2,081 research outputs found
Automatic Seismic Salt Interpretation with Deep Convolutional Neural Networks
One of the most crucial tasks in seismic reflection imaging is to identify
the salt bodies with high precision. Traditionally, this is accomplished by
visually picking the salt/sediment boundaries, which requires a great amount of
manual work and may introduce systematic bias. With recent progress of deep
learning algorithm and growing computational power, a great deal of efforts
have been made to replace human effort with machine power in salt body
interpretation. Currently, the method of Convolutional neural networks (CNN) is
revolutionizing the computer vision field and has been a hot topic in the image
analysis. In this paper, the benefits of CNN-based classification are
demonstrated by using a state-of-art network structure U-Net, along with the
residual learning framework ResNet, to delineate salt body with high precision.
Network adjustments, including the Exponential Linear Units (ELU) activation
function, the Lov\'{a}sz-Softmax loss function, and stratified -fold
cross-validation, have been deployed to further improve the prediction
accuracy. The preliminary result using SEG Advanced Modeling (SEAM) data shows
good agreement between the predicted salt body and manually interpreted salt
body, especially in areas with weak reflections. This indicates the great
potential of applying CNN for salt-related interpretations.Comment: 11 pages, 7 figure
The Acoustic Emission Technique Research on Dynamic Damage Characteristics of the Coal Rock
AbstractThe acoustic emission technique is used to research the deformation and the failure process, investigate the deformation and injury regularity, discuss the physical process of acoustic emission of the coal and gas outburst and reveal the evolution process and disaster mechanism of the coal rock dynamic disaster. In this paper, the relationship between the damage and the acoustic emission is researched to get the coal cock damage expression which is expressed by the acoustic emission cumulative value. Meanwhile, the quasi-static is used to analyze the evolution process of the coal rock's inner damage and describe the coal rock's single axis damage character. On the base of the coal rock unit damage model, the constitutive relationship of acoustic emission coal rock is studied, which is the theory analysis for the coal and gas outburst. It is very significant for the research of the coal and gas outburst mechanism and prediction
Standard metabolic rate predicts growth trajectory of juvenile Chinese crucian carp (Carassius auratus) under changing food availability
Phenotypic traits vary greatly within populations and can have a significant influence on aspects of performance. The present study aimed to investigate the effects of individual variation in standard metabolic rate (SMR) on growth rate and tolerance to food-deprivation in juvenile crucian carp (Carassius auratus) under varying levels of food availability. To address this issue, 19 high and 16 low SMR (individuals were randomly assigned to a satiation diet for 3 weeks, whereas another 20 high and 16 low SMR individuals were assigned to a restricted diet (approximately 50% of satiation) for the same period. Then, all fish were completely food-deprived for another 3 weeks. High SMR individuals showed a higher growth rate when fed to satiation, but this advantage of SMR did not exist in food-restricted fish. This result was related to improved feeding efficiency with decreased food intake in low SMR individuals, due to their low food processing capacity and maintenance costs. High SMR individuals experienced more mass loss during food-deprivation as compared to low SMR individuals. Our results here illustrate context-dependent costs and benefits of intraspecific variation in SMR whereby high SMR individuals show increased growth performance under high food availability but had a cost under stressful environments (i.e., food shortage)
The Development and Validation of an EFL Learner Attitude Scale for Phonetic Symbol Learning in A Chinese University Context
Research has established that learner attitude significantly impacts the outcomes of learning English as a foreign language (EFL). However, previous studies have rarely considered a validated attitude scale for English phonetic symbol learning (EPSL). This study aims to develop and validate a scale to measure students\u27 attitudes toward EPSL by integrating findings from learning attitude research in education and psychology. The results demonstrate that the attitude scale can predict attitudes towards EPSL in the context of a Chinese university and has good reliability and validity (KMO=0.892, α=0.749). Pedagogical suggestions are made to help students develop a more positive attitude toward EPSL
