many nations are expending resources on national systems which duplicate each other. At the same time that this duplication exists, many useful sources of aerospace information are not being collected because of resource limitations. If nations cooperate to develop an international aerospace information system, resources can be used efficiently to cover expanded sources of information. We must consider forming a coalition to collect and provide access to disparate, multidisciplinary sources of information, and to develop standardized tools for documenting and manipulating this data and information. In view of recent technological developments in information science and technology, as well as the reality of scarce resources in all nations, it is time to explore the mutually beneficial possibilities offered by cooperation and international resource sharing. International resources need to be mobilized in a coordinated manner to move us towards this goal. This paper reviews the NASA modernization program and raises for consideration new possibilities for unification of the various aerospace database efforts toward a cooperative international aerospace database initiative that can optimize the cost/benefit equation for all participants.
We describe a technique which makes it feasible to improve the performance of a language model derived from a manually constructed unification grammar, using low-quality untranscribed speech data and a minimum of human annotation. The method is on a medium-vocabulary spoken language command and control task.
TeV emission from BL Lacertae (BL) objects i s commonly modeled as Synchrotron-Self Compton (SSC) radiation from relativistically moving homogeneous plasma blobs. In the context of these models, the blob Lorentz factors needed to reproduce the corrected for absorption by the diffuse IR background (DIRB) TeV emission are large ($\delta \gtrsim 50$). The main reason for this is that stronger beaming eases the problem of the lack of $\sim$ IR-UV synchrotron seed photons needed to produce the de-absorbed $\sim $ few TeV peak of the spectral energy distribution (SED). However, such high Doppler factors are in strong disagreement with the unified scheme, according to which BLs are FR I radio galaxies with their jets closely aligned to the line of sight. Here, motivated by the detection of sub-luminal velocities in the sub-pc scale jets of the best studied TeV blazars, MKN 421 and MKN 501, we examine the possibility that the relativistic flows in the TeV BLs decelerate. In this case, the problem of the missing seed photons is solved because of Upstream Compton (UC) scattering, a process in which the upstream energetic electrons from the fast base of the flow 'see' the synchrotron seed photons produced in the slow part of the flow relativistically beamed. Modest Lorentz factors ($\Gamma \sim 15$), decelerating down to values compatible with the recent radio interferometric observations, reproduce the $\sim $ few TeV peak energy of these sources. Furthermore, such decelerating flows are shown to be in agreement with the BL - FR I unification, naturally reproducing the observed BL/FR I broadband luminosity ratios.
We present the 2D photoionization structure of the MHD winds of AGN accretion disks. We focus our attention on a specific subset of winds, those with poloidal currents that lead to density profiles n(r) \propto 1/r. We employ the code XSTAR to compute the local ionization balance, emissivities and opacity which are then used in the self-consistent transfer of radiation and ionization of a host of ionic species of a large number of elements over then entire poloidal plane. Particular attention is paid to the Absorption Measure Distribution (AMD), namely their hydrogen-equivalent column of these ions per logarithmic 7 interval, dN_H/dlog ? (? = L/n(r)r(sup 2) is the ionization parameter), which provides a measure of the winds' radial density profiles. For the given density profile, AMD is found to be independent of ?, in good agreement with analyses of Chandra and XMM data, suggesting the specific profile as a fundamental AGN property. Furthermore, the ratio of equatorial to polar column densities of these winds is \simeq 10(exp 4); as such, it is shown they serve as the "torus" necessary for AGN unification with phenomenology consistent with the observations. The same winds are also shown to reproduce the observed columns and velocities of C IV and Fe XXV of SAL QSOs once the proper ionizing spectra and inclination angles are employed.
We recently argued [21J that the collective properties. of radio loud active galactic nuclei point to the existence of two families of sources, one of powerful sources with single velocity jets and one of weaker jets with significant velocity gradients in the radiating plasma. These families also correspond to different accretion modes and therefore different thermal and emission line intrinsic properties: powerful sources have radiatively efficient accretion disks, while in weak sources accretion must be radiatively inefficient. Here, after we briefly review of our recent work, we present the following findings that support our unification scheme: (i) along the broken sequence of aligned objects, the jet kinetic power increases. (ii) in the powerful branch of the sequence of aligned objects the fraction of BLLs decreases with increasing jet power. (iii) for powerful sources, the fraction of BLLs increases for more un-aligned objects, as measured by the core to extended radio emission. Our results are also compatible with the possibility that a given accretion power produces jets of comparable kinetic power.
