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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The magnetic geometry and structure of the giant post-flare arch of 21-22 May, 1980

The photospheric line-of-sight magnetic field distribution of a giant post-flare arch observed on May 21-22, 1980 is used to determine the three-dimensional topology of the coronal field above the flare site. It is proposed that the arch is the by-poduct of magnetic reconnection occurring far above the flare site. The field lines undergoing reconnection link more distant parts of the active region and are topologically distinct from those which thread the underlying post-flare loops.

Poletto, G.↗
NASA NTRS1990

Thermal modeling of the NASA-Ames Research Center Cryogenic Optical Test Facility and a single-arch, fused-natural-quartz mirror

A thermal model of the dewar and optical system of the Cryogenic Optical Test Facility at NASA-Ames Research Center was developed using the computer codes SINDA and MONTE CARLO. The model was based on the geometry, boundary conditions, and physical properties of the test facility and was developed to investigate heat transfer mechanisms and temperatures in the facility and in test mirrors during cryogenic optical tests. A single-arch, fused-natural-quartz mirror was the first mirror whose thermal loads and temperature distributions were modeled. From the temperature distribution, the thermal gradients in the mirror were obtained. The model predicted that a small gradient should exist for the single arch mirror. This was later verified by the measurement of mirror temperatures. The temperatures, predicted by the model at various locations within the dewar, were in relatively good agreement with the measured temperatures. The model is applicable to both steady-state and transient cooldown operations.

Ng, Y. S.↗
NASA NTRS1979

Dental Arch Wire

Straightening teeth is an arduous process requiring months, often years, of applying corrective pressure by means of arch wires-better known as brace-which may have to be changed several times in the course of treatment. A new method has been developed by Dr. George Andreasen, orthodontist and dental scientist at the University of Iowa. The key is a new type of arch wire material, called Nitinol, with exceptional elasticity which helps reduce the required number of brace changes. An alloy of nickel and titanium, Nitinol was originally developed for aerospace applications by the Naval Ordnance Laboratory, now the Naval Surface Weapons Laboratory, White Oaks, Maryland. NASA subsequently conducted additional research on the properties of Nitinol and on procedures for processing the metal.

Source record↗
DOE OSTI2021

Flow and Arching of Biomass Particles in Wedge-Shaped Hoppers

Poor understanding of the flow behavior of granular biomass material poses great challenges for the bioenergy industry, as the equipment functioning time is significantly reduced by handling issues like screw feeder clogging and hopper arching. In this work, the flow behavior of loblolly pine chips, including the mass flow rate and the critical outlet width, in a wedge-shaped hopper is investigated by combining physical experiments and numerical simulations. Comprehensive characterization of the flow response affected by the two material attributes (initial packing, particle density) and the three operational parameters (hopper outlet width, hopper inclination, and surcharge) is conducted. The results show that the hopper outlet width linearly controls the mass flow rate while the hopper inclination angle controls the critical outlet size. The packing determines whether the flow is smooth or surging, and the surcharge-induced compaction creates flow impedance. The magnitude of these influences varies from a slender hopper with a low inclination angle to a flat-bottom silo. These findings provide guidance for hopper operation in the material handling industry and shed light on the construction of a novel design method for material handling equipment in biorefineries.

09 BIOMASS FUELS↗
NASA NTRS1966

Calculating arch dams

Approximation methods used in design of thin walled shells for hydroelectric power plant arch dams

POWER PLANT↗
NASA NTRS1969

On optimal arches

Optimal inextensional buckling of uniformly loaded simply supported arches with large opening angle

Budiansky, B.↗
NASA NTRS1971

Dynamic buckling of shallow arches

Symmetric and asymmetric dynamic buckling of shallow elastic arches under uniform loads, using nonlinear finite difference method

Barton, F. W.↗
NASA NTRS1972

ATM/cable arch and beam structural test program

The structural testing is described of an Apollo Telescope Mount (ATM) cable arch and beam assembly, using static loads to simulate the critical conditions expected during transportation and launch of the ATM. All test objectives were met. Stress and deflection data show that the assembly is structurally adequate for use in the ATM.

Housley, J. A.↗
NASA NTRS1972

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

Thrust-load analysis of a 150-mm angular contact ball bearing, taking into account centrifugal forces but omitting gyroscopics, elastohydrodynamics, and thermal effects. A Newton-Raphson method of iteration is used to evaluate the radial and axial projection of the distance between the ball center and the outer raceway groove curvature center. Fatigue life of the bearing is evaluated. Results for life, contact loads, and angles are given for a conventional bearing and two arched bearings.

