The idea behind hyper-heuristics is to discover some combination of straightforward heuristics to solve a wide range of problems. To be worthwhile, such a combination should outperform the single ...heuristics. This article presents a GA-based method that produces general hyper-heuristics that solve two-dimensional regular (rectangular) and irregular (convex polygonal) bin-packing problems. A hyper-heuristic is used to define a high-level heuristic that controls low-level heuristics. The hyper-heuristic should decide when and where to apply each single low-level heuristic, depending on the given problem state. In this investigation two kinds of heuristics were considered: for selecting the figures (pieces) and objects (bins), and for placing the figures into the objects. Some of the heuristics were taken from the literature, others were adapted, and some other variations developed by us. We chose the most representative heuristics of their type, considering their individual performance in various studies and also in an initial experimentation on a collection of benchmark problems. The GA included in the proposed model uses a variable-length representation, which evolves combinations of condition-action rules producing hyper-heuristics after going through a learning process which includes training and testing phases. Such hyper-heuristics, when tested with a large set of benchmark problems, produce outstanding results for most of the cases. The testbed is composed of problems used in other similar studies in the literature. Some additional instances for the testbed were randomly generated.
A double Roman dominating function (DRDF) on a graph
G
=
(
V
,
E
)
is a function
f
:
V
→
{
0
,
1
,
2
,
3
}
satisfying (i) if
f
(
v
)
=
0
, then there must be at least two neighbors assigned 2 under
f
...or one neighbor
w
with
f
(
w
)
=
3
; and (ii) if
f
(
v
)
=
1
then
v
must be adjacent to a vertex
w
, such that
f
(
w
)
≥
2
. A DRDF is an outer independent total double Roman dominating function (OITDRDF) on
G
if the set of vertices labeled 0 induces an edgeless subgraph and the subgraph induced by the vertices with a non-zero label has no isolated vertices. The weight of an OITDRDF is the sum of its function values over all vertices, and the outer independent total Roman dominating number
γ
tdR
oi
(
G
)
is the minimum weight of an OITDRDF on
G
. First, we show that the problem of determining
γ
tdR
oi
(
G
)
is NP-complete for bipartite and chordal graphs. Then, we show that it is solvable in linear time when we are restricting to bounded clique-width graphs. Moreover, we present some tight bounds on
γ
tdR
oi
(
G
)
as well as the exact values for several graph families.
Based on the history that the Emperor Constantine decreed that any undefended place (with no legions) of the Roman Empire must be protected by a “stronger” neighbor place (having two legions), a ...graph theoretical model called Roman domination in graphs was described. A Roman dominating function for a graph G=(V,E), is a function f:V→{0,1,2} such that every vertex v with f(v)=0 has at least a neighbor w in G for which f(w)=2. The Roman domination number of a graph is the minimum weight, ∑v∈Vf(v), of a Roman dominating function. In this paper we initiate the study of a new parameter related to Roman domination, which we call strong Roman domination number and denote it by γStR(G). We approach the problem of a Roman domination-type defensive strategy under multiple simultaneous attacks and begin with the study of several mathematical properties of this invariant. In particular, we first show that the decision problem regarding the computation of the strong Roman domination number is NP-complete, even when restricted to bipartite graphs. We obtain several bounds on such a parameter and give some realizability results for it. Moreover, we prove that for any tree T of order n≥3, γStR(T)≤6n/7 and characterize all extremal trees.
The General Image Quality Equation (GIQE) is an analytical tool derived by regression modelling that is routinely employed to gauge the interpretability of raw and processed images, computing the ...most popular quantitative metric to evaluate image quality; the National Image Interpretability Rating Scale (NIIRS). There are three known versions of this equation; GIQE 3, GIQE 4 and GIQE 5, but the last one is scarcely known. The variety of versions, their subtleties, discontinuities and incongruences, generate confusion and problems among users. The first objective of this paper is to identify typical sources of confusion in the use of the GIQE, suggesting novel solutions to the main problems found in its application and presenting the derivation of a continuous form of GIQE 4, denominated GIQE 4C, that provides better correlation with GIQE 3 and GIQE 5. The second objective of this paper is to compare the predictions of GIQE 4C and GIQE 5, regarding the maximum image quality rating that can be achieved by image processing techniques. It is concluded that the transition from GIQE 4 to GIQE 5 is a major paradigm shift in image quality metrics, because it reduces the benefit of image processing techniques and enhances the importance of the raw image and its signal to noise ratio.
The two rings of (50000) Quaoar Pereira, C. L.; Sicardy, B.; Morgado, B. E. ...
Astronomy and astrophysics (Berlin),
05/2023, Letnik:
673
Journal Article
Recenzirano
Odprti dostop
Context.
Quaoar is a classical trans-Neptunian object (TNO) with an area-equivalent diameter of 1100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations ...observed between 2018 and 2021, an inhomogeneous ring (Q1R, i.e., Quaoar’s first ring) has been detected around this body.
Aims.
A new stellar occultation by Quaoar was observed on August 9, 2022, with the aim of improving Quaoar’s shape models and the physical parameters of Q1R, while searching for additional material around the body.
Methods.
The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements).
Results.
Quaoar’s elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of 579.5 ± 4.0 km, apparent oblateness of 0.12 ± 0.01, and area-equivalent radius of 543 ± 2 km. Quaoar’s limb orientation is consistent with Q1R and Weywot orbiting in Quaoar’s equatorial plane. The orbital radius of Q1R is refined to a value of 4057 ± 6 km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of ∼5 km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of 2520 ± 20 km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of ∼0.004. Just as Q1R, it also lies outside Quaoar’s classical Roche limit.
Social parasitism is more commonly found among the Hymenoptera. However, a recent study reported a case of parasitism between Neotropical pseudoscorpion species. Here, we extend the knowledge about ...this relationship, adding information about the species from Colombia. Sampling of Paratemnoides nidificator colonies in a secondary dry forest revealed the presence of two other species of pseudoscorpions also sharing the nest of the host. We presented data about the occurrence of Parachernes melanopygus and a second inquiline species of genus Lustrochernes (both Chernetidae) and how they affect the host species. Aspects of the species ecology and behaviour are discussed.
The staged Z-pinch (SZP) is a magnetoinertial fusion scheme, where a high-Z gas liner implodes onto a deuterium gas target. An accurate measurement of the initial mass distribution, both in the liner ...and target, is crucial to achieve the fusion-relevant conditions. This paper presents the characterization of a double-valve injector for the SZP experiment, performed on a test stand with interferometric and visible emission diagnostics. The injector produces an annular liner gas profile that is peaked at R L = 1.25 cm, has an average full width at half-maximum Δr L = 0.50 cm, and a mass density ρ L = 0.5-140 μg/cm 3 , which is adjusted by selecting the gas species between Ar and Kr, plenum pressure, and injection timing. The target gas density is centered on the axis, has a width Δr T = 0.80 cm, and a density ρ T = 0.3-30 μg/cm 3 . The molecular deuterium can be partially ionized and accelerated out of the injector with a velocity v z > 2 cm/μs by a coaxial plasma gun built into the injector.
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