2,669 research outputs found
A digital imaging photometry system for cometary data acquisition
This report describes a digital imaging photometry system developed in the Space Science Laboratory at the Marshall Space Flight center. The photometric system used for cometary data acquisition is based on an intensified secondary electron conduction (ISEC) vidicon coupled to a versatile data acquisition system which allows real-time interactive operation. Field tests on the Orion and Rosette nebulas indicate a limiting magnitude of approximately m sub v = 14 over the 40 arcmin field-of-view. Observations were conducted of Comet Giacobini-Zinner in August 1985. The resulting data are discussed in relation to the capabilities of the digital analysis system. The development program concluded on August 31, 1985
Experimental studies on cyclic behaviour of steel base plate connections considering anchor bolts post tensioning
This paper presents the experimental tests on cyclic behaviour of the base
plate connections that are connected to the foundation with and without fully post
tensioned anchor rods. The main aim is to evaluate these connections that are designed
with available design procedures from the low damage aspect. Also, the effect of post
tensioning on the seismic performance of this type of connection is presented. To
characterize the base plate connection damageability, each column base was designed for
a particular major inelastic deformation mode such as anchor rod yielding, yielding of the
column, or column and base plate yielding. It is shown that considered joints are not able
to be categorized as “a low damage”. Also, post tensioning of the base plate increases the
rotational stiffness of the base, and results in more ductility of the column with low axial forc
Dynamics of a lattice Universe
We find a solution to Einstein field equations for a regular toroidal lattice
of size L with equal masses M at the centre of each cell; this solution is
exact at order M/L. Such a solution is convenient to study the dynamics of an
assembly of galaxy-like objects. We find that the solution is expanding (or
contracting) in exactly the same way as the solution of a
Friedman-Lema\^itre-Robertson-Walker Universe with dust having the same average
density as our model. This points towards the absence of backreaction in a
Universe filled with an infinite number of objects, and this validates the
fluid approximation, as far as dynamics is concerned, and at the level of
approximation considered in this work.Comment: 14 pages. No figure. Accepted version for Classical and Quantum
Gravit
Effects Of Column Splice Properties On Seismic Demands In Steel Moment Frames
Dynamic inelastic response history analysis of a 2-D model of a nine storey steel frame were carried out with different column splice strengths and stiffnesses using a suite of 20 MCE level earthquake records. Splices were located every 2nd storey at one third of the storey height up from the column below. It was shown that (i) the presence of even very flexible splices increased the frame period by less than 3%, (ii) flexible splices increased storey drift ratios by up to 27%, (iii) splice stiffnesses of zero to infinity had no effect on frame displacements, (iv) the splice moment demand increased with increasing splice stiffness on the frame and was as high as 99% of the column flexural capacity
Experimental investigation of the shearing resistance of SODA-Lime glass at pressures of 9 GPa and strain rates of 10^6 s^(-1)
Pressure-Shear Plate Impact (PSPI) experiments were conducted to measure the high-rate shearing resistance of soda-lime glass at pressures of 9 GPa and at shearing rates of approximately 10^6 s^(−1). Samples of soda lime glass, 5 µm thick, were sandwiched between pure tungsten carbide (WC) plates and impacted by pure WC flyers. Impacting plates were inclined to the direction of approach by an angle of 18°. Normal stress and shearing resistance of the sample were calculated from measured free surface velocities using 1D elastic wave theory. The experimental results show that, at a pressure of 9GPa, the shear stress increases almost linearly up to 1 GPa and then falls quickly to approximately 0.3 GPa — after which it decreases slowly to approximately 0.17 GPa. Comparisons with results of previous experiments on nominally identical samples, impacted to generate lower peak pressures, showed the peak shearing resistance to be much higher at higher pressures; however, the sharp fall in shearing resistance occurs at comparable shear strains (1.5-2)
Experimental investigation of the shearing resistance of SODA-Lime glass at pressures of 9 GPa and strain rates of 10^6 s^(-1)
Pressure-Shear Plate Impact (PSPI) experiments were conducted to measure the high-rate shearing resistance of soda-lime glass at pressures of 9 GPa and at shearing rates of approximately 10^6 s^(−1). Samples of soda lime glass, 5 µm thick, were sandwiched between pure tungsten carbide (WC) plates and impacted by pure WC flyers. Impacting plates were inclined to the direction of approach by an angle of 18°. Normal stress and shearing resistance of the sample were calculated from measured free surface velocities using 1D elastic wave theory. The experimental results show that, at a pressure of 9GPa, the shear stress increases almost linearly up to 1 GPa and then falls quickly to approximately 0.3 GPa — after which it decreases slowly to approximately 0.17 GPa. Comparisons with results of previous experiments on nominally identical samples, impacted to generate lower peak pressures, showed the peak shearing resistance to be much higher at higher pressures; however, the sharp fall in shearing resistance occurs at comparable shear strains (1.5-2)
Classical Duals, Legendre Transforms and the Vainshtein Mechanism
We show how to generalize the classical duals found by Gabadadze {\it et al}
to a very large class of self-interacting theories. This enables one to adopt a
perturbative description beyond the scale at which classical perturbation
theory breaks down in the original theory. This is particularly relevant if we
want to test modified gravity scenarios that exhibit Vainshtein screening on
solar system scales. We recognise the duals as being related to the Legendre
transform of the original Lagrangian, and present a practical method for
finding the dual in general; our methods can also be applied to
self-interacting theories with a hierarchy of strong coupling scales, and with
multiple fields. We find the classical dual of the full quintic galileon theory
as an example.Comment: 16 page
Cytomegalovirus-associated pulmonary exacerbation in patients with cystic fibrosis.
CMV is an unusual cause of pulmonary exacerbation in immunocompetent individuals with CF http://ow.ly/Rdds30hlnjV
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