226 research outputs found
Development of a Novel Green Surfactant - Low Salinity Nanofluid for Enhanced Oil Recovery Application
Natural surfactants have been considered part of the EOR processes, given their non-toxic and environment-friendly nature. In this project, two novel natural surfactants have been extracted. Furthermore, the physical-chemical properties of novel saponins, foamability and foam stability, interfacial tension (IFT), and wettability between saponins and low salinity water (LSW) and nanoparticles have been investigated. On the other hand, the interactions of the particles (mechanisms) between saponins, salt, nanoparticles, crude oil, and formation rocks have been examined
Generalized transfer matrix theory on electronic transport through graphene waveguide
In the effective mass approximation, electronic property in graphene can be
characterized by the relativistic Dirac equation. Within such a continuum model
we investigate the electronic transport through graphene waveguides formed by
connecting multiple segments of armchair-edged graphene nanoribbons of
different widths. By using appropriate wavefunction connection conditions at
the junction interfaces, we generalize the conventional transfer matrix
approach to formulate the linear conductance of the graphene waveguide in terms
of the structure parameters and the incident electron energy. In comparison
with the tight-binding calculation, we find that the generalized transfer
matrix method works well in calculating the conductance spectrum of a graphene
waveguide even with a complicated structure and relatively large size. The
calculated conductance spectrum indicates that the graphene waveguide exhibits
a well-defined insulating band around the Dirac point, even though all the
constituent ribbon segments are gapless. We attribute the occurrence of the
insulating band to the antiresonance effect which is intimately associated with
the edge states localized at the shoulder regions of the junctions.
Furthermore, such an insulating band can be sensitively shifted by a gate
voltage, which suggests a device application of the graphene waveguide as an
electric nanoswitch.Comment: 11 pages, 5 figure
Benchmarking the Physical-world Adversarial Robustness of Vehicle Detection
Adversarial attacks in the physical world can harm the robustness of
detection models. Evaluating the robustness of detection models in the physical
world can be challenging due to the time-consuming and labor-intensive nature
of many experiments. Thus, virtual simulation experiments can provide a
solution to this challenge. However, there is no unified detection benchmark
based on virtual simulation environment. To address this challenge, we proposed
an instant-level data generation pipeline based on the CARLA simulator. Using
this pipeline, we generated the DCI dataset and conducted extensive experiments
on three detection models and three physical adversarial attacks. The dataset
covers 7 continuous and 1 discrete scenes, with over 40 angles, 20 distances,
and 20,000 positions. The results indicate that Yolo v6 had strongest
resistance, with only a 6.59% average AP drop, and ASA was the most effective
attack algorithm with a 14.51% average AP reduction, twice that of other
algorithms. Static scenes had higher recognition AP, and results under
different weather conditions were similar. Adversarial attack algorithm
improvement may be approaching its 'limitation'.Comment: CVPR 2023 worksho
Temporal and spatial change of habitat quality and its driving forces: The case of Tacheng region, China
Habitat quality assessment is an important basis for ecological restoration practice. Taking the Tacheng region as an example, the InVEST model was used to evaluate the habitat quality of the Tacheng region in five periods from 2000 to 2020, and analyze the reasons for its changes, to provide theoretical guidance for ecological restoration practice in arid areas. The conclusions were that from 2000 to 2020, the habitat quality in the Tacheng region improved slightly, and the value of the habitat index in the Tacheng region was the highest in 2010, which was 0.577, and then decreased slightly. The habitat quality in the Tacheng region was significantly influenced by land use type conversion and precipitation. The change in land use type directly affected the change in habitat quality. The study region is located in an arid area; the forest land and grassland native to the region have more vegetation communities and genera of species and can be self-sustaining and resilient to disturbance, having high scores for habitat quality. The species of arable land is a monoculture; it cannot be self-sustaining and resilient to disturbance, and though it has high vegetation cover, the value of habitat quality is lower than that of forestland and grassland. The vegetation of unused land is rare, and the ecosystem of unused land is sensitive and vulnerable; the habitat quality scores are very low. The conversion of forest land, grassland, arable land, and unused land would directly affect the value of habitat quality, and conversion was the main factor affecting the change in habitat quality. In addition, precipitation was also an important factor affecting the change in habitat quality in the Tacheng region, which affected the biomass of natural vegetation and then affected the habitat quality. The results provided the temporal and spatial change of habitat quality and its driving forces in the Tacheng region, which helps determine appropriate measures and sites in ecological restoration projects
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