The Influence of the Testing Machine on the Buckling of Cylindrical Shells Under Axial Compression

Testing machine influence on buckling of cylindrical shells under axial compressio

Experimental investigation of the effect of general imperfections on the buckling of cylindrical shells

Imperfection survey data on cylindrical shells before and during axial compression loading up to buckling loa

A Mechanical Model for Elastic Fiber Microbuckling

A two-dimensional mechanical model is presented to predict the compressive strength of unidirectional fiber composites using technical beam theory and classical elasticity. First, a single fiber resting on a matrix half-plane is considered. Next, a more elaborate analysis of a uniformly laminated, unidirectional fiber composite half-plane is presented. The model configuration incorporates a free edge which introduces a buckling mode that originates at the free edge and decays into the interior of the half-plane. It is demonstrated that for composites of low volume fraction (<0.3), this decay mode furnishes values of buckling strain that are below the values predicted by the Rosen (1965) model. At a higher volume fraction the buckling mode corresponds to a half wavelength that is in violation of the usual assumptions of beam theory. Causes for deviations of the model prediction from existing experimental results are discussed

Thermal/structural analysis of a transpiration cooled nozzle

The 8-foot High Temperature Tunnel (HTT) at LaRC is a combustion driven, high enthalpy blow down wind tunnel. In Mar. 1991, during check out of the transpiration cooled nozzle, pieces of platelets were found in the tunnel test section. It was determined that incorrect tolerancing between the platelets and the housing was the primary cause of the platelet failure. An analysis was performed to determine the tolerance layout between the platelets and the housing to meet the structural and performance criteria under a range of thermal, pressure, and bolt preload conditions. Three recommendations resulted as a product of this analysis

Millstone Hill Thomson Scatter Results for 1973

During 1973, the vertically-directed incoherent scatter radar at Millstone Hill (42.6°N, 71.5°W) was employed to measure electron density, electron and ion temperature and vertical ion velocity in the F-region over periods of 24 hours one or two times per month. The observations spanned the height interval 200-900 km approximately, and achieved a time resolution of about 30 minutes. This report presents the results of these measurements in a set of contour diagrams. For a number of the days, the results have been used to derive the diurnal variation of the temperature of the neutral atmosphere above 300 km (the exospheric temperature) as well as the speed of the neutral wind in the magnetic meridian plane at this altitude. These results were used to define a model for the pressure variation in the thermosphere over Millstone whose E-W variation is set by the observed temperature variation, and whose N-S variation was adjusted to reproduce the observed winds calculated by solving momentum equations for the neutral air. These results, together with similar results obtained using data gathered over the six-year period 1970-1975 have been used in a study of the seasonal and sunspot cycle variation of the mean meridional and zonal winds. Also reported are the results of a study of the effect of magnetic storms on the thermospheric winds observed over Millstone Hill

Solar Polar Fields During Cycles 21 --- 23: Correlation with Meridional Flows

We have examined polar magnetic fields for the last three solar cycles, {$\it{viz.}$}, cycles 21, 22 and 23 using NSO Kitt Peak synoptic magnetograms. In addition, we have used SoHO/MDI magnetograms to derive the polar fields during cycle 23. Both Kitt Peak and MDI data at high latitudes (78${^{\circ}}$--90${^{\circ}}$) in both solar hemispheres show a significant drop in the absolute value of polar fields from the late declining phase of the solar cycle 22 to the maximum of the solar cycle 23. We find that long term changes in the absolute value of the polar field, in cycle 23, is well correlated with changes in meridional flow speeds that have been reported recently. We discuss the implication of this in influencing the extremely prolonged minimum experienced at the start of the current cycle 24 and in forecasting the behaviour of future solar cycles.Comment: 4 Figures 11 pages; Revised version under review in Solar Physic

Preliminary Reconnaissance Water Quality Survey of the Buffalo National River

In accordance with Contract No. CX 700030105, dated 12 February 1973, the University of Arkansas , Water Resources Resear ch Center is submitting a Preliminary Reconnaissance Water Quality Survey of the Buffalo National River. The Water Resources Research Center of Arkansas has supplied the necessary personnel and facil ities to perform a preliminary reconnaissance survey of the Buffalo National River of Arkansas with special emphasis placed on the establishment of both permanent and temporary benchmarks for water quality sampling. Preliminary water quality samples have been collected to make those chemical, physical, and biological analyses as defined by Mr . Roland H. Wauer and other Park Service personnel on 3 May 1973

Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helices

NGC 1316 is a giant, elliptical galaxy containing a complex network of dark, dust features. The morphology of these features has been examined in some detail using a Hubble Space Telescope, Advanced Camera for Surveys image. It is found that most of the features are constituted of long filaments. There also exist a great number of dark structures protruding inwards from the filaments. Many of these structures are strikingly similar to elephant trunks in H II regions in the Milky Way Galaxy, although much larger. The structures, termed mammoth trunks, generally are filamentary and often have shapes resembling the letters V or Y. In some of the mammoth trunks the stem of the Y can be resolved into two or more filaments, many of which showing signs of being intertwined. A model of the mammoth trunks, related to a recent theory of elephant trunks, is proposed. Based on magnetized filaments, the model is capable of giving an account of the various shapes of the mammoth trunks observed, including the twined structures.Comment: Accepted for publication in Astrophysics & Space Scienc