177 research outputs found
Towards Hybrid-Optimization Video Coding
Video coding is a mathematical optimization problem of rate and distortion
essentially. To solve this complex optimization problem, two popular video
coding frameworks have been developed: block-based hybrid video coding and
end-to-end learned video coding. If we rethink video coding from the
perspective of optimization, we find that the existing two frameworks represent
two directions of optimization solutions. Block-based hybrid coding represents
the discrete optimization solution because those irrelevant coding modes are
discrete in mathematics. It searches for the best one among multiple starting
points (i.e. modes). However, the search is not efficient enough. On the other
hand, end-to-end learned coding represents the continuous optimization solution
because the gradient descent is based on a continuous function. It optimizes a
group of model parameters efficiently by the numerical algorithm. However,
limited by only one starting point, it is easy to fall into the local optimum.
To better solve the optimization problem, we propose to regard video coding as
a hybrid of the discrete and continuous optimization problem, and use both
search and numerical algorithm to solve it. Our idea is to provide multiple
discrete starting points in the global space and optimize the local optimum
around each point by numerical algorithm efficiently. Finally, we search for
the global optimum among those local optimums. Guided by the hybrid
optimization idea, we design a hybrid optimization video coding framework,
which is built on continuous deep networks entirely and also contains some
discrete modes. We conduct a comprehensive set of experiments. Compared to the
continuous optimization framework, our method outperforms pure learned video
coding methods. Meanwhile, compared to the discrete optimization framework, our
method achieves comparable performance to HEVC reference software HM16.10 in
PSNR
DynImp: Dynamic Imputation for Wearable Sensing Data Through Sensory and Temporal Relatedness
In wearable sensing applications, data is inevitable to be irregularly
sampled or partially missing, which pose challenges for any downstream
application. An unique aspect of wearable data is that it is time-series data
and each channel can be correlated to another one, such as x, y, z axis of
accelerometer. We argue that traditional methods have rarely made use of both
times-series dynamics of the data as well as the relatedness of the features
from different sensors. We propose a model, termed as DynImp, to handle
different time point's missingness with nearest neighbors along feature axis
and then feeding the data into a LSTM-based denoising autoencoder which can
reconstruct missingness along the time axis. We experiment the model on the
extreme missingness scenario ( missing rate) which has not been widely
tested in wearable data. Our experiments on activity recognition show that the
method can exploit the multi-modality features from related sensors and also
learn from history time-series dynamics to reconstruct the data under extreme
missingness.Comment: 5 pages, 2 figures, accepted in ICASSP'202
Stability of a Two-Strain Tuberculosis Model with General Contact Rate
A two-strain tuberculosis model with general contact rate which allows tuberculosis patients with the drug-sensitive Mycobacterium tuberculosis strain to be treated is presented.
The model includes both drug-sensitive and drug-resistant strains. A detailed qualitative
analysis about positivity, boundedness, existence, uniqueness and global stability of the equilibria of this model is carried out. Analytical results of the model show that the quantities
R1 and R2, which represent the basic reproduction numbers of the sensitive and resistant
strains, respectively, provide the threshold conditions which determine the competitive outcomes of the two strains. Numerical simulations are also conducted to confirm and extend
the analytic results
Reflection of Russian and Chinese University Students on Entrepreneurial Intention
Entrepreneurship is nowadays an appealing topic for researchers to investigate. It is considered to be an agent for social and economic development. Most of the countries has included entrepreneurship as core subject in curricula of schools, colleges and universities. To involve youth in entrepreneurship and pr ovide them opportunity to use their knowledge, skills and abilities to solve real world p roblems is the need of current era. This paper explains Chinese and Russian universities students’ intention towards entrepr eneurship. Theory of Planned behavior (TPB) were used for theoretical frame work of the study. Along 118 XII Международная конференция «Российские регионы в фокусе перемен» with variables attitude towards entrepreneurship, subjective norm and perceived behavioral control from (TPB) entrepreneurial environment and education as contextual predictor were found significant in i mpact on students’ entrepreneurial intention. Findings suggest that more attention is needed from policy makers to involve youth in entrepreneurship
The Flare and Warp of the Young Stellar Disk traced with LAMOST DR5 OB-type stars
We present analysis of the spatial density structure for the outer disk from
814 \,kpc with the LAMOST DR5 13534 OB-type stars and observe similar
flaring on north and south sides of the disk implying that the flaring
structure is symmetrical about the Galactic plane, for which the scale height
at different Galactocentric distance is from 0.14 to 0.5 \,kpc. By using the
average slope to characterize the flaring strength we find that the thickness
of the OB stellar disk is similar but flaring is slightly stronger compared to
the thin disk as traced by red giant branch stars, possibly implying that
secular evolution is not the main contributor to the flaring but perturbation
scenarios such as interactions with passing dwarf galaxies should be more
possible. When comparing the scale height of OB stellar disk of the north and
south sides with the gas disk, the former one is slightly thicker than the
later one by 33 and 9 \,pc, meaning that one could tentatively use
young OB-type stars to trace the gas properties. Meanwhile, we unravel that the
radial scale length of the young OB stellar disk is 1.17 0.05 \,kpc,
