We study complex Chern–Simons theory on a Seifert manifold
M
3
by embedding it into string theory. We show that complex Chern–Simons theory on
M
3
is equivalent to a topologically twisted ...supersymmetric theory and its partition function can be naturally regularized by turning on a mass parameter. We find that the dimensional reduction of this theory to 2d gives the low energy dynamics of vortices in four-dimensional gauge theory, the fact apparently overlooked in the vortex literature. We also generalize the relations between (1) the Verlinde algebra, (2) quantum cohomology of the Grassmannian, (3) Chern–Simons theory on
Σ
×
S
1
and (4) index of a spin
c
Dirac operator on the moduli space of flat connections to a new set of relations between (1) the “equivariant Verlinde algebra” for a complex group, (2) the equivariant quantum K-theory of the vortex moduli space, (3) complex Chern–Simons theory on
Σ
×
S
1
and (4) the equivariant index of a spin
c
Dirac operator on the moduli space of Higgs bundles.
A
bstract
We study reductions of 6d theories on a
d
-dimensional manifold
M
d
, focusing on the interplay between symmetries, anomalies, and dynamics of the resulting (6
−
d
)-dimensional theory
T
M
...d
. We refine and generalize the notion of “polarization” to
polarization on M
d
, which serves to fix the spectrum of local and extended operators in
T
M
d
. Another important feature of theories
T
M
d
is that they often possess higher-group symmetries, such as 2-group and 3-group symmetries. We study the origin of such symmetries as well as physical implications including symmetry breaking and symmetry enhancement in the renormalization group flow. To better probe the IR physics, we also investigate the ’t Hooft anomaly of 5d Chern-Simons matter theories. The present paper focuses on developing the general framework as well as the special case of
d
= 0 and 1, while an upcoming paper will discuss the case of
d
= 2, 3 and 4.
Small-size (<5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions. However, ...arguments about the nature of the gold active site have continued for two decades, due to the lack of comparable catalyst systems with specific gold species, as well as the scarcity of direct experimental evidence for the reaction mechanism under realistic working conditions. Here we report the determination of the contribution of single atoms, clusters and particles to the oxidation of carbon monoxide at room temperature, by the aid of in situ X-ray absorption fine structure analysis and in situ diffuse reflectance infrared Fourier transform spectroscopy. We find that the metallic gold component in clusters or particles plays a much more critical role as the active site than the cationic single-atom gold species for the room-temperature carbon monoxide oxidation reaction.
A multifunctional three-dimensional lanthanide metal-organic framework has been rationally constructed. Highly selective sensing of benzaldehyde and Cu(2+) ions makes it a potential bifunctional ...sensor. Also, it could serve as a good candidate material for the removal of dyes from effluents based on the size exclusion.
•A data preprocessing approach named the dual decomposition strategy is developed.•A novel forecasting system is developed for electricity price forecasting.•The accuracy and stability of the ...forecasting system are improved simultaneously.•The applicability and effectiveness are verified in a real electricity market.
Electricity price forecasting plays a crucial role in balancing electricity generation and consumption, which is of great political and economic significance for all of society but is still a challenging task. However, in previous studies, most researchers have focused on improving either forecasting accuracy or stability while ignoring the significance of performing these tasks simultaneously. More importantly, few researchers have deeply studied the data preprocessing strategy, only focusing on the application of individual decomposition approaches. Therefore, a novel hybrid forecasting system based on a dual decomposition strategy and multi-objective optimization is developed for electricity price forecasting that includes four modules: a data preprocessing module, optimization module, forecasting module and evaluation module. In this system, an effective multi-objective optimization algorithm is employed to guarantee simultaneous improvements in accuracy and stability. In addition, an improved data preprocessing approach named the dual decomposition strategy is developed, which successfully overcomes the potential drawback of the individual decomposition approach and further improves the effectiveness of the developed forecasting system. Moreover, the evaluation module is incorporated to verify the superiority of the developed forecasting system. Case studies utilizing half-hourly electricity price data collected from New South Wales, Australia are employed as examples. The results prove the superiority of the multi-objective optimization algorithm and the developed dual decomposition strategy and reveal that the developed forecasting system outperforms all of the considered comparison models, which shows its better ability to forecast future electricity prices with better accuracy and stability.
