6,643 research outputs found
Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices
The exploration of topological states is of significant fundamental and
practical importance in contemporary condensed matter physics, for which the
extension to two-dimensional (2D) organometallic systems is particularly
attractive. Using first-principles calculations, we show that a 2D hexagonal
triphenyl-lead lattice composed of only main group elements is susceptible to a
magnetic instability, characterized by a considerably more stable
antiferromagnetic (AFM) insulating state rather than the topologically
nontrivial quantum spin Hall state proposed recently. Even though this AFM
phase is topologically trivial, it possesses an intricate emergent degree of
freedom, defined by the product of spin and valley indices, leading to Berry
curvature-induced spin and valley currents under electron or hole doping.
Furthermore, such a trivial band insulator can be tuned into a topologically
nontrivial matter by the application of an out-of-plane electric field, which
destroys the AFM order, favoring instead ferrimagnetic spin ordering and a
quantum anomalous Hall state with a non-zero topological invariant. These
findings further enrich our understanding of 2D hexagonal organometallic
lattices for potential applications in spintronics and valleytronics.Comment: 9 pages, 8 figure
An improved real hybrid genetic algorithm
Želeći riješiti problem prerane konvergencije genetskog algoritma i algoritma roja čestica, kako bi se omogućilo da te dvije metode konvergiraju ka globalnom optimalnom rješenju uz najveću vjerojatnoću te da se poboljša učinkovitost algoritma, u članku će se kombinirati poboljšani genetski algoritam s metodom poboljšane optimalizacije roja čestica da bi se sastavio miješani poboljšani algoritam. Uz različite referentne funkcije upotrjebljene za testiranje funkcioniranja stvarno hibridnog genetskog algoritma, rezultati pokazuju da hibridni algoritam ima dobru globalnu sposobnost pretraživanja, brzu konvergenciju, dobru kvalitetu rješenja i dobru performansu rezultata optimalizacije.Aiming at the problem of premature convergence of genetic algorithm and particle swarm algorithm, in order to let the two methods converge to the global optimal solution with the greatest probability and improve the efficiency of the algorithm, the paper will combine improved genetic algorithm with improved particle swarm optimization method to constitute mixed improved algorithm. Through multiple benchmark function used to test the performance of real hybrid genetic algorithm, the results show that hybrid algorithm has good global search ability, fast convergence, good quality of the solution, and good robust performance of its optimization results
Polyols Prepared from Ring-Opening Epoxidized Soybean Oil by a Castor Oil-Based Fatty Diol
Several biorenewable vegetable oil-based polyols with different molecular weights and various hydroxyl functionalities were successfully prepared by ring-opening epoxidized soybean oil with a castor oil-based fatty diol. It was found that several factors, including reaction time, reaction temperature, and molar ratios between epoxidized soybean oil and castor oil diol, affect structures and rheology behaviors of the final polyols. Proton NMR, FT-IR, GPC, and rheometry results revealed that the hydroxyl functionalities, molecular weight, and viscosity of the polyols could be tailored by controlling the above-mentioned factors. Besides, the role of solvents in the epoxy ring-opening process was investigated as well
A case crossover study on the impact of heat waves on non-accidental deaths in Jinan, China
Background: Heat waves can not only cause direct death from heat stroke but also lead to excess deaths due to other illnesses. Identifying contributing factors of population vulnerability to heat waves is particularly crucial because heat waves will affect the most disadvantaged populations aggravating health disparities. There has been little evidence on the risk of deaths from heat waves and associated contributing factors to the population vulnerability in Jinan. Purpose: To assess the impact of heat waves on non-accidental deaths and identify individual vulnerability factors to heat wave-related deaths in Jinan, China
Sunspot shearing and sudden retraction motion associated with the 2013 August 17 M3.3 Flare
In this Letter, we give a detailed analysis to the M3.3 class flare that
occurred on August 17, 2013 (SOL2013-08-17T18:16). It presents a clear picture
of mutual magnetic interaction initially from the photosphere to the corona via
the abrupt rapid shearing motion of a small sunspot before the flare, and then
suddenly from the corona back to the photosphere via the sudden retraction
motion of the same sunspot during the flare impulsive phase. About 10 hours
before the flare, a small sunspot in the active region NOAA 11818 started to
move northeast along a magnetic polarity inversion line (PIL), creating a
shearing motion that changed the quasi-static state of the active region. A
filament right above the PIL was activated following the movement of the
sunspot and then got partially erupted. The eruption eventually led to the M3.3
flare. The sunspot was then suddenly pulled back to the opposite direction upon
the flare onset. During the backward motion, the Lorentz force underwent a
simultaneous impulsive change both in magnitude and direction. Its directional
change is found to be conformable with the retraction motion. The observation
provides direct evidence for the role of the shearing motion of the sunspot in
powering and triggering the flare. It especially confirms that the abrupt
motion of a sunspot during a solar flare is the result of a back reaction
caused by the reconfiguration of the coronal magnetic field
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