2,108 research outputs found
Quantitative Concentrations of Sodium and Potassium Released from Brown Coal and Pine Wood in a Laminar Premixed Flame Using Libs
A quantitative point measurement of total sodium and potassium released during combustion of Australian Loy Yang brown coal particles (23 ± 3 mg) and pine wood pellets (63 ± 3 mg) has been performed using laser-induced breakdown spectroscopy (LIBS) in a laminar premixed methane flame at the equivalence ratio (Φ) of 1.287. Calibration was performed using droplets of sodium sulfite (Na2SO3) and potassium sulphate (K2SO4) entrained into the flame. A correction to the calibration curve was applied to compensate for the significant absorption effect caused by atomic alkalis in outer seeded flame, which significantly improved the calibration reliability especially at high concentrations. Hence quantitative release of sodium and potassium during the three phases of combustion, namely devolatilization, char and ash cooking, were obtained. The concentration of total sodium in the plume released from combustion of pine wood pellets during the devolatilization reached up to 15 ppm indicating significant sodium was released in various forms. The strongest concentrations of total sodium and potassium released during char phase of both coal and wood reaching up to 21.3 and 2.4 ppm, 15.5 and 26.3 ppm, respectively. Limit of Detection (LOD) of sodium and potassium with LIBS in the present setup were estimated to be 0.029 and 0.072 ppm, respectively.Li-Jen Hsu, Zeyad Alwahabi, Graham Nathan, Peter Ashman, Keith Kinghttp://www.chemeca2010.com/abstract/226.as
Learning Shape Priors for Single-View 3D Completion and Reconstruction
The problem of single-view 3D shape completion or reconstruction is
challenging, because among the many possible shapes that explain an
observation, most are implausible and do not correspond to natural objects.
Recent research in the field has tackled this problem by exploiting the
expressiveness of deep convolutional networks. In fact, there is another level
of ambiguity that is often overlooked: among plausible shapes, there are still
multiple shapes that fit the 2D image equally well; i.e., the ground truth
shape is non-deterministic given a single-view input. Existing fully supervised
approaches fail to address this issue, and often produce blurry mean shapes
with smooth surfaces but no fine details.
In this paper, we propose ShapeHD, pushing the limit of single-view shape
completion and reconstruction by integrating deep generative models with
adversarially learned shape priors. The learned priors serve as a regularizer,
penalizing the model only if its output is unrealistic, not if it deviates from
the ground truth. Our design thus overcomes both levels of ambiguity
aforementioned. Experiments demonstrate that ShapeHD outperforms state of the
art by a large margin in both shape completion and shape reconstruction on
multiple real datasets.Comment: ECCV 2018. The first two authors contributed equally to this work.
Project page: http://shapehd.csail.mit.edu
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Surface/Interface Carrier-Transport Modulation for Constructing Photon-Alternative Ultraviolet Detectors Based on Self-Bending-Assembled ZnO Nanowires.
Surface/interface charge-carrier generation, diffusion, and recombination/transport modulation are especially important in the construction of photodetectors with high efficiency in the field of nanoscience. In the paper, a kind of ultraviolet (UV) detector is designed based on ZnO nanostructures considering photon-trapping, surface plasmonic resonance (SPR), piezophototronic effects, interface carrier-trapping/transport control, and collection. Through carefully optimized surface/interface carrier-transport modulation, a designed device with detectivity as high as 1.69 × 1016/1.71 × 1016 cm·Hz1/2/W irradiating with 380 nm photons under ultralow bias of 0.2 V is realized by alternating nanoparticle/nanowire active layers, respectively, and the designed UV photodetectors show fast and slow recovery processes of 0.27 and 4.52 ms, respectively, which well-satisfy practical needs. Further, it is observed that UV photodetection could be performed within an alternative response by varying correlated key parameters, through efficient surface/interface carrier-transport modulation, spectrally resolved photoresponse of the detector revealing controlled detection in the UV region based on the ZnO nanomaterial, photodetection allowed or limited by varying the active layers, irradiation distance from one of the electrodes, standing states, or electric field. The detailed carrier generation, diffusion, and recombination/transport processes are well illustrated to explain charge-carrier dynamics contributing to the photoresponse behavior
TimelineQA: A Benchmark for Question Answering over Timelines
Lifelogs are descriptions of experiences that a person had during their life.
Lifelogs are created by fusing data from the multitude of digital services,
such as online photos, maps, shopping and content streaming services. Question
answering over lifelogs can offer personal assistants a critical resource when
they try to provide advice in context. However, obtaining answers to questions
over lifelogs is beyond the current state of the art of question answering
techniques for a variety of reasons, the most pronounced of which is that
lifelogs combine free text with some degree of structure such as temporal and
geographical information.
