3,430 research outputs found
SamACO: variable sampling ant colony optimization algorithm for continuous optimization
An ant colony optimization (ACO) algorithm offers
algorithmic techniques for optimization by simulating the foraging behavior of a group of ants to perform incremental solution
constructions and to realize a pheromone laying-and-following
mechanism. Although ACO is first designed for solving discrete
(combinatorial) optimization problems, the ACO procedure is
also applicable to continuous optimization. This paper presents
a new way of extending ACO to solving continuous optimization
problems by focusing on continuous variable sampling as a key
to transforming ACO from discrete optimization to continuous
optimization. The proposed SamACO algorithm consists of three
major steps, i.e., the generation of candidate variable values for
selection, the ants’ solution construction, and the pheromone
update process. The distinct characteristics of SamACO are the
cooperation of a novel sampling method for discretizing the
continuous search space and an efficient incremental solution
construction method based on the sampled values. The performance
of SamACO is tested using continuous numerical functions
with unimodal and multimodal features. Compared with some
state-of-the-art algorithms, including traditional ant-based algorithms
and representative computational intelligence algorithms
for continuous optimization, the performance of SamACO is seen
competitive and promising
Initial pattern library algorithm for human action recognition
AbstractHuman action recognition is currently one of the most active research topics in society management, including human moving detection, human moving classification, human moving tracking, and activity recognition and description. In this paper, we have proposed a new classifying and sorting initial pattern library algorithm for human action recognition. First, we classify the training vector set to two subsets by vector variance. Secondly, sort the subsets to put the similar pattern vectors together. Last, select some number of pattern vectors from the sorted subsets to form the initial pattern library. This new initial pattern library is tested by self-organizing maps (SOM) algorithm. Experimental results in image recognition show that this new initial pattern library algorithm is better than the common random sampling initial pattern library
An ant colony optimization approach for maximizing the lifetime of heterogeneous wireless sensor networks
Maximizing the lifetime of wireless sensor networks (WSNs) is a challenging problem. Although some methods exist to address the problem in homogeneous WSNs, research on this problem in heterogeneous WSNs have progressed at a slow pace. Inspired by the promising performance of ant colony optimization (ACO) to solve combinatorial problems, this paper proposes an ACO-based approach that can maximize the lifetime of heterogeneous WSNs. The methodology is based on finding the maximum number of disjoint connected covers that satisfy both sensing coverage and network connectivity. A construction graph is designed with each vertex denoting the assignment of a device in a subset. Based on pheromone and heuristic information, the ants seek an optimal path on the construction graph to maximize the number of connected covers. The pheromone serves as a metaphor for the search experiences in building connected covers. The heuristic information is used to reflect the desirability of device assignments. A local search procedure is designed to further improve the search efficiency. The proposed approach has been applied to a variety of heterogeneous WSNs. The results show that the approach is effective and efficient in finding high-quality solutions for maximizing the lifetime of heterogeneous WSNs
Open-closed field algebras
We introduce the notions of open-closed field algebra and open-closed field
algebra over a vertex operator algebra V. In the case that V satisfies certain
finiteness and reductivity conditions, we show that an open-closed field
algebra over V canonically gives an algebra over a \C-extension of the
Swiss-cheese partial operad. We also give a tensor categorical formulation and
categorical constructions of open-closed field algebras over V.Comment: 55 pages, largely revised, an old subsection is deleted, a few
references are adde
Energy Release During Slow Long Duration Flares Observed by RHESSI
Slow Long Duration Events (SLDEs) are flares characterized by long duration
of rising phase. In many such cases impulsive phase is weak with lack of
typical short-lasting pulses. Instead of that smooth, long-lasting Hard X-ray
(HXR) emission is observed. We analysed hard X-ray emission and morphology of
six selected SLDEs. In our analysis we utilized data from RHESSI and GOES
satellites. Physical parameters of HXR sources were obtained from imaging
