2,394 research outputs found
Generalized gamma approximation with rates for urns, walks and trees
We study a new class of time inhomogeneous P\'olya-type urn schemes and give
optimal rates of convergence for the distribution of the properly scaled number
of balls of a given color to nearly the full class of generalized gamma
distributions with integer parameters, a class which includes the Rayleigh,
half-normal and gamma distributions. Our main tool is Stein's method combined
with characterizing the generalized gamma limiting distributions as fixed
points of distributional transformations related to the equilibrium
distributional transformation from renewal theory. We identify special cases of
these urn models in recursive constructions of random walk paths and trees,
yielding rates of convergence for local time and height statistics of simple
random walk paths, as well as for the size of random subtrees of uniformly
random binary and plane trees.Comment: Published at http://dx.doi.org/10.1214/15-AOP1010 in the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Total variation error bounds for geometric approximation
We develop a new formulation of Stein's method to obtain computable upper
bounds on the total variation distance between the geometric distribution and a
distribution of interest. Our framework reduces the problem to the construction
of a coupling between the original distribution and the "discrete equilibrium"
distribution from renewal theory. We illustrate the approach in four
non-trivial examples: the geometric sum of independent, non-negative,
integer-valued random variables having common mean, the generation size of the
critical Galton-Watson process conditioned on non-extinction, the in-degree of
a randomly chosen node in the uniform attachment random graph model and the
total degree of both a fixed and randomly chosen node in the preferential
attachment random graph model.Comment: Published in at http://dx.doi.org/10.3150/11-BEJ406 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Production and characterization of Al-BN composite materials using by powder metallurgy
ArticleAluminum matrix composites containing 3,
6,
9,
12 and15%
BN has been fabricated
by conventional microwave sintering at 550
°C temperature. Compounds formation between Al
and BN powders is observed after sintering under Ar shroud. XRD, SEM (Scanning Electron
Microscope), mechanical testing and measurements were employed to characterize the properties
of Al
+
BN composite. Exper
imental results suggest that the best properties as hardness 42,
62
HV were obtained for Al+12% BN composite
Endovascular Cure of a Locked-In Patient
We report the case of a 60 year-old right-handed gentleman who became acutely “Locked-In” several days after a lower extremity orthopedic procedure. He underwent emergent endovascular treatment and had complete resolution of his neurologic findings except for mild dysarthria and dysphagia. Endovascular intervention for posterior circulation thrombosis is highly effective when patients are treated within 24 hours
Nonequilibrium phase transitions and stationary state solutions of a three-dimensional random-field Ising model under a time dependent periodic external field
Nonequilibrium behavior and dynamic phase transition properties of a kinetic
Ising model under the influence of periodically oscillating random-fields have
been analyzed within the framework of effective field theory (EFT) based on a
decoupling approximation (DA). Dynamic equation of motion has been solved for a
simple cubic lattice () by utilizing a Glauber type stochastic process.
Amplitude of the sinusoidally oscillating magnetic field is randomly
distributed on the lattice sites according to bimodal and trimodal distribution
functions. For a bimodal type of amplitude distribution, it is found in the
high frequency regime that the dynamic phase diagrams of the system in
temperature versus field amplitude plane resemble the corresponding phase
diagrams of pure kinetic Ising model. Our numerical results indicate that for a
bimodal distribution, both in the low and high frequency regimes, the dynamic
phase diagrams always exhibit a coexistence region in which the stationary
state (ferro or para) of the system is completely dependent on the initial
conditions whereas for a trimodal distribution, coexistence region disappears
depending on the values of system parameters.Comment: 11 pages, 11 figure
Digitizing Products Towards Platforms: The Case of Vehicle Motion System
The development of digital product platforms is a prevailing trend in many industries. As firms incorporate digital technologies into established product categories, they need to manage tensions on multiple organizational layers including strategy, technology and structure. Recent findings suggest that tensions are most likely to be managed by creating resource and coordination flexibility. This paper reports a longitudinal case study of developing a digital product platform. By drawing on organizational ambidexterity theory, we identify four mechanisms—re-scripting, centralizing-re-directing and decoupling—through which the firm creates resource and coordination flexibility. The resulting resource and coordination flexibility in turn lead to the transformation of the firm’s strategy, technology and internal structure. The contribution of this study is in adopting an internal perspective and a bottom-up approach which help to theorize the evolution of digitized products into digital product platforms in an emergent way
Performance of Preload on Cohesionless Soils
Common occurrence of loose normally consolidated fine sands and silts extending to considerable depths necessitates the utilization of ground improvement techniques along the coasts of Arabian Peninsula. In the case considered, the soil profile consisted of twenty meter thick compressible sands, and preloading technique was suggested to stabilize the foundation soil. The paper presents the performance of the preloading and the level of soil improvement achieved. The observed settlements and settlement-time behaviour are compared with the values estimated from various methods. The soil parameters back calculated from measured field behaviour are reported
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