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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Flaring arches. III - The subflare of June 27, 1980, and its related extended arch

Detailed H-alpha, UV-line, and X-ray observations are presented of an extended arch that developed as a consequence of a compact subflare to a length of 300,000 km, in an 'included' magnetic polarity of low magnetic field strength. This great arch was preceded by one an order of magnitude smaller, which masked the polarity inversion line filament in the subflare's early phase. The fact that both arches were simultaneously observed in all spectral domains, as well as their fine structure in H-alpha, is explainable only in terms of an arch composition that encompassed several unresolved portions of material having widely different temperatures.

Fontenla, Juan M.↗
NASA NTRS1989

Flaring arches. II - Events in the arch system of 6/7 November, 1980

A characterization is developed for the 57,000-km long arch-shaped coronal structure of November 6, 1980, which became the site, first, of 13 quasi-periodic X-ray brightenings, and then of a series of 17 flaring arches. A comparison of H-alpha, O V, and X-ray data for the SB arch has qualitatively confirmed that a hot conduction front producing X-rays in the least dense plasma is first present, and is followed by a decelerating, denser plasma bulk in O V, with an eventual, still-further-decelerating very dense plasma becoming visible in H-alpha emission.

Svestka, Zdenek↗
DOE OSTI2026

ARCH Technology Snapshot Autonomous Robot Control Hierarchy (ARCH): A universal software system that removes the need to rebuild robotic software for every new platform or task

Robots are increasingly used to perform repetitive, hazardous, and time-sensitive tasks, improving safety and operational efficiency. However, most robotic systems remain difficult to adapt because they are tightly tied to specific hardware and require extensive reprogramming for each new configuration.

42 ENGINEERING↗
DOE OSTI2025

ARCH: Large-scale knowledge graph via aggregated narrative codified health records analysis

Objective: Electronic health record (EHR) systems contain a wealth of clinical data stored as both codified data and free-text narrative notes (NLP). The complexity of EHR presents challenges in feature representation, information extraction, and uncertainty quantification. Here, to address these challenges, we proposed an efficient Aggregated naRrative Codified Health (ARCH) records analysis to generate a large-scale knowledge graph (KG) for a comprehensive set of EHR codified and narrative features. Methods: Using data from 12.5 million Veterans Affairs patients, ARCH first derives embedding vectors and generates similarities along with associated p-values to measure the strength of relatedness between clinical features with statistical certainty quantification. Next, ARCH performs a sparse embedding regression to remove indirect linkage between features to build a sparse KG. Finally, ARCH was validated on various clinical tasks, including detecting known relationships between entity pairs, predicting drug side effects, disease phenotyping, as well as sub-typing Alzheimer’s disease patients. Results: ARCH produces high-quality clinical embeddings and KG for over 60,000 codified and narrative EHR concepts. The KG and embeddings are visualized in the R-shiny powered web-API.3 ARCH achieved high accuracy in detecting EHR concept relationships, with AUCs of 0.926 (codified) and 0.861 (NLP) for similar EHR concepts, and 0.810 (codified) and 0.843 (NLP) for related pairs. It detected drug side effects with a 0.723 AUC, which improved to 0.826 after fine-tuning. Using both codified and NLP features, the detection power increased significantly. Compared to other methods, ARCH has superior accuracy and enhances weakly supervised phenotyping algorithms’ performance. Notably, it successfully categorized Alzheimer’s patients into two subgroups with varying mortality rates. Conclusion: The proposed ARCH algorithm generates large-scale high-quality semantic representations and knowledge graph for both codified and NLP EHR features, useful for a wide range of predictive modeling tasks.

Electronic health records↗
NASA NTRS1989

Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

Thomas, John H.↗
NASA NTRS1982

Properties of coronal arches

The properties of coronal arches located on the peripheries of active regions, observed during a sounding rocket flight on March 8, 1973, are discussed. The arches are found to overlie filament channels and their footpoints are traced on locations on the perimeters of supergranulation cells. The arches have a wide range of lengths although their widths are well approximated by the value 2.2 x 10 to the 9th cm. Comparison of the size of the chromospheric footprint with the arc width indicates that arches do not always expand as they ascend into the corona. The electron temperatures and densities of the plasma contained in the arches were measured and the pressure calculated; typical values are 2-million K, 1 x 10 to the 9th/cu cm, and 0.2 dyne/sq cm, respectively. The variation of these parameters with position along the length of the arch indicates that the arches are not in hydrostatic equilibrium.

