1,463 research outputs found
Evolution of the Concept of Logistics
Logistics has been, is, and probably will continue to be a most controversial military subject, There is absolutely nothing wrong with controversy when it leads to better understanding, better organization, or better operations. With regard to military logistics, however, these objectives have escaped our grasp lime and time again because very few of us have ever appeared to be talking about the same thing
The Roll Away Saloon
With his animated tales of Zane Grey, Butch Cassidy, and the Robbers Roost gang, Rider creates an engaging and believable picture of the joys and hardships of cowboy life.https://digitalcommons.usu.edu/usupress_pubs/1082/thumbnail.jp
Sedimentology and kinematics of a large, retrogressive growth-fault system in Upper Carboniferous deltaic sediments, western Ireland
Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under-represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth-fault complex affects strata up to 60 m in thickness and extends laterally for 3 km. Study of this Namurian (Upper Carboniferous) growth-fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open-ended slides, and the faults display both disintegrative and non-disintegrative structure. Thin-bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth-fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults
The Roll Away Saloon
With his animated tales of Zane Grey, Butch Cassidy, and the Robbers Roost gang, Rider creates an engaging and believable picture of the joys and hardships of cowboy life
A Mathematical Theory of Stochastic Microlensing II. Random Images, Shear, and the Kac-Rice Formula
Continuing our development of a mathematical theory of stochastic
microlensing, we study the random shear and expected number of random lensed
images of different types. In particular, we characterize the first three
leading terms in the asymptotic expression of the joint probability density
function (p.d.f.) of the random shear tensor at a general point in the lens
plane due to point masses in the limit of an infinite number of stars. Up to
this order, the p.d.f. depends on the magnitude of the shear tensor, the
optical depth, and the mean number of stars through a combination of radial
position and the stars' masses. As a consequence, the p.d.f.s of the shear
components are seen to converge, in the limit of an infinite number of stars,
to shifted Cauchy distributions, which shows that the shear components have
heavy tails in that limit. The asymptotic p.d.f. of the shear magnitude in the
limit of an infinite number of stars is also presented. Extending to general
random distributions of the lenses, we employ the Kac-Rice formula and Morse
theory to deduce general formulas for the expected total number of images and
the expected number of saddle images. We further generalize these results by
considering random sources defined on a countable compact covering of the light
source plane. This is done to introduce the notion of {\it global} expected
number of positive parity images due to a general lensing map. Applying the
result to microlensing, we calculate the asymptotic global expected number of
minimum images in the limit of an infinite number of stars, where the stars are
uniformly distributed. This global expectation is bounded, while the global
expected number of images and the global expected number of saddle images
diverge as the order of the number of stars.Comment: To appear in JM
Innovation and Equality: an Approach to Constructing a Community Governed Network Commons
Networked computing affords users distinct opportunities to communicate with each other, build relationships, transact business, and create. Yet, the digital divide perpetuates existing disparities between social groups. Interventions that rely on private ownership or philanthropy often fall short. Efforts to redress these disparities require collaboration across academic disciplines and with government and private sector organizations. This paper chronicles efforts in Harlem to address this through a collaborative approach to networked computing. We draw on two concepts--responsible innovation and co-governance--to sketch a community-based approach to networked computing. Second, the article identifies two potential systems, based in property law, through which a cross-section of community stakeholders could govern this networked computing infrastructure. In the end, this article seeks to integrate aspects of co-design and responsible innovation and reflects upon building bridges between researchers across academic disciplines, as well as the opportunities and difficulties of partnering with entrepreneurs and civic leaders
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The Littlewood-Gowers problem
We show that if A is a subset of Z/pZ (p a prime) of density bounded away
from 0 and 1 then the A(Z/pZ)-norm (that is the l^1-norm of the Fourier
transform) of the characterstic function of A is bounded below by an absolute
constant times (log p)^{1/2 - \epsilon} as p tends to infinity. This improves
on the exponent 1/3 in recent work of Green and Konyagin.Comment: 31 pp. Corrected typos. Updated references
Large droplet impact on water layers
The impact of large droplets onto an otherwise undisturbed layer of water is considered. The work, which is motivated primarily with regard to aircraft icing, is to try and help understand the role of splashing on the formation of ice on a wing, in particular for large droplets where splash appears, to have a significant effect. Analytical and numerical approaches are used to investigate a single droplet impact onto a water layer. The flow for small times after impact is determined analytically, for both direct and oblique impacts. The impact is also examined numerically using the volume of fluid (VOF) method. At small times there are promising comparisons between the numerical results, the analytical solution and experimental work capturing the ejector sheet. At larger times there is qualitative agreement with experiments and related simulations. Various cases are considered, varying the droplet size to layer depth ratio, including surface roughness, droplet distortion and air effects. The amount of fluid splashed by such an impact is examined and is found to increase with droplet size and to be significantly influenced by surface roughness. The makeup of the splash is also considered, tracking the incoming fluid, and the splash is found to consist mostly of fluid originating in the layer
Measurement and Compensation of Horizontal Crabbing at the Cornell Electron Storage Ring Test Accelerator
In storage rings, horizontal dispersion in the rf cavities introduces
horizontal-longitudinal (xz) coupling, contributing to beam tilt in the xz
plane. This coupling can be characterized by a "crabbing" dispersion term
{\zeta}a that appears in the normal mode decomposition of the 1-turn transfer
matrix. {\zeta}a is proportional to the rf cavity voltage and the horizontal
dispersion in the cavity. We report experiments at the Cornell Electron Storage
Ring Test Accelerator (CesrTA) where xz coupling was explored using three
lattices with distinct crabbing properties. We characterize the xz coupling for
each case by measuring the horizontal projection of the beam with a beam size
monitor. The three lattice configurations correspond to a) 16 mrad xz tilt at
the beam size monitor source point, b) compensation of the {\zeta}a introduced
by one of two pairs of RF cavities with the second, and c) zero dispersion in
RF cavities, eliminating {\zeta}a entirely. Additionally, intrabeam scattering
(IBS) is evident in our measurements of beam size vs. rf voltage.Comment: 5 figures, 10 page
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