140 research outputs found
Topology design of an offshore wind farm with multiple types of wind turbines in a circular layout
The advances in the manufacturing industry make it possible to install wind turbines (WTs) with large capacities in offshore wind farms (OWFs) in deep water areas far away from the coast where there are the best wind resources. This paper proposes a novel method for OWF optimal planning in deep water areas with a circular boundary. A three-dimensional model of the planning area’s seabed is established in a cylindrical coordinate. Two kinds of WTs with capacities of 4 and 8 MW respectively are supposed to be mixed-installed in that area. Baseline cases are analyzed and compared to verify the superiority of a circular layout pattern and the necessity of a non-uniform installation. Based on the establishment of the optimization model and a realistic wind condition, a novel heuristic algorithm, i.e., the whale optimization algorithm (WOA), is applied to solve the problem to obtain the type selection and coordinates of WTs simultaneously. Finally, the feasibility and advantages of the proposed scheme are identified and discussed according to the simulation results
Free Ferrous Ions Sustain Activity of Mammalian Stearoyl-CoA Desaturase-1
Mammalian stearoyl-CoA desaturase-1 (SCD1) introduces a double-bond to a saturated long-chain fatty acid in a reaction catalyzed by a diiron center. The diiron center is well-coordinated by conserved histidine residues and is thought to remain with the enzyme. However, we find here that SCD1 progressively loses its activity during catalysis and becomes fully inactive after about nine turnovers. Further studies show that the inactivation of SCD1 is due to the loss of an iron (Fe) ion in the diiron center and that the addition of free ferrous ions (F
Role of Nanolaminated Crystal Structure on the Radiation Damage Tolerance of Ti 3
Nanolaminated Ti3SiC2, a representative MAX phase,
shows excellent tolerance to radiation damage. In this paper, first-principles
calculations were used to investigate the mechanism of intrinsic point defects
in order to explain this outstanding property. Formation energies of intrinsic point
defects are calculated and compared; and the results establish a low-energy disorder
mechanism in Ti3SiC2. In addition, the migration energy
barriers of Si vacancy, Si interstitial, and TiSi antisite yield very low values: 0.9, 0.6, and 0.3 eV, respectively.
The intercalation of Si atomic plane between Ti3C2 nanotwinning
structures dominates the formation and migration of intrinsic native point defects
in Ti3SiC2. The present study also highlights a novel method
to improve radiation damage tolerance by developing nanoscale-layered structure which
can serve as a sink or rapid recovery channel for point defects
Segment Anything in 3D with NeRFs
The Segment Anything Model (SAM) has demonstrated its effectiveness in
segmenting any object/part in various 2D images, yet its ability for 3D has not
been fully explored. The real world is composed of numerous 3D scenes and
objects. Due to the scarcity of accessible 3D data and high cost of its
acquisition and annotation, lifting SAM to 3D is a challenging but valuable
research avenue. With this in mind, we propose a novel framework to Segment
Anything in 3D, named SA3D. Given a neural radiance field (NeRF) model, SA3D
allows users to obtain the 3D segmentation result of any target object via only
one-shot manual prompting in a single rendered view. With input prompts, SAM
cuts out the target object from the according view. The obtained 2D
segmentation mask is projected onto 3D mask grids via density-guided inverse
rendering. 2D masks from other views are then rendered, which are mostly
uncompleted but used as cross-view self-prompts to be fed into SAM again.
Complete masks can be obtained and projected onto mask grids. This procedure is
executed via an iterative manner while accurate 3D masks can be finally
learned. SA3D can adapt to various radiance fields effectively without any
additional redesigning. The entire segmentation process can be completed in
approximately two minutes without any engineering optimization. Our experiments
demonstrate the effectiveness of SA3D in different scenes, highlighting the
potential of SAM in 3D scene perception. The project page is at
https://jumpat.github.io/SA3D/.Comment: Work in progress. Project page: https://jumpat.github.io/SA3D
Screening and simulation of offshore CO2-EOR and storage:A case study for the HZ21-1 oilfield in the Pearl River Mouth Basin, Northern South China Sea
CO2-enhanced oil recovery (CO2-EOR) and storage is currently the most effective and economic technology for reducing CO2 emissions from burning fossil fuels in large scale. This paper is the first effort of proposing a modelling assessment of CO2-EOR and storage in the HZ2-1 oilfield in the Pearl River Mouth Basin in northern South China Sea offshore Guangdong Province. We attempt to couple the multi-parameter dimensionless quick screening model and reservoir compositional simulation for optimization of site screen and injection simulation. Through the quick screening, the reservoirs are ranked by FOR dimensionless recovery R-D, and by CO2 storage in pore volume SCO2. Our results indicate that SCO2 is highly pressure dependent and not directly related to R-D. Of these reservoirs, CO2-EOR and storage potential of the M10 was estimated through a compositional simulation as a case study based on a 3D geological model. Nine scenarios of CO2 injection operations have been simulated for 20 years with different well patterns and injection pressures. The simulation results represent an obvious improvement in oil production by CO2 flooding over No - CO2 production. The best operation for M10 is miscible CO2 flooding, which led to the higher recovery factors of 52%(similar to)58% and CO 2 stored masses of 8.1 x 10(6 similar to)10.8 x 10(6)t The optimum operation for CO2 injection should be set well pattern in region of injector I1 and high injection pressure for miscible flooding. In a whole, the HZ21-1 field can be used as a candidate geological site for GDCCUS project. We are fully aware of the limitation in the primary modelling including reservoir and fluid properties and production history matching, and regard this study as a general and hypothetic proposal
