26,599 research outputs found
Two-Dimensional Scaling Limits via Marked Nonsimple Loops
We postulate the existence of a natural Poissonian marking of the double
(touching) points of SLE(6) and hence of the related continuum nonsimple loop
process that describes macroscopic cluster boundaries in 2D critical
percolation. We explain how these marked loops should yield continuum versions
of near-critical percolation, dynamical percolation, minimal spanning trees and
related plane filling curves, and invasion percolation. We show that this
yields for some of the continuum objects a conformal covariance property that
generalizes the conformal invariance of critical systems. It is an open problem
to rigorously construct the continuum objects and to prove that they are indeed
the scaling limits of the corresponding lattice objects.Comment: 25 pages, 5 figure
Real eigenvalue analysis in NASTRAN by the tridiagonal reduction (FEER) method
Implementation of the tridiagonal reduction method for real eigenvalue extraction in structural vibration and buckling problems is described. The basic concepts underlying the method are summarized and special features, such as the computation of error bounds and default modes of operation are discussed. In addition, the new user information and error messages and optional diagnostic output relating to the tridiagonal reduction method are presented. Some numerical results and initial experiences relating to usage in the NASTRAN environment are provided, including comparisons with other existing NASTRAN eigenvalue methods
The design and development of transonic multistage compressors
The development of the transonic multistage compressor is reviewed. Changing trends in design and performance parameters are noted. These changes are related to advances in compressor aerodynamics, computational fluid mechanics and other enabling technologies. The parameters normally given to the designer and those that need to be established during the design process are identified. Criteria and procedures used in the selection of these parameters are presented. The selection of tip speed, aerodynamic loading, flowpath geometry, incidence and deviation angles, blade/vane geometry, blade/vane solidity, stage reaction, aerodynamic blockage, inlet flow per unit annulus area, stage/overall velocity ratio, and aerodynamic losses are considered. Trends in these parameters both spanwise and axially through the machine are highlighted. The effects of flow mixing and methods for accounting for the mixing in the design process are discussed
Fast Community Identification by Hierarchical Growth
A new method for community identification is proposed which is founded on the
analysis of successive neighborhoods, reached through hierarchical growth from
a starting vertex, and on the definition of communities as a subgraph whose
number of inner connections is larger than outer connections. In order to
determine the precision and speed of the method, it is compared with one of the
most popular community identification approaches, namely Girvan and Newman's
algorithm. Although the hierarchical growth method is not as precise as Girvan
and Newman's method, it is potentially faster than most community finding
algorithms.Comment: 6 pages, 5 figure
Localization properties of a tight-binding electronic model on the Apollonian network
An investigation on the properties of electronic states of a tight-binding
Hamiltonian on the Apollonian network is presented. This structure, which is
defined based on the Apollonian packing problem, has been explored both as a
complex network, and as a substrate, on the top of which physical models can
defined. The Schrodinger equation of the model, which includes only nearest
neighbor interactions, is written in a matrix formulation. In the uniform case,
the resulting Hamiltonian is proportional to the adjacency matrix of the
Apollonian network. The characterization of the electronic eigenstates is based
on the properties of the spectrum, which is characterized by a very large
degeneracy. The rotation symmetry of the network and large number of
equivalent sites are reflected in all eigenstates, which are classified
according to their parity. Extended and localized states are identified by
evaluating the participation rate. Results for other two non-uniform models on
the Apollonian network are also presented. In one case, interaction is
considered to be dependent of the node degree, while in the other one, random
on-site energies are considered.Comment: 7pages, 7 figure
The National School Lunch Program: Background, Trends, and Issues
The National School Lunch Program (NSLP) is the Nation’s second largest food and nutrition assistance program. In 2006, it operated in over 101,000 public and nonprofit private schools and provided over 28 million low-cost or free lunches to children on a typical school day at a Federal cost of $8 billion for the year. This report provides background information on the NSLP, including historical trends and participant characteristics. It also addresses steps being taken to meet challenges facing administrators of the program, including tradeoffs between nutritional quality of foods served, costs, and participation, as well as between program access and program integrity.National School Lunch Program, child nutrition, obesity, food assistance, Agricultural and Food Policy, Health Economics and Policy, Public Economics,
Interfaces (and Regional Congruence?) in Spin Glasses
We present a general theorem restricting properties of interfaces between
thermodynamic states and apply it to the spin glass excitations observed
numerically by Krzakala-Martin and Palassini-Young in spatial dimensions d=3
and 4. We show that such excitations, with interface dimension smaller than d,
cannot yield regionally congruent thermodynamic states. More generally, zero
density interfaces of translation-covariant excitations cannot be pinned (by
the disorder) in any d but rather must deflect to infinity in the thermodynamic
limit. Additional consequences concerning regional congruence in spin glasses
and other systems are discussed.Comment: 4 pages (ReVTeX); 1 figure; submitted to Physical Review Letter
Probabilistic Approach to Time-Dependent Load-Transfer Models of Fracture
A probabilistic method for solving time-dependent load-transfer models of
fracture is developed. It is applicable to any rule of load redistribution,
i.e, local, hierarchical, etc. In the new method, the fluctuations are
generated during the breaking process (annealed randomness) while in the usual
method, the random lifetimes are fixed at the beginning (quenched disorder).
Both approaches are equivalent.Comment: 13 pages, 4 figures. To appear in Phys.Rev.
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