365,610 research outputs found
Shock wave velocity and shock pressure for low density powders: A novel approach
A novel approach is presented to predict the shock wave velocity as well as the shock wave pressure in powder materials. It is shown that the influence of the specific volume behind the shock wave on shock wave velocity and shock pressure decreases with decreasing initial powder density. The new model is compared with experimental data of various materials: Fe, Cu, Al, C, UO2, Ce2O3, SiO2 (quartz), NaCl, and polystyrene. It is concluded that the model holds in particular for initial powder densities less than 50% and for flyer plate velocities up to 5 km/s.
Free radical formation during machining and fracture of polymers
Electron paramagnetic resonance measurements of free radical formation during cutting and grinding of polymer
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An Investigation into the Effect of the Shell on SALM Processed Parts
Shell Assisted Layer Manufacturing (SALM) is a novel process for rapid prototyping/
tooling/ manufacture (RP/RT/RM) which is presently undergoing feasibility studies. SALM is
based on layered manufacturing technology (LMT). Initially it develops the shell (boundaries)
of a selected layer using a technique similar to fused deposition modelling (FDM). The
developed shell is filled with a UV curable resin and is exposed to UV radiation for curing.
This procedure is repeated until the complete part is built. This paper compares and contrasts
properties of parts made using two options available with the SALM technique: building the
part using a soluble shell (FDM support structure material, finally dissolved to recover the
part); or using a polymer material such as ABS that is bonded with the resin whilst making
the part.Mechanical Engineerin
Prototyping Virtual Data Technologies in ATLAS Data Challenge 1 Production
For efficiency of the large production tasks distributed worldwide, it is
essential to provide shared production management tools comprised of
integratable and interoperable services. To enhance the ATLAS DC1 production
toolkit, we introduced and tested a Virtual Data services component. For each
major data transformation step identified in the ATLAS data processing pipeline
(event generation, detector simulation, background pile-up and digitization,
etc) the Virtual Data Cookbook (VDC) catalogue encapsulates the specific data
transformation knowledge and the validated parameters settings that must be
provided before the data transformation invocation. To provide for local-remote
transparency during DC1 production, the VDC database server delivered in a
controlled way both the validated production parameters and the templated
production recipes for thousands of the event generation and detector
simulation jobs around the world, simplifying the production management
solutions.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 5 pages, 3 figures, pdf. PSN TUCP01
Nuclear condensation and the equation of state of nuclear matter
The isothermal compression of a dilute nucleonic gas invoking cluster degrees
of freedom is studied in an equilibrium statistical model; this clusterized
system is found to be more stable than the pure nucleonic system. The equation
of state (EoS) of this matter shows features qualitatively very similar to the
one obtained from pure nucleonic gas. In the isothermal compression process,
there is a sudden enhancement of clusterization at a transition density
rendering features analogous to the gas-liquid phase transition in normal
dilute nucleonic matter. Different observables like the caloric curves, heat
capacity, isospin distillation, etc. are studied in both the models. Possible
changes in the observables due to recently indicated medium modifications in
the symmetry energy are also investigated.Comment: 18 pages and 11 figures. Phys. Rev. C (in press
Orientational correlations and the effect of spatial gradients in the equilibrium steady state of hard rods in 2D : A study using deposition-evaporation kinetics
Deposition and evaporation of infinitely thin hard rods (needles) is studied
in two dimensions using Monte Carlo simulations. The ratio of deposition to
evaporation rates controls the equilibrium density of rods, and increasing it
leads to an entropy-driven transition to a nematic phase in which both static
and dynamical orientational correlation functions decay as power laws, with
exponents varying continuously with deposition-evaporation rate ratio. Our
results for the onset of the power-law phase agree with those for a conserved
number of rods. At a coarse-grained level, the dynamics of the non-conserved
angle field is described by the Edwards-Wilkinson equation. Predicted relations
between the exponents of the quadrupolar and octupolar correlation functions
are borne out by our numerical results. We explore the effects of spatial
inhomogeneity in the deposition-evaporation ratio by simulations, entropy-based
arguments and a study of the new terms introduced in the free energy. The
primary effect is that needles tend to align along the local spatial gradient
of the ratio. A uniform gradient thus induces a uniformly aligned state, as
does a gradient which varies randomly in magnitude and sign, but acts only in
one direction. Random variations of deposition-evaporation rates in both
directions induce frustration, resulting in a state with glassy
characteristics.Comment: modified version, Accepted for publication in Physical Review
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