spectroscopy and were used for the energy balance analysis. Characteristic time
of heating rate decrease, after reaching its maximum value, is very long, which
explains long rising phase of these flares.Comment: Accepted for publication in Solar Physic
Notes on contributors
The gas-phase complex UO2(TMOGA)(2)(2+) (TMOGA = tetramethyl-3-oxa-glutaramide) prepared by electrospray ionization was characterized by infrared multiphoton dissociation (IRMPD) spectroscopy. The IRMPD spectrum from 700-1800 cm(-1) was interpreted using a computational study based on density functional theory. The predicted vibrational frequencies are in good agreement with the measured values, with an average deviation of only 8 cm(-1) (<1%) and a maximum deviation of 21 cm(-1) (<2%). The only IR peak assigned to the linear uranyl moiety was the asymmetric v(3) mode, which appeared at 965 cm(-1) and was predicted by DFT as 953 cm(-1). This v(3) frequency is red-shifted relative to bare uranyl, UO22+, by ca. 150 cm(-1) due to electron donation from the TMOGA ligands. Based on the degree of red-shifting, it is inferred that two TMOGA oxygen-donor ligands have a greater effective gas basicity than the four monodentate acetone ligands in UO2(acetone)(4)(2+). The uranyl v(3) frequency was also computed for uranyl coordinated by two TMGA ligands, in which the central O-ether, of TMOGA has been replaced by CH2. The computed v(3) for UO2(TMGA)(2)(2+), 950 cm(-1), is essentially the same as that for UO2(TMOGA)(2)(2+), suggesting that electron donation to uranyl from the ether of TMOGA is minor. The computed v(3) asymmetric stretching frequencies for the three actinyl complexes, UO2(TMOGA)(2)(2+), NpO2(TMOGA)(2)(2+) and PuO2(TMOGA)(2)(2+), are comparable. This similarity is discussed in the context of the relationship between v(3) and intrinsic actinide-oxygen bond energies in actinyl complexes
New mechanism to cross the phantom divide
Recently, type Ia supernovae data appear to support a dark energy whose
equation of state crosses -1, which is a much more amazing problem than the
acceleration of the universe. We show that it is possible for the equation of
state to cross the phantom divide by a scalar field in the gravity with an
additional inverse power-law term of Ricci scalar in the Lagrangian. The
necessary and sufficient condition for a universe in which the dark energy can
cross the phantom divide is obtained. Some analytical solutions with or
are obtained. A minimal coupled scalar with different potentials,
including quadratic, cubic, quantic, exponential and logarithmic potentials are
investigated via numerical methods, respectively. All these potentials lead to
the crossing behavior. We show that it is a robust result which is hardly
dependent on the concrete form of the potential of the scalar.Comment: 11 pages, 5 figs, v3: several references added, to match the
published versio
Statistical mechanics of RNA folding: importance of alphabet size
We construct a minimalist model of RNA secondary-structure formation and use
it to study the mapping from sequence to structure. There are strong,
qualitative differences between two-letter and four or six-letter alphabets.
With only two kinds of bases, there are many alternate folding configurations,
yielding thermodynamically stable ground-states only for a small set of
structures of high designability, i.e., total number of associated sequences.
In contrast, sequences made from four bases, as found in nature, or six bases
have far fewer competing folding configurations, resulting in a much greater
average stability of the ground state.Comment: 7 figures; uses revtex
Emergency Mosquito Control on a Selected Area in Eastern North Carolina After Hurricane Irene
Natural disasters such as hurricanes may contribute to mosquito abundance and, consequently, arbovirus transmission risk. In 2011, flooding from Hurricane Irene in eastern North Carolina (NC) resulted in increased mosquito populations that hindered recovery efforts. Budget shortfalls in NC have reduced the functionality of long-term mosquito surveillance and control programs; hence, many counties rely on the Federal Emergency Management Agency for post-disaster mosquito control. This pilot study examines mosquito abundance pre- and post-aerial insecticide spraying at eight study sites in Washington and Tyrrell Counties in rural eastern NC after Hurricane Irene. Percent change was calculated and compared for traps in areas that received aerial pesticide application and those that did not. Traps in spray zones show decreases in mosquito abundance when compared to control traps (treatment: −52.93%; control: 3.55%), although no significant differences (P = 0.286) were found in mosquito abundance between groups. Implications of reactive rather than proactive mosquito control responses are discussed
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