1,230 research outputs found
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Impact Absorbent Rapid Manufactured Structures (IARMS)
Rapid Manufacturing (RM) is increasingly becoming a viable manufacturing process due
to dramatic advantages that it facilitates in the area of design complexity. Through the
exploration of the design freedom afforded by RM, this paper introduces the concept and initial
research surrounding Impact Absorbent Rapid Manufactured Structures (IARMS), with an
application in sports personal protective equipment (PPE). Designs are based on the cellular
structure of foams; the inherent advantages of the cellular structure are used as a basis to create
IARMS that have the potential to be optimised for a specific impact absorbent response. The
paper provides some initial results from compression testingMechanical Engineerin
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Design Optimization Strategy for Multifunctional 3D Printing
An optimization based design methodology for the additive manufacture of multifunctional parts (for example, a structure with embedded electronic/electrical systems and
associated conductive paths) is presented. This work introduces a coupled optimization strategy
where Topology Optimization (TO) is combined with an automated placement and routing
approach that enables determination of an efficient internal system configuration. This permits
the effect of the incorporation of the internal system on the structural response of the part to be
taken into account and therefore enables the overall optimization of the structure-system unit. An
example test case is included in the paper to evaluate the optimization strategy and demonstrate
the methods effectiveness. The capability of this method allows the exploitation of the
manufacturing capability under development within the Additive Manufacturing (AM)
community to produce 3D internal systems within complex structures.Mechanical Engineerin
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An Optimization Based Design Framework for Multi-Functional 3D Printing
This work investigates design analysis and optimization methods for the integration of
active internal systems into a component for manufacture using multi-material 3D printing
processes. This enables efficient design of optimal multifunctional components that exploit the
design freedoms of additive manufacturing (AM). The main contributions of this paper are in two
areas: 1) the automated placement and routing of electrical systems within the component volume
and, 2) the accommodation of the effect of this system integration on the structural response of
the part through structural topology optimization (TO). A novel voxel modeling approach was
used to facilitate design flexibility and to allow direct mapping to the 3D printer jetting nozzles.Mechanical Engineerin
DESIGN AND HIGH POWER TESTING OF 52.809 MHZ RF CAVITIES FOR SLIP STACKING IN THE FERMILAB RECYCLER*
Abstract For NOvA and future experiments requiring high intensity proton beams, Fermilab is in the process of upgrading the existing accelerator complex for increased proton production. One such improvement is to reduce the Main Injector cycle time, by performing slip stacking, previously done in the Main Injector, in the now repurposed Recycler Ring. Recycler slip stacking requires two new RF cavities operating at slightly different frequencies (df = 1260Hz). These are copper, coaxial, quarter wave cavities with R/Q =13 ohms. They operate at a peak gap voltage of 150 kV with 150 kW peak drive power (60% duty factor), and are resonant at 52.809 MHz with a 10 kHz tuning range. Two have been completed and installed. The design, high power test results, and status of the cavities are presented
Status and specifications of a Project X front-end accelerator test facility at Fermilab
This paper describes the construction and operational status of an
accelerator test facility for Project X. The purpose of this facility is for
Project X component development activities that benefit from beam tests and any
development activities that require 325 MHz or 650 MHz RF power. It presently
includes an H- beam line, a 325 MHz superconducting cavity test facility, a 325
MHz (pulsed) RF power source, and a 650 MHz (CW) RF power source. The paper
also discusses some specific Project X components that will be tested in the
facility.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1
Apr 2011. New York, US
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A Hybrid Algorithm for Topology Optimization of Additive Manufactured Structures
Most topology (TO) algorithms involve the penalization of intricate structural features to eliminate manufacturing difficulties. Since additive manufacturing is less dependent on manufacturing
constraints, it becomes necessary to adapt these algorithms for AM. We propose a hybrid algorithm
consisting of an adaptive meshing strategy (AMS) and a modified form of the bidirectional evolutionary structural optimization (BESO) method. By solving a standard cantilever problem, we show
that the hybrid method offers improved performance over the standard BESO method. It is proposed
that the new method is more suitable for optimizing structures for AM in a computational efficient
manner.Mechanical Engineerin
Studies of Mass and Size Effects in Three-Dimensional Vibrofluidized Granular Mixtures
We examine the steady state properties of binary systems of driven inelastic
hard spheres. The spheres, which move under the influence of gravity, are
contained in a vertical cylinder with a vibrating base. We computed the
trajectories of the spheres using an event-driven molecular dynamics algorithm.
