69 research outputs found
Solar cycle variation of real CME latitudes
With the assumption of radial motion and uniform longitudinal distribution of
coronal mass ejections (CMEs), we propose a method to eliminate projection
effects from the apparent observed CME latitude distribution. This method has
been applied to SOHO LASCO data from 1996 January to 2006 December. As a
result, we find that the real CME latitude distribution had the following
characteristics: (1) High-latitude CMEs ( where is
the latitude) constituted 3% of all CMEs and mainly occurred during the time
when the polar magnetic fields reversed sign. The latitudinal drift of the
high-latitude CMEs was correlated with that of the heliospheric current sheet.
(2) 4% of all CMEs occurred in the range .
These mid-latitude CMEs occurred primarily in 2000, near the middle of 2002 and
in 2005, respectively, forming a prominent three-peak structure; (3) The
highest occurrence probability of low-latitude () CMEs was
at the minimum and during the declining phase of the solar cycle. However, the
highest occurrence rate of low-latitude CMEs was at the maximum and during the
declining phase of the solar cycle. The latitudinal evolution of low-latitude
CMEs did not follow the Sp\"{o}rer sunspot law, which suggests that many CMEs
originated outside of active regions.Comment: 4 pages, 4 figures, accepted by ApJ Lette
A multicomponent assembly approach for the design of deep desulfurization heterogeneous catalysts
Deep desulfurization is a challenging task and global efforts are focused on the development of new approaches for the reduction of sulfur-containing compounds in fuel oils. In this work, we have proposed a new design strategy for the development of deep desulfurization heterogeneous catalysts. Based on the adopted design strategy, a novel composite material of polyoxometalate (POM)-based ionic liquid-grafted layered double hydroxides (LDHs) was synthesized by an exfoliation/grafting/assembly process. The structural properties of the as-prepared catalyst were characterized using FT-IR, XRD, TG, NMR, XPS, BET, SEM and HRTEM. The heterogeneous catalyst exhibited high activity in deep desulfurization of DBT (dibenzothiophene), 4,6-DMDBT (4,6-dimethyldibenzothiophene) and BT (benzothiophene) at 70 °C in 25, 30 and 40 minutes, respectively. The catalyst can be easily recovered and reused at least ten times without obvious decrease of its catalytic activity. Such excellent sulfur removal ability as well as the cost efficiency of the novel heterogeneous catalyst can be attributed to the rational design, where the spatial proximity of the substrate and the active sites, the immobilization of ionic liquid onto the LDHs via covalent bonding and the recyclability of the catalyst are carefully considered
Spin Space Groups: Full Classification and Applications
In this work, we exhaust all the spin-space symmetries, which fully
characterize collinear, non-collinear, commensurate, and incommensurate spiral
magnetism, and investigate enriched features of electronic bands that respect
these symmetries. We achieve this by systematically classifying the so-called
spin space groups (SSGs) - joint symmetry groups of spatial and spin operations
that leave the magnetic structure unchanged. Generally speaking, they are
accurate (approximate) symmetries in systems where spin-orbit coupling (SOC) is
negligible (finite but weaker than the interested energy scale); but we also
show that specific SSGs could remain valid even in the presence of a strong
SOC. By representing the SSGs as O() representations, we - for the first
time - obtain the complete classifications of 1421, 9542, and 56512 distinct
SSGs for collinear (), coplanar (), and non-coplanar ()
magnetism, respectively. SSG not only fully characterizes the symmetry of spin
d.o.f., but also gives rise to exotic electronic states, which, in general,
form projective representations of magnetic space groups (MSGs). Surprisingly,
electronic bands in SSGs exhibit features never seen in MSGs, such as
nonsymmorphic SSG Brillouin zone (BZ), where SSG operations behave as glide or
screw when act on momentum and unconventional spin-momentum locking, which is
completely determined by SSG, independent of Hamiltonian details. To apply our
theory, we identify the SSG for each of the 1604 published magnetic structures
in the MAGNDATA database on the Bilbao Crystallographic Server. Material
examples exhibiting aforementioned novel features are discussed with emphasis.
