3,172 research outputs found
F-15 composite engine access door
This paper presents a summary of the successfully concluded phase 1 of the two-phase Design and Manufacture of Advanced Thermoplastic Structures (DMATS) program. It addresses the design, manufacture, and validation testing of a thermoplastic F-15E forward engine access door and includes lessons learned during the concurrent product and process design development phases of the program
Rainbow Connection Number and Radius
The rainbow connection number, rc(G), of a connected graph G is the minimum
number of colours needed to colour its edges, so that every pair of its
vertices is connected by at least one path in which no two edges are coloured
the same. In this note we show that for every bridgeless graph G with radius r,
rc(G) <= r(r + 2). We demonstrate that this bound is the best possible for
rc(G) as a function of r, not just for bridgeless graphs, but also for graphs
of any stronger connectivity. It may be noted that for a general 1-connected
graph G, rc(G) can be arbitrarily larger than its radius (Star graph for
instance). We further show that for every bridgeless graph G with radius r and
chordality (size of a largest induced cycle) k, rc(G) <= rk.
It is known that computing rc(G) is NP-Hard [Chakraborty et al., 2009]. Here,
we present a (r+3)-factor approximation algorithm which runs in O(nm) time and
a (d+3)-factor approximation algorithm which runs in O(dm) time to rainbow
colour any connected graph G on n vertices, with m edges, diameter d and radius
r.Comment: Revised preprint with an extra section on an approximation algorithm.
arXiv admin note: text overlap with arXiv:1101.574
Constitutive modeling for isotropic materials
The unified constitutive theories for application to typical isotropic cast nickel base supperalloys used for air-cooled turbine blades were evaluated. The specific modeling aspects evaluated were: uniaxial, monotonic, cyclic, creep, relaxation, multiaxial, notch, and thermomechanical behavior. Further development of the constitutive theories to model thermal history effects, refinement of the material test procedures, evaluation of coating effects, and verification of the models in an alternate material will be accomplished in a follow-on for this base program
Enhancing Synchrony in Chaotic Oscillators by Dynamic Relaying
In a chain of mutually coupled oscillators, the coupling threshold for
synchronization between the outermost identical oscillators decreases when a
type of impurity (in terms of parameter mismatch) is introduced in the inner
oscillator(s). The outer oscillators interact indirectly via dynamic relaying,
mediated by the inner oscillator(s). We confirm this enhancing of critical
coupling in the chaotic regimes of R\"ossler system in absence of coupling
delay and in Mackey-Glass system with delay coupling. The enhancing effect is
experimentally verified in electronic circuit of R\"ossler oscillators.Comment: 4 pages, 9 figure
A Dynamic Renormalization Group Study of Active Nematics
We carry out a systematic construction of the coarse-grained dynamical
equation of motion for the orientational order parameter for a two-dimensional
active nematic, that is a nonequilibrium steady state with uniaxial, apolar
orientational order. Using the dynamical renormalization group, we show that
the leading nonlinearities in this equation are marginally \textit{irrelevant}.
We discover a special limit of parameters in which the equation of motion for
the angle field of bears a close relation to the 2d stochastic Burgers
equation. We find nevertheless that, unlike for the Burgers problem, the
nonlinearity is marginally irrelevant even in this special limit, as a result
of of a hidden fluctuation-dissipation relation. 2d active nematics therefore
have quasi-long-range order, just like their equilibrium counterpartsComment: 31 pages 6 figure
Undergraduate Curriculum In Supply Chain Management
A proposal is presented for an undergraduate curriculum in Supply Chain Management(SCM) in a typical BBA program in an AACSB accredited Business School
Shear flow induced isotropic to nematic transition in a suspension of active filaments
We study the effects of externally applied shear flow on a model of
suspensions of motors and filaments, via the equations of active hydrodynamics
[PRL {\bf 89} (2002) 058101; {\bf 92} (2004) 118101]. In the absence of shear,
the orientationally ordered phase of {\it both} polar and apolar active
particles is always unstable at zero-wavenumber. An imposed steady shear large
enough to overcome the active stresses stabilises both apolar and moving polar
phases. Our work is relevant to {\it in vitro} studies of active filaments, the
reorientation of endothelial cells subject to shear flow and shear-induced
motility of attached cells.Comment: 8 pages, 4 figures submitted to Europhysics Letter
Global parameter identification of stochastic reaction networks from single trajectories
We consider the problem of inferring the unknown parameters of a stochastic
biochemical network model from a single measured time-course of the
concentration of some of the involved species. Such measurements are available,
e.g., from live-cell fluorescence microscopy in image-based systems biology. In
addition, fluctuation time-courses from, e.g., fluorescence correlation
spectroscopy provide additional information about the system dynamics that can
be used to more robustly infer parameters than when considering only mean
concentrations. Estimating model parameters from a single experimental
trajectory enables single-cell measurements and quantification of cell--cell
variability. We propose a novel combination of an adaptive Monte Carlo sampler,
called Gaussian Adaptation, and efficient exact stochastic simulation
algorithms that allows parameter identification from single stochastic
trajectories. We benchmark the proposed method on a linear and a non-linear
reaction network at steady state and during transient phases. In addition, we
demonstrate that the present method also provides an ellipsoidal volume
estimate of the viable part of parameter space and is able to estimate the
physical volume of the compartment in which the observed reactions take place.Comment: Article in print as a book chapter in Springer's "Advances in Systems
Biology
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