20,753 research outputs found
Measurement of point velocities in turbulent liquid flow
Turbulent water flow velocity distribution using hot-wire anemometer and photographic technique
Deflections of beam columns on multiple supports
Lateral deflections of beam columns on multiple equally spaced supports are calculated using the STAGS nonlinear structural analysis computer program. Three lateral loadings are considered, uniform, linear, and uniform over only the center bay. Two types of boundary conditions are considered at the end supports, clamped, and simple support. The effect of an initial sinusoidal imperfection are considered. Deflections in the center and end bays of the beam columns are presented as a function of applied axial compressive load. As the number of bays becomes large, the effect of boundary conditions on the deflections in the center bays diminishes. For cases involving a uniform or linearly varying load, imperfections can have a much larger effect on deflections in the center bays than can lateral pressure
Current research on shear buckling and thermal loads with PASCO: Panel Analysis and Sizing Code
The PASCO computer program to obtain the detailed dimensions of optimum stiffened composite structural panels is described. Design requirements in terms of inequality constraints can be placed on buckling loads or vibration frequencies, lamina stresses and strains, and overall panel stiffness for each of many load conditions. General panel cross sections can be treated. An analysis procedure involving a smeared orthotropic solution was investigated. The conservatism in the VIPASA solution and the danger in a smeared orthotropic solution is explored. PASCO's capability to design for thermal loadings is also described. It is emphasized that design studies illustrate the importance of the multiple load condition capability when thermal loads are present
Buckling loads for stiffened panels subjected to combined longitudinal compression and shear loadings: Results obtained with PASCO, EAL, and STAGS computer
The shear buckling analyses used in PASCO are summarized. The PASCO analyses include the basic VIPASA analysis, which is essentially exact for longitudinal and transverse loads, and a smeared orthotropic solution which was added to alleviate a shortcoming in the VIPASA analysis. Buckling results are presented for six stiffened panels loaded by combinations of longitudinal compression and shear. The buckling results were obtained with the PASCO, EAL, and STAGS computer programs. The EAL and STAGS solutions were obtained with a fine finite element mesh and provide calculations for the entire range of combinations of longitudinal compression and shear loadings
Buckling loads of stiffened panels subjected to combined longitudinal compression and shear: Results obtained with PASCO, EAL, and STAGS computer programs
Buckling analyses used in PASCO are summarized with emphasis placed on the shear buckling analyses. The PASCO buckling analyses include the basic VIPASA analysis, which is essentially exact for longitudinal and transverse loads, and a smeared stiffener solution, which treats a stiffened panel as an orthotropic plate. Buckling results are then presented for seven stiffened panels loaded by combinations of longitudinal compression and shear. The buckling results were obtained with the PASCO, EAL, and STAGS computer programs. The EAL and STAGS solutions were obtained with a fine finite element mesh and are very accurate. These finite element solutions together with the PASCO results for pure longitudinal compression provide benchmark calculations to evaluate other analysis procedures
The Changing Pattern of Antarctic Botanical Studies
Some of the major changes which have characterized the study of botany within the Antarctic Botanical Zone are briefly reviewed. Almost all the work in the pre-IGY phase was of a taxonomic or distributional nature, being based principally on preserved material. Since the IGY however, an increasing emphasis is being placed on the study of living material, one result being the rapid development of ecological programmes which so far, have concentrated on problems of vegetation description, environmental analysis and experimental autecology. Thus, a classification of the vegetation in the vicinity of the Antarctic Peninsula, based primarily on physiognomic criteria has recently been proposed. Environmental studies have been concentrated on descriptions of the microclimatic conditions occurring at plant level and have revealed aspects of the widely fluctuating conditions which prevail in the summer, in contrast to the remarkably uniform conditions that exist under the winter snow blanket. Studies on water availability in Antarctic mosses have also been reviewed. The experimental autecological work to date, has been concerned with the effects of microclimate on the growth and reproductive behaviour of various mosses as well as the two native Antarctic flowering plants, and attempts have been made to interpret the data from field studies by growing representatives of the field populations under controlled conditions in a phytotron
Coexistence of Antiferromagnetism and Superconductivity in Electron-doped High-Tc Superconductors
We present magnetotransport evidence for antiferromagnetism in films of the
electron-doped cuprates PrCeCuO. Our results show clear
signature of static antiferromagnetism up to optimal doping x=0.15, with a
quantum phase transition close to x=0.16, and a coexistence of static
antiferromagnetism and superconductivity for 0.12x0.15
Radio Emission from the Intermediate-mass Black Hole in the Globular Cluster G1
We have used the Very Large Array (VLA) to search for radio emission from the
globular cluster G1 (Mayall-II) in M31. G1 has been reported by Gebhardt et al.
to contain an intermediate-mass black hole (IMBH) with a mass of ~2 x 10^4
solar masses. Radio emission was detected within an arcsecond of the cluster
center with an 8.4 GHz power of 2 x 10^{15} W/Hz. The radio/X-ray ratio of G1
is a few hundred times higher than that expected for a high-mass X-ray binary
in the cluster center, but is consistent with the expected value for accretion
onto an IMBH with the reported mass. A pulsar wind nebula is also a possible
candidate for the radio and X-ray emission from G1; future high-sensitivity
VLBI observations might distinguish between this possibility and an IMBH. If
the radio source is an IMBH, and similar accretion and outflow processes occur
for hypothesized ~ 1000-solar-mass black holes in Milky Way globular clusters,
they are within reach of the current VLA and should be detectable easily by the
Expanded VLA when it comes on line in 2010.Comment: ApJ Letters, accepted, 11 pages, 1 figur
- …