Copper-ceria is one of the very active catalysts for the preferential oxidation of carbon monoxide (CO-PROX) reaction, which is also a typical system in which the complexity of copper chemistry is ...clearly exhibited. In the present manuscript, copper–ceria catalysts with different Cu contents up to 20 wt % supported on CeO2 nanorods were synthesized by a deposition–precipitation (DP) method. The as-prepared samples were characterized by various structural and textural detections including X-ray diffraction (XRD), Vis-Raman, transmission electron microscopy (TEM), ex situ/in situ X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H2-TPR). It has been confirmed that the highly dispersed copper oxide (CuO x ) clusters, as well as the strong interaction of Cu-O x -Ce structure, were the main copper species deposited onto the ceria surface. No separated copper phase was detected for both preoxidized and prereduced samples with the Cu contents up to 10 wt %. The fresh copper–ceria catalysts were pretreated in either O2- or H2-atmosphere and then tested for the CO-PROX reaction at a space velocity (SV) of 60 000 mL·h–1·gcat –1. The prereduced 5 and 10 wt % Cu samples exhibited excellent catalytic performance with high CO conversions (>50%, up to 100%) and O2 selectivities (>60%, up to 100%) within a wide temperature window of 80–140 °C. The in situ XAFS technique was carried out to monitor the structural evolution on the copper–ceria catalysts during the PROX experiments. The X-ray absorption near edge spectra (XANES) profiles, by the aid of linear combination analysis, identified the oxidized Cu(II) were the dominant copper species in both O2- and H2-pretreated samples after CO-PROX at 80 °C. Furthermore, the extended X-ray absorption fine structure (EXAFS) fitting results, together with the corresponding H2-TPR data distinctly determined that the highly dispersed CuO x (x = 0.2−0.5) cluster, other than the Cu–O x –Ce (x = 0.7−3.2) structure, were the crucial active species for the studied CO-PROX reaction.
A
bstract
We use Coulomb branch indices of Argyres-Douglas theories on
S
1
×
L
(
k,
1) to quantize moduli spaces
ℳ
H
of wild/irregular Hitchin systems. In particular, we obtain formulae for the “wild ...Hitchin characters” — the graded dimensions of the Hilbert spaces from quantization — for four infinite families of
ℳ
H
, giving access to many interesting geometric and topological data of these moduli spaces. We observe that the wild Hitchin characters can always be written as a sum over fixed points in
ℳ
H
under the U(1) Hitchin action, and a limit of them can be identified with matrix elements of the modular transform
ST
k
S
in certain two-dimensional chiral algebras. Although naturally fitting into the geometric Langlands program, the appearance of chiral algebras, which was known previously to be associated with Schur operators but not Coulomb branch operators, is somewhat surprising.
Electrical power system (EPS) forecasting plays a significant role in economic and social development but it remains an extremely challenging task. Because of its significance, relevant studies on ...EPS are especially needed. More specifically, only a few of the previous studies in this area conducted in-depth investigations of the entire EPS forecasting and merely focused on modeling individual signals centered on wind speed or electrical load. Moreover, most of these past studies concentrated on accuracy improvements and usually ignore the significance of forecasting stability. Therefore, to simultaneously achieve high accuracy and dependable stability, a hybrid forecasting framework based on the multi-objective dragonfly algorithm (MODA) was successfully developed in this study. The framework consists of four modules—data preprocessing, optimization, forecasting, and evaluation modules. In this framework, MODA is employed to optimize the Elman neural network (ENN) model as a part of the optimization module to overcome the drawbacks of single-objective optimization algorithms. In addition, data preprocessing and evaluation modules are incorporated to improve forecasting performance and conduct a comprehensive evaluation for this framework, respectively. Empirical results reveal that the developed forecasting framework can be an effective tool for the planning and management of power grids.
•A novel forecasting framework is developed for electrical power system.•Propose a modified Elman neural network based on multi-objective optimization.•The accuracy and stability of developed framework are improved simultaneously.•The results are validated well in a whole electrical power system.
Copper–ceria as one of the very active catalysts for oxidation reactions has been widely investigated in heterogeneous catalysis. In this work, copper oxide (1 wt % Cu loading) deposited on both ...ceria nanospheres with a {111}/{100}-terminated surface (1CuCe-NS) and with nanorod exposed {110}/{100} faces (1CuCe-NR) have been prepared for the investigation of crystal plane effects on CO oxidation. Various structural characterizations, especially including aberration-corrected scanning transmission electron microscopy (Cs-STEM), X-ray absorption fine structure (XAFS) technique, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), were used to precisely determine the structure and status of the catalysts. It is found that the copper oxides were formed as subnanometer clusters and were uniformly dispersed on the surface of the ceria support. The results from XAFS combined with the temperature-programmed reduction technique (H2-TPR) reveal that more reducible CuO x clusters with only Cu–O coordination structure exclusively dominated in the surface of 1CuCe-NS, while the Cu species in 1CuCe-NR existed in both CuO x clusters and strongly interacting Cu-O x -Ce. In situ DRIFTS results demonstrate that the CeO2-{110} face induced a strongly bound Cu-O x -Ce structure in 1CuCe-NR which was adverse to the formation of reduced Cu(I) active sites, resulting in low reactivity in CO oxidation (r CO = 1.8 × 10–6 molCO gcat –1 s–1 at 118 °C); in contrast, CuO x clusters on the CeO2-{111} face were easily reduced to Cu(I) species when they were subjected to interaction with CO, which greatly enhanced the catalytic reactivity (r CO = 5.7 × 10–6 molCO gcat –1 s–1 at 104 °C). Thus, for copper–ceria catalyst, in comparison with the well-known reactive {110}CeO2 plane, {111}CeO2, the most inert plane, exhibits great superiority to induce more catalytically active sites of CuO x clusters. The difference in strength of the interaction between copper oxides and different exposed faces of ceria is intrinsically relevant to the different redox and catalytic properties.
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