Davis, J. M.↗
NASA NTRS1972

Analysis of an arched outer-race ball bearing considering centrifugal forces

A Newton-Raphson method of iteration was used in evaluating the radial and axial projection of the distance between the ball center and the outer raceway groove curvature center (V and W). Fatigue life evaluations were made. The similar analysis of a conventional bearing can be directly obtained from the arched bearing analysis by simply letting the amount of arching be zero (g = 0) and not considering equations related to the unloaded half of the outer race. The analysis was applied to a 150-mm angular contact ball bearing. Results for life, contact loads, and angles are shown for a conventional bearing (g = 0) and two arched bearings (g = 0.127 mm (0.005 in.), and 0.254 mm (0.010 in.)). The results indicate that an arched bearing is highly desirable for high speed applications. In particular, for a DN value of 3 million (20,000 rpm) and an applied axial load of 4448 N (1000 lb), an arched bearing shows an improvement in life of 306 percent over that of a conventional bearing. At 4.2 million DN (28,000 rpm), the corresponding improvement is 340 percent. It was also found for low speeds, the arched bearing does not offer the advantages that it does for high speed applications.

Hamrock, B. J.↗
NASA NTRS1987

Optimization of shallow arches against instability using sensitivity derivatives

The author discusses the problem of optimization of shallow frame structures which involve a coupling of axial and bending responses. A shallow arch of a given shape and of given weight is optimized such that its limit point load is maximized. The cross-sectional area, A(x) and the moment of inertia, I(x) of the arch obey the relationship I(x) = rho A(x) sup n, n = 1,2,3 and rho is a specified constant. Analysis of the arch for its limit point calculation involves a geometric nonlinear analysis which is performed using a corotational formulation. The optimization is carried out using a second-order projected Lagrangian algorithm and the sensitivity derivatives of the critical load parameter with respect to the areas of the finite elements of the arch are calculated using implicit differentation. Results are presented for an arch of a specified rise to span ratio under two different loadings and the limitations of the approach for the intermediate rise arches are addressed.

Kamat, Manohar P.↗
NASA NTRS1976

Association of X-ray arches with chromospheric neutral lines

Daily maps of magnetic neutral lines derived from H-alpha observations have been superimposed on solar X-ray images for the period from June 15 to 30, 1973. Nearly all X-ray-emitting structures consist of systems of arches covering chromospheric neutral lines. Areas of low emissivity, coronal holes, appear as the areas between arcades of arches. The presence of a coronal hole, therefore, is determined by the spacing between neutral lines and the scale of the arches over those neutral lines. X-ray emissivity on the solar disk extends from neutral lines in proportion to the vertical and horizontal scale of the arches over those neutral lines. Increasing scale of arches corresponds with increasing age of magnetic fields associated with the neutral line. All X-ray filament cavities coincided with neutral lines, but filaments appeared under cavities for only part of their length and for only a fraction of the disk passage.

Mcintosh, P. S.↗
NASA NTRS1989

The footpoints of giant arches

H-alpha photographs are presented, which show chromospheric footpoints of the giant post-flare arches discovered by the Hard X-ray Imaging Spectrometer on the SMM satellite. The photographs display chromospheric signatures associated with five sequential giant arch events observed during November 6-10, 1980. The sets of footpoints at both ends of the arches have very slow brightness variations correlated in time with the brightness variations of the X-ray arches. The identifications of the two sets of footpoints is confirmed by current-free modeling of the coronal magnetic field (Kopp and Poletto, 1989). Possible explanations for the giant arch phenomenon are discussed.

Martin, Sara F.↗
NASA NTRS1990

Siphon flows in isolated magnetic flux tubes. III - The equilibrium path of the flux-tube arch

It is shown how to calculate the equilibrium path of a thin magnetic flux tube in a stratified, nonmagnetic atmosphere when the flux tube contains a steady siphon flow. The equilbrium path of a static thin flux tube in an infinite stratified atmosphere generally takes the form of a symmetric arch of finite width, with the flux tube becoming vertical at either end of the arch. A siphon flow within the flux tube increases the curvature of the arched equilibrium path in order that the net magnetic tension force can balance the inertial force of the flow, which tries to straighten the flux tube. Thus, a siphon flow reduces the width of the arched equilibrium path, with faster flows producing narrower arches. The effect of the siphon flow on the equilibrium path is generally greater for flux tubes of weaker magnetic field strength. Examples of the equilibrium are shown for both isothemal and adiabatic siphon flows in thin flux tubes in an isothermal external atmosphere.

Thomas, John H.↗
NASA NTRS1973

Ball motion and sliding friction in an arched outer race ball bearing

The motion of the ball and sliding friction in an arched outer race ball bearing under thrust loads is determined. Fatigue life evaluations were made. The analysis is applied to a 150 millimeter bore ball bearing. The results indicated that for high speed-light load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be an optimal. For an arched bearing it was also found that a considerable amount of spinning occurs at the outer race contacts.

