39,517 research outputs found
Non-elitist Evolutionary Multi-objective Optimizers Revisited
Since around 2000, it has been considered that elitist evolutionary
multi-objective optimization algorithms (EMOAs) always outperform non-elitist
EMOAs. This paper revisits the performance of non-elitist EMOAs for
bi-objective continuous optimization when using an unbounded external archive.
This paper examines the performance of EMOAs with two elitist and one
non-elitist environmental selections. The performance of EMOAs is evaluated on
the bi-objective BBOB problem suite provided by the COCO platform. In contrast
to conventional wisdom, results show that non-elitist EMOAs with particular
crossover methods perform significantly well on the bi-objective BBOB problems
with many decision variables when using the unbounded external archive. This
paper also analyzes the properties of the non-elitist selection.Comment: This is an accepted version of a paper published in the proceedings
of GECCO 201
The SiRi Particle-Telescope System
A silicon particle-telescope system for light-ion nuclear reactions is
described. In particular, the system is designed to be optimized for level
density and gamma-ray strength function measurements with the so-called Oslo
method. Eight trapezoidal modules are mounted at 5 cm distance from the target,
covering 8 forward angles between theta = 40 and 54 degrees. The thin front dE
detectors (130 micrometer) are segmented into eight pads, determining the
reaction angle for the outgoing charged ejectile. Guard rings on the thick back
E detectors (1550 micrometer) guarantee low leakage current at high depletion
voltage.Comment: 6 pages, 8 figure
Consequences of inter-population crosses on developmental stability and canalization of floral traits in Dalechampia scandens (Euphorbiaceae)
Scalar Dark Matter From Theory Space
The scalar dark matter candidate in a prototypical theory space little Higgs
model is investigated. We review all details of the model pertinent to dark
matter. We perform a thermal relic density calculation including couplings to
the gauge and Higgs sectors of the model. We find two regions of parameter
space that give acceptable dark matter abundances. The first region has a dark
matter candidate with a mass of order 100 GeV, the second region has a heavy
candidate with a mass greater than about 500 GeV$. The dark matter candidate in
either region is an admixture of an SU(2) triplet and an SU(2) singlet, thereby
constituting a WIMP (weakly interacting massive particle).Comment: 18 pages, 2 figures, version to appear in PR
On the frequency and remnants of Hypernovae
Under the hypothesis that some fraction of massive stellar core collapses
give rise to unusually energetic events, termed hypernovae, I examine the
required rates assuming some fraction of such events yield gamma ray bursts. I
then discuss evidence from studies of pulsars and r-process nucleosynthesis
that independently suggests the existence of a class of unusually energetic
events. Finally I describe a scenario which links these different lines of
evidence as supporting the hypernova hypothesis.Comment: TeX, To appear in ApJ Letter
An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars
We present a high-resolution elemental-abundance analysis for a sample of 23
very metal-poor (VMP; [Fe/H] < -2.0) stars, 12 of which are extremely
metal-poor (EMP; [Fe/H] < -3.0), and 4 of which are ultra metal-poor (UMP;
[Fe/H] < -4.0). These stars were targeted to explore differences in the
abundance ratios for elements that constrain the possible astrophysical sites
of element production, including Li, C, N, O, the alpha-elements, the iron-peak
elements, and a number of neutron-capture elements. This sample substantially
increases the number of known carbon-enhanced metal-poor (CEMP) and
nitrogen-enhanced metal-poor (NEMP) stars -- our program stars include eight
that are considered "normal" metal-poor stars, six CEMP-no stars, five CEMP-s
stars, two CEMP-r stars, and two CEMP-r/s stars. One of the CEMP- stars and
one of the CEMP-r/s stars are possible NEMP stars. We detect lithium for three
of the six CEMP-no stars, all of which are Li-depleted with respect to the
Spite plateau. The majority of the CEMP stars have [C/N] > 0. The stars with
[C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit
this signature are only found at [Fe/H] < -3.4, a metallicity below which we
also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We
confirm the existence of two plateaus in the absolute carbon abundances of CEMP
stars, as suggested by Spite et al. We also present evidence for a "floor" in
the absolute Ba abundances of CEMP-no stars at A(Ba)~ -2.0.Comment: 20 pages, 16 figures, Accepted for publication in Ap
Catch Crops in Organic Farming Systems without Livestock Husbandry - Model Simulations
During the last years, an increasing number of stockless farms in Europe converted to organic farming practice without re-establishing a livestock. Due to the lack of animal manure as a nutrient input, the relocation and the external input of nutrients is limited in those organic cropping systems. The introduction of a one-year green manure fallow in a 4-year crop rotation, including clover-grass mixtures as a green manure crop is the classical strategy to solve at least some of the problems related to the missing livestock. The development of new crop rotations, including an extended use of catch crops and annual green manure (legumes) may be another possibility avoiding the economical loss during the fallow year.
Modelling of the C and N turnover in the soil-plant-atmosphere system using the soil-plant-atmosphere model DAISY is one of the tools used for the development of new organic crop rotations. In this paper, we will present simulations based on a field experiment with incorporation of different catch crops.
An important factor for the development of new crop rotations for stockless organic farming systems is the expected N mineralisation and immobilisation after incorporation of the plant materials. Therefore, special emphasise will be put on the simulation of N-mineralisation/-immobilisation and of soil microbial biomass N. Furthermore, particulate organic matter C and N as an indicator of remaining plant material under decomposition will be investigated
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