Theoretical Study on Rotational Bands and Shape Coexistence of {Tl} in the Particle Triaxial-Rotor Model
By taking the particle triaxial-rotor model with variable moment of inertia,
we investigate the energy spectra, the deformations and the single particle
configurations of the nuclei Tl systemically. The calculated
energy spectra agree with experimental data quite well. The obtained results
indicate that the aligned bands observed in Tl originate from
the , , proton
configuration coupled to a prolate deformed core, respectively. Whereas, the
negative parity bands built upon the isomeric states in
Tl are formed by a proton with the
configuration coupled to a core with triaxial oblate deformation, and the
positive parity band on the isomeric state in Tl is
generated by a proton with configuration coupled to a
triaxial oblate core.Comment: 16 pages, 5 figures. To appear in Physical Review
Multi-chromatic narrow-energy-spread electron bunches from laser wakefield acceleration with dual-color lasers
A method based on laser wakefield acceleration with controlled ionization
injection triggered by another frequency-tripled laser is proposed, which can
produce electron bunches with low energy spread. As two color pulses
co-propagate in the background plasma, the peak amplitude of the combined laser
field is modulated in time and space during the laser propagation due to the
plasma dispersion. Ionization injection occurs when the peak amplitude exceeds
certain threshold. The threshold is exceeded for limited duration periodically
at different propagation distances, leading to multiple ionization injections
and separated electron bunches. The method is demonstrated through
multi-dimensional particle-in-cell simulations. Such electron bunches may be
used to generate multi-chromatic X-ray sources for a variety of applications.Comment: 5 pages, 5 figures; accepted by PR
Computed tomography imaging of early coronary artery lesions in stable individuals with multiple cardiovascular risk factors
OBJECTIVES: To investigate the prevalence, extent, severity, and features of coronary artery lesions in stable patients with multiple cardiovascular risk factors. METHODS: Seventy-seven patients with more than 3 cardiovascular risk factors were suspected of having coronary artery disease. Patients with high-risk factors and 39 controls with no risk factors were enrolled in the study. The related risk factors included hypertension, impaired glucose tolerance, dyslipidemia, smoking history, and overweight. The characteristics of coronary lesions were identified and evaluated by 64-slice coronary computed tomography angiography. RESULTS: The incidence of coronary atherosclerosis was higher in the high-risk group than in the no-risk group. The involved branches of the coronary artery, the diffusivity of the lesion, the degree of stenosis, and the nature of the plaques were significantly more severe in the high-risk group compared with the no-risk group (all p < 0.05). CONCLUSION: Among stable individuals with high-risk factors, early coronary artery lesions are common and severe. Computed tomography has promising value for the early screening of coronary lesions
Silicon nitride metalenses for unpolarized high-NA visible imaging
As one of nanoscale planar structures, metasurface has shown excellent
superiorities on manipulating light intensity, phase and/or polarization with
specially designed nanoposts pattern. It allows to miniature a bulky optical
lens into the chip-size metalens with wavelength-order thickness, playing an
unprecedented role in visible imaging systems (e.g. ultrawide-angle lens and
telephoto). However, a CMOS-compatible metalens has yet to be achieved in the
visible region due to the limitation on material properties such as
transmission and compatibility. Here, we experimentally demonstrate a divergent
metalens based on silicon nitride platform with large numerical aperture
(NA~0.98) and high transmission (~0.8) for unpolarized visible light,
fabricated by a 695-nm-thick hexagonal silicon nitride array with a minimum
space of 42 nm between adjacent nanoposts. Nearly diffraction-limit virtual
focus spots are achieved within the visible region. Such metalens enables to
shrink objects into a micro-scale size field of view as small as a single-mode
fiber core. Furthermore, a macroscopic metalens with 1-cm-diameter is also
realized including over half billion nanoposts, showing a potential application
of wide viewing-angle functionality. Thanks to the high-transmission and
CMOS-compatibility of silicon nitride, our findings may open a new door for the
miniaturization of optical lenses in the fields of optical fibers,
microendoscopes, smart phones, aerial cameras, beam shaping, and other
integrated on-chip devices.Comment: 16 pages, 7 figure
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