1,552 research outputs found
DC Microgrid Modeling and Energy Storage Placement to Enhance System Stability
The work of this thesis represents a joint venture between the University of Wisconsin-Milwaukee and the University of Wisconsin-Madison. A DC microgrid is selected for the efficiency benefits, lack of reactive power in the system, and ease of connecting to an AC grid. The system modeling relies on physical parameters and industry standard methods for the estimation of loads and lines. An example model is created for the University of Wisconsin - Milwaukee\u27s Campus. Due to the high penetration of renewable energy sources in the example model, system stability is a concern. To help mitigate stability issues, analysis is performed to have the ideal placement of energy storage. The analysis relies heavily on the deep properties of the system such as Eigenvalues and system controllability. Energy storage placement is verified and evaluated
with model simulations
Partitioning Edge-Colored Hypergraphs into Few Monochromatic Tight Cycles
Confirming a conjecture of Gy´arf´as, we prove that, for all natural numbers k and
r, the vertices of every r-edge-colored complete k-uniform hypergraph can be partitioned into a
bounded number (independent of the size of the hypergraph) of monochromatic tight cycles. We
further prove that, for all natural numbers p and r, the vertices of every r-edge-colored complete
graph can be partitioned into a bounded number of pth powers of cycles, settling a problem of Elekes,
Soukup, Soukup, and Szentmikl´ossy [Discrete Math., 340 (2017), pp. 2053–2069]. In fact we prove a
common generalization of both theorems which further extends these results to all host hypergraphs
of bounded independence number
Chromatic number, clique subdivisions, and the conjectures of Haj\'os and Erd\H{o}s-Fajtlowicz
For a graph , let denote its chromatic number and
denote the order of the largest clique subdivision in . Let H(n) be the
maximum of over all -vertex graphs . A famous
conjecture of Haj\'os from 1961 states that for every
graph . That is, for all positive integers . This
conjecture was disproved by Catlin in 1979. Erd\H{o}s and Fajtlowicz further
showed by considering a random graph that for some
absolute constant . In 1981 they conjectured that this bound is tight up
to a constant factor in that there is some absolute constant such that
for all -vertex graphs . In this
paper we prove the Erd\H{o}s-Fajtlowicz conjecture. The main ingredient in our
proof, which might be of independent interest, is an estimate on the order of
the largest clique subdivision which one can find in every graph on
vertices with independence number .Comment: 14 page
Quantum fingerprinting
Classical fingerprinting associates with each string a shorter string (its
fingerprint), such that, with high probability, any two distinct strings can be
distinguished by comparing their fingerprints alone. The fingerprints can be
exponentially smaller than the original strings if the parties preparing the
fingerprints share a random key, but not if they only have access to
uncorrelated random sources. In this paper we show that fingerprints consisting
of quantum information can be made exponentially smaller than the original
strings without any correlations or entanglement between the parties: we give a
scheme where the quantum fingerprints are exponentially shorter than the
original strings and we give a test that distinguishes any two unknown quantum
fingerprints with high probability. Our scheme implies an exponential
quantum/classical gap for the equality problem in the simultaneous message
passing model of communication complexity. We optimize several aspects of our
scheme.Comment: 8 pages, LaTeX, one figur
LittleDarwin: a Feature-Rich and Extensible Mutation Testing Framework for Large and Complex Java Systems
Mutation testing is a well-studied method for increasing the quality of a
test suite. We designed LittleDarwin as a mutation testing framework able to
cope with large and complex Java software systems, while still being easily
extensible with new experimental components. LittleDarwin addresses two
existing problems in the domain of mutation testing: having a tool able to work
within an industrial setting, and yet, be open to extension for cutting edge
techniques provided by academia. LittleDarwin already offers higher-order
mutation, null type mutants, mutant sampling, manual mutation, and mutant
subsumption analysis. There is no tool today available with all these features
that is able to work with typical industrial software systems.Comment: Pre-proceedings of the 7th IPM International Conference on
Fundamentals of Software Engineerin
Submonolayer Epitaxy Without A Critical Nucleus
The nucleation and growth of two--dimensional islands is studied with Monte
Carlo simulations of a pair--bond solid--on--solid model of epitaxial growth.
The conventional description of this problem in terms of a well--defined
critical island size fails because no islands are absolutely stable against
single atom detachment by thermal bond breaking. When two--bond scission is
negligible, we find that the ratio of the dimer dissociation rate to the rate
of adatom capture by dimers uniquely indexes both the island size distribution
scaling function and the dependence of the island density on the flux and the
substrate temperature. Effective pair-bond model parameters are found that
yield excellent quantitative agreement with scaling functions measured for
Fe/Fe(001).Comment: 8 pages, Postscript files (the paper and Figs. 1-3), uuencoded,
compressed and tarred. Surface Science Letters, in press
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