In the first part of the study, we chose simulation parameters that match those
of experiments performed by Wildman and Parker. Various properties computed
from the simulation including the density profile, granular temperature and
circulation pattern are in good qualitative agreement with the experiments. We
then studied the effect of varying the mass ratio and the size ratio
independently while holding the other parameters constant. The mass and size
ratio are shown to affect the distribution of the energy. The changes in the
energy distributions affect the packing fraction and temperature of each
component. The temperature of the heavier component has a non-linear dependence
on the mass of the lighter component, while the temperature of the lighter
component is approximately proportional to its mass. The temperature of both
components is inversely dependent on the size of the smaller component.Comment: 14 Pages, 12 Figures, RevTeX
On the role of the Knudsen layer in rapid granular flows
A combination of molecular-dynamics simulations, theoretical predictions, and
previous experiments are used in a two-part study to determine the role of the
Knudsen layer in rapid granular flows. First, a robust criterion for the
identification of the thickness of the Knudsen layer is established: a rapid
deterioration in Navier-Stokes-order prediction of the heat flux is found to
occur in the Knudsen layer. For (experimental) systems in which heat flux
measurements are not easily obtained, a rule-of-thumb for estimating the
Knudsen layer thickness follows, namely that such effects are evident within
2.5 (local) mean free paths of a given boundary. Second, comparisons of
simulation and experimental data with Navier-Stokes order theory are used to
provide a measure as to when Knudsen layer effects become non-negligible.
Specifically, predictions that do not account for the presence of a Knudsen
layer appear reliable for Knudsen layers collectively composing up to 20% of
the domain, whereas deterioration of such predictions becomes apparent when the
domain is fully comprised of the Knudsen layer.Comment: 9 figures, accepted to Journal of Fluid Mechanic
Accurate reporting of adherence to inhaled therapies in adults with cystic fibrosis: methods to calculate “normative adherence”
Background: Preventative inhaled treatments in cystic fibrosis will only be effective in maintaining lung health if used appropriately. An accurate adherence index should therefore reflect treatment effectiveness, but the standard method of reporting adherence, that is, as a percentage of the agreed regimen between clinicians and people with cystic fibrosis, does not account for the appropriateness of the treatment regimen. We describe two different indices of inhaled therapy adherence for adults with cystic fibrosis which take into account effectiveness, that is, “simple” and “sophisticated” normative adherence. Methods to calculate normative adherence: Denominator adjustment involves fixing a minimum appropriate value based on the recommended therapy given a person’s characteristics. For simple normative adherence, the denominator is determined by the person’s Pseudomonas status. For sophisticated normative adherence, the denominator is determined by the person’s Pseudomonas status and history of pulmonary exacerbations over the previous year. Numerator adjustment involves capping the daily maximum inhaled therapy use at 100% so that medication overuse does not artificially inflate the adherence level. Three illustrative cases: Case A is an example of inhaled therapy under prescription based on Pseudomonas status resulting in lower simple normative adherence compared to unadjusted adherence. Case B is an example of inhaled therapy under-prescription based on previous exacerbation history resulting in lower sophisticated normative adherence compared to unadjusted adherence and simple normative adherence. Case C is an example of nebulizer overuse exaggerating the magnitude of unadjusted adherence. Conclusion: Different methods of reporting adherence can result in different magnitudes of adherence. We have proposed two methods of standardizing the calculation of adherence which should better reflect treatment effectiveness. The value of these indices can be tested empirically in clinical trials in which there is careful definition of treatment regimens related to key patient characteristics, alongside accurate measurement of health outcomes
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