Hamrock, B. J.↗
NASA NTRS1974

Ball motion and sliding friction in an arched outer-race ball bearing

The motion of the ball and sliding friction in an arched outer-race ball bearing under thrust load is analyzed. Fatigue life evaluations were made. The analysis is applied to a 150-millimeter-bore ball bearing. The results indicated that for high-speed light-load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be optimal. Also, for an arched bearing a considerable amount of spinning occurs at the outer-race contacts.

Hamrock, B. J.↗
NASA NTRS1974

Ball motion and sliding friction in an arched outer race ball bearing

The motion of the ball and sliding friction in an arched outer-race ball bearing under thrust load is determined. Fatigue life evaluations were made. The analysis is applied to a 150 millimeter bore ball bearing. The results indicated that for high speed-light load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be an optimal. For an arched bearing it was also found that a considerable amount of spinning occurs at the outer race contacts.

Hamrock, B. J.↗
NASA NTRS1983

The Ponta Grossa Arch: A proposal for ts configuration and evolution from the interpretation of remote sensing data

Visual analysis of MSS imagery was used to construct a map of dikes in a wide area of the Ponta Grossa Arch both in the Parana Basin and its basement. Analysis of the map by photographic methods defined the zone of highest density of the dikes, and some aspects of the longitudinal and transverse heterogeneities, as well as localized the apex of the Arch. Borders of the Arch were also suggested. Field investigations confirmed the position of the apex of the flexure on Palezoic sediments and pre-lava Mesozoic sediments. Controversial aspects of the relative absence of dikes in certain units or lithologies and the composition of intrusions surrounding the city of Castro were observed. The apparent synchronism between the activity of the Parana Basin and the Arch is discussed as well as the frequent inverse characteristics of vertical movements. The similarity of rocks in Brazil and Africa is also considered.

Parada, N. D. J.↗
NASA NTRS1982

The growth of filaments by the condensation of coronal arches

A model of filament formation based on the condensation of coronal arches is described. The condensation results from initiating the radiative instability within an arch by superimposing a transient energy supply upon the steady state heating mechanism. The transient energy supply increases the density within the arch so that when it is removed the radiative losses are sufficient to lead to cooling below the minimum in the power loss curve. Times from the initial formation of the condensation to its temperature stabilization as a cool filament have been calculated for various initial conditions. They lie in the range 10,000-100,000 s with the majority of the time spent above a temperature of 1 x 10 to the 6th K. Under the assumption that the condensation of a single arch forms an element of the filament, a complete filament requires the condensation of an arcade of loops. Using experimentally derived parameters, filament densities of 10 to the 11th to 10 to the 12th per cu cm can be obtained.

Davis, J. M.↗
NASA NTRS1988

The vertical structure of arch filament systems in solar emerging flux regions

The paper studies the vertical velocity of arch filaments in emerging flux regions by measuring their proper motion near the limb in H-alpha filtergrams and their radial velocity near the disk center in H-alpha spectrograms. Both show that arch filaments rise at a velocity between 10 and 15 km/s. The possible mechanisms producing this high velocity are discussed. None of them is satifactory, but it appears that the unloading of the arches by outflow must play a role. From the strength of H-alpha emission and D3 absorption, the temperature of arch filaments is estimated at 6000-15,000 K and the density at 10 to the 11th-12th/cu cm.

Chou, Dean-Yi↗
NASA NTRS2007

The Coronal-Dimming Footprint of a Streamer-Puff Coronal Mass Ejection: Confirmation of the Magnetic-Arch-Blowout Scenario

A streamer puff is a recently identified variety of coronal mass ejection (CME) of narrow to moderate width. It (1) travels our along a streamer, transiently inflating the streamer but leaving it largely intact, and (2) occurs in step with a compact ejective flare in an outer flank of the base of the streamer. These aspects suggest the following magnetic-arch-blowout scenario for the production of these CMEs: the magnetic explosion that produces the flare also produces a plasmoid that explodes up the leg of an outer loop of the arcade base of the streamer, blows out the top of this loop, and becomes the core of the CME. In this paper, we present a streamer-puff CME that produced a coronal-dimming footprint. The coronal dimming, its magnetic setting, and the timing and magnetic setting of a strong compact ejective flare within the dimming footprint nicely confirm the magnetic-arch-blowout scenario. From these observations, together with several published cases of a trans-equatorial CME produced in tandem with an ejective flare or filament eruption that was far offset from directly under the CME, we propose the following. Streamer-puff CMEs are a subclass (one variety) of a broader class of "over-and-out" CMEs that are often much larger than streamer puffs but are similar to them in that they are produced by the blowout of a large quasi-potential magnetic arch by a magnetic explosion that erupts from one foot of the large arch, where it is marked by a filament eruption and/or an ejective flare.

Moore, Ronald L.↗