1,723 research outputs found
A Flexible Methodology to Sectorize Water Supply Networks Based on Social Network Theory Concepts and on Multi-objective Optimization
A novel methodology to sectorize water supply networks (WSNs) depending on a main transmission
line is presented in this paper. The methodology is based on concepts derived from the social
network theory and graph theory (namely, community detection and shortest path respectively); and
also on a multi-objective optimization process by means of agent swarm optimization (ASO). A series
of energy, operative, and economic criteria are optimized in this process. The core idea is to form
sectors over the distribution network based on communities found using a community detection
algorithm (Walktrap). The methodology is flexible and enables the technical staff in water utilities to
make decisions at different stages. It has been tested by generating four feasible solutions over a
portion of a real WSN.Campbell-Gonzalez, E.; Izquierdo Sebastián, J.; Montalvo Arango, I.; Ilaya-Ayza, AE.; Pérez García, R.; Tavera, M. (2016). A Flexible Methodology to Sectorize Water Supply Networks Based on Social Network Theory Concepts and on Multi-objective Optimization. Journal of Hydroinformatics. 18(1):62-76. doi:10.2166/hydro.2015.146S627618
Safe and complete contig assembly via omnitigs
Contig assembly is the first stage that most assemblers solve when
reconstructing a genome from a set of reads. Its output consists of contigs --
a set of strings that are promised to appear in any genome that could have
generated the reads. From the introduction of contigs 20 years ago, assemblers
have tried to obtain longer and longer contigs, but the following question was
never solved: given a genome graph (e.g. a de Bruijn, or a string graph),
what are all the strings that can be safely reported from as contigs? In
this paper we finally answer this question, and also give a polynomial time
algorithm to find them. Our experiments show that these strings, which we call
omnitigs, are 66% to 82% longer on average than the popular unitigs, and 29% of
dbSNP locations have more neighbors in omnitigs than in unitigs.Comment: Full version of the paper in the proceedings of RECOMB 201
Adaptive Probabilistic Flooding for Multipath Routing
In this work, we develop a distributed source routing algorithm for topology
discovery suitable for ISP transport networks, that is however inspired by
opportunistic algorithms used in ad hoc wireless networks. We propose a
plug-and-play control plane, able to find multiple paths toward the same
destination, and introduce a novel algorithm, called adaptive probabilistic
flooding, to achieve this goal. By keeping a small amount of state in routers
taking part in the discovery process, our technique significantly limits the
amount of control messages exchanged with flooding -- and, at the same time, it
only minimally affects the quality of the discovered multiple path with respect
to the optimal solution. Simple analytical bounds, confirmed by results
gathered with extensive simulation on four realistic topologies, show our
approach to be of high practical interest.Comment: 6 pages, 6 figure
The Virtual Block Interface: A Flexible Alternative to the Conventional Virtual Memory Framework
Computers continue to diversify with respect to system designs, emerging
memory technologies, and application memory demands. Unfortunately, continually
adapting the conventional virtual memory framework to each possible system
configuration is challenging, and often results in performance loss or requires
non-trivial workarounds. To address these challenges, we propose a new virtual
memory framework, the Virtual Block Interface (VBI). We design VBI based on the
key idea that delegating memory management duties to hardware can reduce the
overheads and software complexity associated with virtual memory. VBI
introduces a set of variable-sized virtual blocks (VBs) to applications. Each
VB is a contiguous region of the globally-visible VBI address space, and an
application can allocate each semantically meaningful unit of information
(e.g., a data structure) in a separate VB. VBI decouples access protection from
memory allocation and address translation. While the OS controls which programs
have access to which VBs, dedicated hardware in the memory controller manages
the physical memory allocation and address translation of the VBs. This
approach enables several architectural optimizations to (1) efficiently and
flexibly cater to different and increasingly diverse system configurations, and
(2) eliminate key inefficiencies of conventional virtual memory. We demonstrate
the benefits of VBI with two important use cases: (1) reducing the overheads of
address translation (for both native execution and virtual machine
environments), as VBI reduces the number of translation requests and associated
memory accesses; and (2) two heterogeneous main memory architectures, where VBI
increases the effectiveness of managing fast memory regions. For both cases,
VBI significanttly improves performance over conventional virtual memory
Spartan Daily, March 4, 1954
Volume 42, Issue 99https://scholarworks.sjsu.edu/spartandaily/11994/thumbnail.jp
Directed nonabelian sandpile models on trees
We define two general classes of nonabelian sandpile models on directed trees
(or arborescences) as models of nonequilibrium statistical phenomena. These
models have the property that sand grains can enter only through specified
reservoirs, unlike the well-known abelian sandpile model.
In the Trickle-down sandpile model, sand grains are allowed to move one at a
time. For this model, we show that the stationary distribution is of product
form. In the Landslide sandpile model, all the grains at a vertex topple at
once, and here we prove formulas for all eigenvalues, their multiplicities, and
the rate of convergence to stationarity. The proofs use wreath products and the
representation theory of monoids.Comment: 43 pages, 5 figures; introduction improve
Deep Acrostics
Acronyms use the first letter of each word of a name. Diacronyms instead use the first two letters of names. While not yet called that, they featured in Short People in the November issue. Diacrostics are diacronyms of whole sentences. Unlike aconyms, which usually have to be defined and memorised, diacrostics may be -- and triacrostics often are -- directly readable, especially if the context is known, the language is simple, or the sentence is a familiar quotation
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