arXiv subjects

Yuyun Yang

Publications and source records attributed to Yuyun Yang.

3 recordsLinked to original sources

arXiv2021

Short-Term Electricity Price Forecasting based on Graph Convolution Network and Attention Mechanism

In electricity markets, locational marginal price (LMP) forecasting is particularly important for market participants in making reasonable bidding strategies, managing potential trading risks, and supporting efficient system planning and operation. Unlike existing methods that only consider LMPs' temporal features, this paper tailors a spectral graph convolutional network (GCN) to greatly improve the accuracy of short-term LMP forecasting. A three-branch network structure is then designed to match the structure of LMPs' compositions. Such kind of network can extract the spatial-temporal features of LMPs, and provide fast and high-quality predictions for all nodes simultaneously. The attention mechanism is also implemented to assign varying importance weights between different nodes and time slots. Case studies based on the IEEE-118 test system and real-world data from the PJM validate that the proposed model outperforms existing forecasting models in accuracy, and maintains a robust performance by avoiding extreme errors.

cs.LG↗

arXiv2020

Fault Valving and Pore Pressure Evolution in Simulations of Earthquake Sequences and Aseismic Slip

Fault-zone fluids control effective normal stress and fault strength. While most earthquake models assume a fixed pore fluid pressure distribution, geologists have documented fault valving behavior, that is, cyclic changes in pressure and unsteady fluid migration along faults. Here we quantify fault valving through 2-D antiplane shear simulations of earthquake sequences on a strike-slip fault with rate-and-state friction, upward Darcy flow along a permeable fault zone, and permeability evolution. Fluid overpressure develops during the interseismic period, when healing/sealing reduces fault permeability, and is released after earthquakes enhance permeability. Coupling between fluid flow, permeability and pressure evolution, and slip produces fluid-driven aseismic slip near the base of the seismogenic zone and earthquake swarms within the seismogenic zone, as ascending fluids pressurize and weaken the fault. This model might help explain observations of late interseismic fault unlocking, slow slip and creep transients, swarm seismicity, and rapid pressure/stress transmission in induced seismicity sequences.

physics.geo-ph↗

arXiv2020

Noble metal free photocatalytic H$_2$ generation on black TiO$_2$: On the influence of crystal facets vs. crystal damage

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation (HPH) and hydrogen ion-implantation. We find that on the natural, intact low index planes photocatalytic H$_2$ evolution (in absence of noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching, miscut in the wafer or by implantation damage. X-ray reflectivity (XRR), Raman, and optical reflection measurements show that plain hydrogenation leads to a ~ 1 nm thick black titania surface layer without activity, while a colorless, density modified and ~ 7 nm thick layer with broken crystal symmetry is present in the ion implanted surface. These results demonstrate that i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation, and ii) activation does not necessarily coincide with the presence of black color.

physics.app-ph↗