We create and publicly release TimelineQA1, a benchmark for accelerating
progress on querying lifelogs. TimelineQA generates lifelogs of imaginary
people. The episodes in the lifelog range from major life episodes such as high
school graduation to those that occur on a daily basis such as going for a run.
We describe a set of experiments on TimelineQA with several state-of-the-art QA
models. Our experiments reveal that for atomic queries, an extractive QA system
significantly out-performs a state-of-the-art retrieval-augmented QA system.
For multi-hop queries involving aggregates, we show that the best result is
obtained with a state-of-the-art table QA technique, assuming the ground truth
set of episodes for deriving the answer is available
Dye-Assisted Transformation of Cu2O Nanocrystal to Amorphous CuxO Nano Flake for Enhanced Photocatalytic Performance
Amorphous CuxO nano flakes with a thickness of 10 to 50 nm were synthesized through the dye-assisted transformation of rhombic dodecahedral Cu2O nanocrystals using facile solution process. The morphology evolution observed by electron microscopy is highly dependent on the reaction between the surface and the dye. The crystal grain shrinks during the process until the formation of a purely amorphous nano flake. The amorphous CuxO nano flake consists of a combination of Cu(I) and Cu(II) with a ratio close to 1:1. It shows enhanced photocatalytic reactivity towards the degradation of methyl orange as compared to rhombic dodecahedral Cu2O nanocrystals with all active (110):Cu facets. The chemical composition and architecture remain the same after repeating degradation tests. The high surface-to-volume ratio contributes to its superior photocatalytic performance while its low surface energy, confirmed by density functional theory simulations, explains its improved stability. The nano flakes also shows the ability to degrade nitrobenzene effectively, thus demonstrating great promise as a highly stable and active photocatalyst for environmental applications.This work was funded by the Engineering and Physical Sciences Research Council under Project EP/M013650/1
Deep-Learning-based Fast and Accurate 3D CT Deformable Image Registration in Lung Cancer
Purpose: In some proton therapy facilities, patient alignment relies on two
2D orthogonal kV images, taken at fixed, oblique angles, as no 3D on-the-bed
imaging is available. The visibility of the tumor in kV images is limited since
the patient's 3D anatomy is projected onto a 2D plane, especially when the
tumor is behind high-density structures such as bones. This can lead to large
patient setup errors. A solution is to reconstruct the 3D CT image from the kV
images obtained at the treatment isocenter in the treatment position.
Methods: An asymmetric autoencoder-like network built with vision-transformer
blocks was developed. The data was collected from 1 head and neck patient: 2
orthogonal kV images (1024x1024 voxels), 1 3D CT with padding (512x512x512)
acquired from the in-room CT-on-rails before kVs were taken and 2
digitally-reconstructed-radiograph (DRR) images (512x512) based on the CT. We
resampled kV images every 8 voxels and DRR and CT every 4 voxels, thus formed a
dataset consisting of 262,144 samples, in which the images have a dimension of
128 for each direction. In training, both kV and DRR images were utilized, and
the encoder was encouraged to learn the jointed feature map from both kV and
DRR images. In testing, only independent kV images were used. The full-size
synthetic CT (sCT) was achieved by concatenating the sCTs generated by the
model according to their spatial information. The image quality of the
synthetic CT (sCT) was evaluated using mean absolute error (MAE) and
per-voxel-absolute-CT-number-difference volume histogram (CDVH).
Results: The model achieved a speed of 2.1s and a MAE of <40HU. The CDVH
showed that <5% of the voxels had a per-voxel-absolute-CT-number-difference
larger than 185 HU.
Conclusion: A patient-specific vision-transformer-based network was developed
and shown to be accurate and efficient to reconstruct 3D CT images from kV
images.Comment: 9 figure
Effects of anisotropic interactions on the structure of animal groups
This paper proposes an agent-based model which reproduces different
structures of animal groups. The shape and structure of the group is the effect
of simple interaction rules among individuals: each animal deploys itself
depending on the position of a limited number of close group mates. The
proposed model is shown to produce clustered formations, as well as lines and
V-like formations. The key factors which trigger the onset of different
patterns are argued to be the relative strength of attraction and repulsion
forces and, most important, the anisotropy in their application.Comment: 22 pages, 9 figures. Submitted. v1-v4: revised presentation; extended
simulations; included technical results. v5: added a few clarification
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