We also investigate new types of SSG-protected topological electronic states
that are unprecedented in MSGs
Complexity analysis of weakly noisy quantum states via quantum machine learning
Quantum computers capable of fault-tolerant operation are expected to provide
provable advantages over classical computational models. However, the question
of whether quantum advantages exist in the noisy intermediate-scale quantum era
remains a fundamental and challenging problem. The root of this challenge lies
in the difficulty of exploring and quantifying the power of noisy quantum
states. In this work, we focus on the complexity of weakly noisy states, which
we define as the size of the shortest quantum circuit required to prepare the
noisy state. To analyze the complexity, we propose a quantum machine learning
(QML) algorithm that exploits the intrinsic-connection property of structured
quantum neural networks. The proposed QML algorithm enables efficiently
predicting the complexity of weakly noisy states from measurement results,
representing a paradigm shift in our ability to characterize the power of noisy
quantum computation
Trainability Analysis of Quantum Optimization Algorithms from a Bayesian Lens
The Quantum Approximate Optimization Algorithm (QAOA) is an extensively
studied variational quantum algorithm utilized for solving optimization
problems on near-term quantum devices. A significant focus is placed on
determining the effectiveness of training the -qubit QAOA circuit, i.e.,
whether the optimization error can converge to a constant level as the number
of optimization iterations scales polynomially with the number of qubits. In
realistic scenarios, the landscape of the corresponding QAOA objective function
is generally non-convex and contains numerous local optima. In this work,
motivated by the favorable performance of Bayesian optimization in handling
non-convex functions, we theoretically investigate the trainability of the QAOA
circuit through the lens of the Bayesian approach. This lens considers the
corresponding QAOA objective function as a sample drawn from a specific
Gaussian process. Specifically, we focus on two scenarios: the noiseless QAOA
circuit and the noisy QAOA circuit subjected to local Pauli channels. Our first
result demonstrates that the noiseless QAOA circuit with a depth of
can be trained efficiently,
based on the widely accepted assumption that either the left or right slice of
each block in the circuit forms a local 1-design. Furthermore, we show that if
each quantum gate is affected by a -strength local Pauli channel with the
noise strength range of to 0.1, the noisy QAOA circuit with
a depth of can also be trained
efficiently. Our results offer valuable insights into the theoretical
performance of quantum optimization algorithms in the noisy intermediate-scale
quantum era
An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography : Implications for aerosol pH estimate
Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl-, SO2-4, NO-3, NHC4 and KC. However, F-, Mg2C and Ca2C were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO2-4, NO-3 and NHC4 generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl-from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl-, SO2-4, NO-3, NHC4 and KC across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl-, SO2-4, NO-3, NHC4 and KC decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE/CE) and ion balance (anions-cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent
Tratamiento interdisciplinario del espacio literario en la serie de novelas Manolito Gafotas
Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Filosofía y Letras, Departamento de Filología Española. Fecha de lectura: 16-12-2021Esta tesis tiene embargado el acceso al texto completo hasta el 16-06-2023Haciendo uso de una voz infantil y de una ubicación geográfica precisa, la serie
de novelas Manolito Gafotas ofrece un collage literario, geográfico y emocional de
Madrid y del barrio de Carabanchel Alto a finales de siglo XX, proponiendo una lectura
de la identidad geográfica, social y cultural de sus espacios urbanos. La presente tesis
doctoral presenta un acercamiento multidisciplinar a la serie de novelas Manolito
Gafotas mediante un énfasis teórico en el punto de vista de la geografía humanística,
para poner de relieve el efecto multidimensional de sus espacios. A lo largo la tesis se
lleva a cabo una lectura sociológica, fenomenológica, filosófica y literaria sobre los
espacios en la serie de novelas juveniles en cuestió
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