243,527 research outputs found
Techniques for controlling warpage and residual stresses in welded structures
Thermal pattern alteration technique controls both distortion and residual stresses in aluminum weldments. Cryogenic liquids and auxiliary heat sources are used to produce contraction and expansion of metal in the vicinity of the weld in such a manner as to counterbalance expansion and contraction caused by welding
Growth and Output Fluctuations,
Output fluctuations are driven by expectations about the degree of competition in the product market (and R&D sector). We examine how the characteristics of endogenous cycles change in the long run, as labour productivity grows faster. Main results: (i) expansion (or contraction) occurs more (or less) frequently, (ii) expansion becomes milder but contraction severer, (iii) the amplitude of fluctuations becomes larger, (iv) the variance of output changes ambiguously, indicating a non-linear relation. Once the growth of labour productivity is endogenised with learning-by- doing, it grows faster in contraction if the strength of inter-industry learning spillovers is relatively weak.expectations; fluctuations; growth; learning-by-doing; innovations
The Fiber Walk: A Model of Tip-Driven Growth with Lateral Expansion
Tip-driven growth processes underlie the development of many plants. To date,
tip-driven growth processes have been modelled as an elongating path or series
of segments without taking into account lateral expansion during elongation.
Instead, models of growth often introduce an explicit thickness by expanding
the area around the completed elongated path. Modelling expansion in this way
can lead to contradictions in the physical plausibility of the resulting
surface and to uncertainty about how the object reached certain regions of
space. Here, we introduce "fiber walks" as a self-avoiding random walk model
for tip-driven growth processes that includes lateral expansion. In 2D, the
fiber walk takes place on a square lattice and the space occupied by the fiber
is modelled as a lateral contraction of the lattice. This contraction
influences the possible follow-up steps of the fiber walk. The boundary of the
area consumed by the contraction is derived as the dual of the lattice faces
adjacent to the fiber. We show that fiber walks generate fibers that have
well-defined curvatures, enable the identification of the process underlying
the occupancy of physical space. Hence, fiber walks provide a base from which
to model both the extension and expansion of physical biological objects with
finite thickness.Comment: Plos One (in press
Multilayer distortion in the reconstructed (110) surface of Au
A new LEED intensity analysis of the reconstructed Au(110)-(1×2) surface results in a modification of the missing row model with considerable distortions which are at least three layers deep. The top layer spacing is contracted by about 20%, the second layer exhibits a lateral pairing displacement of 0.07 Å and the third layer is buckled by 0.24 Å. Distortions in deeper layers seem to be probable but have not been considered in this analysis. The inter-atomic distances in the distorted surface region show both an expansion and a contraction compared to the bulk value and range from 5% contraction to about 4% expansion
Flow of a blood analogue solution through microfabricated hyperbolic contractions
The flow of a blood analogue solution past a microfabricated hyperbolic contraction followed by an abrupt expansion was investigated experimentally. The shape of the contraction was designed in order to impose a nearly constant strain rate to the fluid along the centerline of the microgeometry. The flow patterns of the blood analogue solution and of a Newtonian reference fluid (deionized water), captured using streak line imaging, are quite distinct and illustrate the complex behavior of the blood analogue solution flowing through the microgeometry. The flow of the blood analogue solution shows elastic-driven effects with vortical structures emerging upstream of the contraction, which are absent in Newtonian fluid flow. In both cases the flow also develops instabilities downstream of the expansion but these are inertia driven. Therefore, for the blood analogue solution at high flow rates the competing effects of inertia and elasticity lead to complex flow patterns and unstable flow develops
Arrow Contraction and Expansion in Tropical Diagrams
Arrow contraction applied to a tropical diagram of probability spaces is a
modification of the diagram, replacing one of the morphisms by an isomorphims,
while preserving other parts of the diagram. It is related to the rate regions
introduced by Ahlswede and K\"orner. In a companion article we use arrow
contraction to derive information about the shape of the entropic cone. Arrow
expansion is the inverse operation to the arrow contraction.Comment: 20 pages, V2 updated reference
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