Pattern recognition receptors in the development of nonalcoholic fatty liver disease and progression to hepatocellular carcinoma: An emerging therapeutic strategy
Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation and has become the leading chronic liver disease worldwide. NAFLD is viewed as the hepatic manifestation of metabolic syndrome, ranging from simple steatosis and nonalcoholic steatohepatitis (NASH) to advanced fibrosis, eventually leading to cirrhosis and hepatocellular carcinoma (HCC). The pathogenesis of NAFLD progression is still not clear. Pattern recognition receptor (PRR)-mediated innate immune responses play a critical role in the initiation of NAFLD and the progression of NAFLD-related HCC. Toll-like receptors (TLRs) and the cyclic GMP-AMP (cGAMP) synthase (cGAS) are the two major PRRs in hepatocytes and resident innate immune cells in the liver. Increasing evidence indicates that the overactivation of TLRs and the cGAS signaling pathways may contribute to the development of liver disorders, including NAFLD progression. However, induction of PRRs is critical for the release of type I interferons (IFN-I) and the maturation of dendritic cells (DCs), which prime systemic antitumor immunity in HCC therapy. In this review, we will summarize the emerging evidence regarding the molecular mechanisms of TLRs and cGAS in the development of NAFLD and HCC. The dysfunction of PRR-mediated innate immune response is a critical determinant of NAFLD pathology; targeting and selectively inhibiting TLRs and cGAS signaling provides therapeutic potential for treating NALF-associated diseases in humans
TiAVox: Time-aware Attenuation Voxels for Sparse-view 4D DSA Reconstruction
Four-dimensional Digital Subtraction Angiography (4D DSA) plays a critical
role in the diagnosis of many medical diseases, such as Arteriovenous
Malformations (AVM) and Arteriovenous Fistulas (AVF). Despite its significant
application value, the reconstruction of 4D DSA demands numerous views to
effectively model the intricate vessels and radiocontrast flow, thereby
implying a significant radiation dose. To address this high radiation issue, we
propose a Time-aware Attenuation Voxel (TiAVox) approach for sparse-view 4D DSA
reconstruction, which paves the way for high-quality 4D imaging. Additionally,
2D and 3D DSA imaging results can be generated from the reconstructed 4D DSA
images. TiAVox introduces 4D attenuation voxel grids, which reflect attenuation
properties from both spatial and temporal dimensions. It is optimized by
minimizing discrepancies between the rendered images and sparse 2D DSA images.
Without any neural network involved, TiAVox enjoys specific physical
interpretability. The parameters of each learnable voxel represent the
attenuation coefficients. We validated the TiAVox approach on both clinical and
simulated datasets, achieving a 31.23 Peak Signal-to-Noise Ratio (PSNR) for
novel view synthesis using only 30 views on the clinically sourced dataset,
whereas traditional Feldkamp-Davis-Kress methods required 133 views. Similarly,
with merely 10 views from the synthetic dataset, TiAVox yielded a PSNR of 34.32
for novel view synthesis and 41.40 for 3D reconstruction. We also executed
ablation studies to corroborate the essential components of TiAVox. The code
will be publically available.Comment: 10 pages, 8 figure
La torre de doña Urraca en Covarrubias (Burgos)
La torre de doña Urraca en Covarrubias (Burgos
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Unraveling the Orbital Physics in a Canonical Orbital System KCuF3
We explore the existence of the collective orbital excitations, orbitons, in the canonical orbital system KCuF3 using the Cu L3-edge resonant inelastic x-ray scattering. We show that the nondispersive high-energy peaks result from the Cu2+  dd orbital excitations. These high-energy modes display good agreement with the ab initio quantum chemistry calculation, indicating that the dd excitations are highly localized. At the same time, the low-energy excitations present clear dispersion. They match extremely well with the two-spinon continuum following the comparison with Müller ansatz calculations. The localized dd excitations and the observation of the strongly dispersive magnetic excitations suggest that the orbiton dispersion is below the resolution detection limit. Our results can reconcile with the strong local Jahn-Teller effect in KCuF3, which predominantly drives orbital ordering
Correlation driven near-flat band Stoner excitations in a Kagome magnet
Among condensed matter systems, Mott insulators exhibit diverse properties
that emerge from electronic correlations. In itinerant metals, correlations are
usually weak, but can also be enhanced via geometrical confinement of
electrons, that manifest as `flat' dispersionless electronic bands. In the fast
developing field of topological materials, which includes Dirac and Weyl
semimetals, flat bands are one of the important components that can result in
unusual magnetic and transport behaviour. To date, characterisation of flat
bands and their magnetism is scarce, hindering the design of novel materials.
Here, we investigate the ferromagnetic Kagom\'{e} semimetal CoSnS
using resonant inelastic X-ray scattering. Remarkably, nearly non-dispersive
Stoner spin excitation peaks are observed, sharply contrasting with the
featureless Stoner continuum expected in conventional ferromagnetic metals. Our
band structure and dynamic spin susceptibility calculations, and thermal
evolution of the excitations, confirm the nearly non-dispersive Stoner
excitations as unique signatures of correlations and spin-polarized electronic
flat bands in CoSnS. These observations serve as a cornerstone for
further exploration of band-induced symmetry-breaking orders in topological
materials.Comment: 15 pages, 4 figures, and Supplementary Informatio
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