which is shorter than that of the gas disk, confirming that the gas disk is
more extended than stellar disk. What is more, by considering the mid-plane
displacements () in our density model we find that almost all of
are within 100 \,pc with the increasing trend as Galactocentric distance
increases.Comment: 14 pages and 8 figures, Accepted by APJ for publicatio
Constructing Heterostructure through Bidentate Coordination toward Operationally Stable Inverted Perovskite Solar Cells
It has been reported that one of the influencing factors leading to stability issues in iodine-containing perovskite solar cells is the iodine loss from the perovskite layer. Herein, bidentate coordination is used with undercoordinated I− of the perovskite surface to construct the stable perovskite-based heterostructure. This strong halogen bonding effectively inhibits interfacial migration of I− into functional layers such as C60 and Ag. Moreover, passivation of the undercoordinated I− suppresses the release of I2 and further delays the formation of voids at the perovskite surface. The resulting inverted perovskite solar cell exhibits a power conversion efficiency of 22.59% and the unencapsulated device maintains 96.15% of its initial value after continuous operation for 500 h under illumination.journal articl
A novel regional irrigation water productivity model coupling irrigation- and drainage-driven soil hydrology and salinity dynamics and shallow groundwater movement in arid regions in China
The temporal and spatial distributions of regional irrigation water productivity (RIWP) are crucial for making decisions related to agriculture, especially in arid irrigated areas with complex cropping patterns. Thus, in this study, we developed a new RIWP model for an irrigated agricultural area with complex cropping patterns. The model couples the irrigation- and drainage-driven soil water and salinity dynamics and shallow groundwater movement in order to quantify the temporal and spatial distributions of the target hydrological and biophysical variables. We divided the study area into 1 km x 1 km hydrological response units (HRUs). In each HRU, we considered four land use types: sunflower fields, wheat fields, maize fields, and uncultivated lands (bare soil). We coupled the regional soil hydrological processes and groundwater flow by taking a weighted average of the water exchange between unsaturated soil and groundwater under different land use types. The RIWP model was calibrated and validated using 8 years of hydrological variables obtained from regional observation sites in a typical arid irrigation area in North China, the Hetao Irrigation District. The model simulated soil moisture and salinity reasonably well as well as groundwater table depths and salinity. However, overestimations of groundwater discharge were detected in both the calibration and validation due to the assumption of well-operated drainage ditch conditions; regional evapotranspiration (ET) was reasonably estimated, whereas ET in the uncultivated area was slightly underestimated in the RIWP model. A sensitivity analysis indicated that the soil evaporation coefficient and the specific yield were the key parameters for the RIWP simulation. The results showed that the RIWP decreased from maize to sunflower to wheat from 2006 to 2013. It was also found that the maximum RIWP was reached when the groundwater table depth was between 2 and 4 m, regardless of the irrigation water depth applied. This implies the importance of groundwater table control on the RIWP. Overall, our distributed RIWP model can effectively simulate the temporal and spatial distribution of the RIWP and provide critical water allocation suggestions for decision-makers.This research has been supported by the National Key Research and Development Program of China (grant no. 2017YFC0403301), the National Natural Science Foundation of China (grant nos. 51679236 and 51639009), and the International Postdoctoral Exchange Fellowship Program from the Office of China Postdoctoral Council (grant no. 20180044)
Comparison among Reconstruction Algorithms for Quantitative Analysis of 11
Objective. Kinetic modeling of dynamic 11C-acetate PET imaging provides quantitative information for myocardium assessment. The quality and quantitation of PET images are known to be dependent on PET reconstruction methods. This study aims to investigate the impacts of reconstruction algorithms on the quantitative analysis of dynamic 11C-acetate cardiac PET imaging. Methods. Suspected alcoholic cardiomyopathy patients (N=24) underwent 11C-acetate dynamic PET imaging after low dose CT scan. PET images were reconstructed using four algorithms: filtered backprojection (FBP), ordered subsets expectation maximization (OSEM), OSEM with time-of-flight (TOF), and OSEM with both time-of-flight and point-spread-function (TPSF). Standardized uptake values (SUVs) at different time points were compared among images reconstructed using the four algorithms. Time-activity curves (TACs) in myocardium and blood pools of ventricles were generated from the dynamic image series. Kinetic parameters K1 and k2 were derived using a 1-tissue-compartment model for kinetic modeling of cardiac flow from 11C-acetate PET images. Results. Significant image quality improvement was found in the images reconstructed using iterative OSEM-type algorithms (OSME, TOF, and TPSF) compared with FBP. However, no statistical differences in SUVs were observed among the four reconstruction methods at the selected time points. Kinetic parameters K1 and k2 also exhibited no statistical difference among the four reconstruction algorithms in terms of mean value and standard deviation. However, for the correlation analysis, OSEM reconstruction presented relatively higher residual in correlation with FBP reconstruction compared with TOF and TPSF reconstruction, and TOF and TPSF reconstruction were highly correlated with each other. Conclusion. All the tested reconstruction algorithms performed similarly for quantitative analysis of 11C-acetate cardiac PET imaging. TOF and TPSF yielded highly consistent kinetic parameter results with superior image quality compared with FBP. OSEM was relatively less reliable. Both TOF and TPSF were recommended for cardiac 11C-acetate kinetic analysis
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