The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is >60 per cent, consistent with previous studies. The fraction of sources with UFOs is >34 per cent, >67 per cent of which also show WAs. The large dynamic range obtained when considering all the absorbers together, spanning several orders of magnitude in ionization, column, velocity and distance allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. In all the cases, the absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. These evidence strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The UFOs are likely launched from the inner accretion disc and the WAs at larger distances, such as the outer disc and/or torus. We argue that the observed parameters and correlations are, to date, consistent with both radiation pressure through Compton scattering and magnetohydrodynamic processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, show a sufficiently high mechanical power (at least approx 0.5 per cent of the bolometric luminosity) to provide a significant contribution to active galactic nuclei (AGN) feedback and thus to the evolution of the host galaxy. In this regard, we find possible evidence for the interaction of the AGN wind with the surrounding environment on large scales.
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This correspondence examines multiparameter generalizations of the Cramer-Rao (C-R) bound and related bounds from a new viewpoint. We derive a general class of bounds and show that Rao's generalization is the tightest (best) of the class. A bound reported by Zacks is another member of the class. This derivation of the C-R bound emphasizes its optimum nature. The relationship of the general class to Barankin bounds is also discussed.
Wind data measured on a 444-m tower located near Oklahoma City, Oklahoma, were used to investigate the structure of wind and turbulence in the height interval from 150 m to 1 km. The structure of wind and turbulence in the layer not encompassed by the existing design criteria was researched and ways for unifying the ground and inflight criteria were investigated. Steady state vertical wind profiles, directional wind component envelopes, wind shear, wind direction change, gust factor, and turbulence spectra are encompassed. A method is proposed for the specification of steady state wind profiles and shear envelopes for use in the region between 150 m and 1 km without altering in any way the existing design criteria. The data analyzed did not indicate a need for changing the existing criteria in regards to wind direction change, gust factor, or spectra of turbulence.
Techniques are described for determining the height of Mean Sea Level (MSL) at coastal sites from satellite altimetry. Such information is of value in the adjustment of continental leveling networks. Numerical results are obtained from the 1977 GEOS-3 altimetry data bank at Goddard Space Flight Center using the Bermuda calibration of the altimeter. Estimates are made of the heights of MSL at the leveling datums for Australia and a hypothetical Galveston datum for central North America. The results obtained are in reasonable agreement with oceanographic estimates obtained by extrapolation. It is concluded that all gravity data in the Australian bank AUSGAD 76 and in the Rapp data file for central North America refer to the GEOS-3 altimeter geoid for 1976.0 with uncertainties which do not exceed + or - 0.1 mGal.
The biochemical methods for determination of various parameters and factors during pre- and post-flight periods, as used by American and Soviet teams dealing with space flight medicine are compared. The emphasis is on the exchange of information on the study of the blood and urine content of space travelers before and after space flight. A series of electrolytic, enzymatic, and hormonal factors is discussed.
The theory and basic concepts for the development of a matter-antimatter domain cosmology are outlined within the framework of the grand unified gauge theory paradigm. It is shown how spontaneous CP symmetry breaking leads to such a domain sturcture in the universe. Astrophysical data such as the cosmic gamma-ray background spectrum, cosmic-ray p flux measurements, and galaxy clustering are found to favor this point of view. Future tests of this form of big-bang cosmology are suggested and discussed, including tests using deep underwater cosmic ray neutrino detectors.
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(Previously announced in STAR as N81-23986)
To facilitate the understanding of complex three-dimensional numerical models, advanced interactive color postprocessing techniques are introduced. These techniques are sufficiently flexible so that postprocessing difficulties arising from model size, geometric complexity, response variation, and analysis type can be adequately overcome. Finite element, finite difference, and boundary element models may be evaluated with the prototype postprocessor. Elements may be removed from parent models to be studied as independent subobjects. Discontinuous responses may be contoured including responses which become singular, and nonlinear color scales may be input by the user for the enhancement of the contouring operation. Hit testing can be performed to extract precise geometric, response, mesh, or material information from the database. In addition, stress intensity factors may be contoured along the crack front of a fracture model. Stepwise analyses can be studied, and the user can recontour responses repeatedly, as if he were paging through the response sets. As a system, these tools allow effective interpretation of complex analysis results.