Hamrock, B. J.↗
NASA NTRS1983

Double arch mirror study. Part 1: Preliminary engineering report

In the proposed design, the NASA AMES 20-in double arch mirror is supported by three clamp and flexure assemblies. The mirror clamp consists of a T-shaped Invar-36 member that goes into a similarly shaped socket in the back of the mirror. The mirror socket is made oversize and contacts the clamp only along the conical surface. The clamp is preloaded by a spring washer and pulls the mirror into contact with the flexure. The clamp is then inserted into the mirror socket through a cutout, is rotated 90 deg, and is then pinned in place. Loading conditions considered in socket design are discussed as well as stress in the socket and clamp. Flexure geometry and stress are examined as well as the effects of flexure error and of mirror cell error.

Vukobratovich, D.↗
NASA NTRS1983

Double arch mirror study. Part 2: Engineering analysis report

A method of mounting a cryogenically cooled, lightweight, double arch, class mirror for infrared, astronomical telescopes was developed. A 50 cm, fused silica mirror was modified for use in a new mount configuration. The flexures and the finite element analysis of the mirror stresses are reported.

Iraninejad, B.↗
NASA NTRS1983

Double arch mirror study. Part 3: Fabrication and test report

A method of mounting a cryogenically cooled, lightweight, double arch, glass mirror was developed for infrared, astronomical telescopes such as the Space Infrared Telescope Facility (SIRTF). A 50 cm, fused silica mirror which was previously fabricated was modified for use with a new mount configuration. This mount concept was developed. The modification of the mirror, the fabrication of the mirror mount, and the room temperature testing of the mounted mirror are reported. A design for a SIRTF class primary mirror is suggested.

Vukobratovich, D.↗
NASA NTRS1983

Double arch mirror study

The development of a method of mounting light weight glass mirrors for astronomical telescopes compatible with the goals of the Shuttle Infrared Telescope Facility (SIRTF) was investigated. A 20 in. diameter double arch lightweight mirror previously fabricated was modified to use a new mount configuration. This mount concept was developed and fabricated. The mounting concept of the double mounting mirror is outlined. The modifications made to the mirror, fabrication of the mirror mount, and room temperature testing of the mirror and mount and the extension of the mirror and mount concept to a full size (40 in. diameter) primary mirror for SIRTF are discussed.

Vukobratovich, D.↗
NASA NTRS1984

Do the Arching HI Filaments Show in Local Reddening Data?

Probable dust counterparts of arching structures are investigated in two cases: (1) the Eridanus expanding shell; and (2) the extended Sco-Cen feature. Color excess data may be used to derive distance and dimension estimates of these structures. Color excesses from two areas SA 121 and SA 144 situated on the position of the 3.2 to 6.3 km/s velocity-slice are applied. Some stratification of the color excesses is noticed for both areas but extreme patchiness typifies particularly the dust in the SA 144 region.

Knude, J.↗
NASA NTRS1986

X-ray imaging of flare loops and coronal arches

HXIS (Hard X-ray Imaging Spectrometer) results related to preflare, flare-decay, and post-flare phases in the solar corona are summarized. Particularly discussed are miniflares, long-lived X-ray enhancements along filament channels, flare precursors (some signifying the flare position, others possibly related to the onset of mass ejections), growth of post-flare loops, images of sites of field-line reconnections late in the flare development, giant post-flare coronal arches with energy contents comparable to coronal transients, and hot loops interconnecting active regions. The extremely low HXIS background, in particular, made it possible to discover many new, previously unknown features in the solar corona. Also emphasized are some problems that have appeared during the evaluation of HXIS data, for the benefit of those who plan future hard X-ray imaging experiments.

Svestka, Z.↗
NASA NTRS1987

Non-isothermal elastoviscoplastic snap-through and creep buckling of shallow arches

The problem of buckling of shallow arches under transient thermomechanical loads is investigated. The analysis is based on nonlinear geometric and constitutive relations, and is expressed in a rate form. The material constitutive equations are capable of reproducing all non-isothermal, elasto-viscoplastic characteristics. The solution scheme is capable of predicting response which includes pre and postbuckling with creep and plastic effects. The solution procedure is demonstrated through several examples which include both creep and snap-through behavior.

Simitses, G. J.↗