Fast and High-Performance Learned Image Compression With Improved Checkerboard Context Model, Deformable Residual Module, and Knowledge Distillation

Deep learning-based image compression has made great progresses recently. However, many leading schemes use serial context-adaptive entropy model to improve the rate-distortion (R-D) performance, which is very slow. In addition, the complexities of the encoding and decoding networks are quite high and not suitable for many practical applications. In this paper, we introduce four techniques to balance the trade-off between the complexity and performance. We are the first to introduce deformable convolutional module in compression framework, which can remove more redundancies in the input image, thereby enhancing compression performance. Second, we design a checkerboard context model with two separate distribution parameter estimation networks and different probability models, which enables parallel decoding without sacrificing the performance compared to the sequential context-adaptive model. Third, we develop an improved three-step knowledge distillation and training scheme to achieve different trade-offs between the complexity and the performance of the decoder network, which transfers both the final and intermediate results of the teacher network to the student network to help its training. Fourth, we introduce $L_{1}$ regularization to make the numerical values of the latent representation more sparse. Then we only encode non-zero channels in the encoding and decoding process, which can greatly reduce the encoding and decoding time. Experiments show that compared to the state-of-the-art learned image coding scheme, our method can be about 20 times faster in encoding and 70-90 times faster in decoding, and our R-D performance is also $2.3 \%$ higher. Our method outperforms the traditional approach in H.266/VVC-intra (4:4:4) and some leading learned schemes in terms of PSNR and MS-SSIM metrics when testing on Kodak and Tecnick-40 datasets.Comment: Submitted to Trans. Journa

Spatiotemporal Changes of China's Carbon Emissions

Spatiotemporal changes in China's carbon emissions during the 11th and 12th Five‐Year Plan periods are quantified for the first time through a reconstructed nationwide high‐resolution gridded data set. The hot spots of carbon emissions in China have expanded by 28.5% (toward the west) in the north and shrunk by 18.7% in the south; meanwhile, the emission densities in North and South China have increased by 15.7% and 49.9%, respectively. This suggests a clear transition to a more intensive economic growth model in South China as a result of the energy conservation and emission reduction policies, while the expanded carbon hot spots in North China are mainly dominated by the Grand Western Development Program. The results also show that China's carbon emissions exhibit a typical spatially intensive, high‐emission pattern, which has undergone a slight relaxation (up to 3%) from 2007 to 2012 due to a typical urbanization process

On a Kind of Dirichlet Character Sums

Let p≥3 be a prime and let χ denote the Dirichlet character modulo p. For any prime q with q<p, define the set Eq,p=a∣1≤a,a-≤p,aa-≡1modp  and  a≡a-modq. In this paper, we study a kind of mean value of Dirichlet character sums ∑a≤p  a∈Eq,pχ(a), and use the properties of the Dirichlet L-functions and generalized Kloosterman sums to obtain an interesting estimate

Nanoconfined Water Effect on CO2 Utilization and Geological Storage

Understanding nanoconfined water effect on CO2 utilization and storage has tremendous implications in academic research and practical applications, especially for extremely low‐permeability shale reservoirs. Here, a new nanoscale‐extended cubic‐plus association equation of state is developed by including the confinement effects and intermolecular interactions, based on which the phase behavior and interfacial tension of the pure water and water‐CO2 system are accurately calculated. Moreover, three important parameters, caprock‐sealing pressure, maximum storage height, and storage capacity, are quantitatively determined for assessing the potential for the CO2 storage. On the basis of the results from this study, the negative effect of nanoconfiend water can be substantially reduced or even converted to be positive for the CO2 utilization and storage in the shale reservoirs due to the extremely small pore scale as well as the associated strong confinements and intermolecular interactions. Overall, this study supports the foundation of general practical applications pertaining to CO2 utilization and geological storage in unconventional low‐permeability shale formations with existence of nanoconfined water.Plain Language SummaryCO2 utilization and geological storage is an emerging topic in energy and environmental community. Nanoconfined water, either from the natural connate or anthropogenic injected/residual source, is an inevitable topic for CO2 utilizations and storages in geological media. However, most existing theories/methodologies specialized in CO2 utilization and geological storage are restricted to the conventional large‐scale porous media without water effect, which may lose effectiveness/accuracy for extremely confined geological media, for example, shale formations. On the other hand, supplies of geological sites with conventional pore scale are badly limited; meanwhile, abundant geological media with unconventional extremely small pores are available and appropriate for CO2 utilization and storage worldwide. This study initially proposes a theoretical method to characterize the CO2 utilization and geological storage at the nanometer scale and investigate the associated nanoconfined water effect. Qualitative and quantitative analyses fill the knowledge gap of the nanoscale water and CO2 behavior. Also, solid scientific results/supports from this study are provided for various academic researches and practical applications, such as the energy and environment and biotechnologies. Therefore, as a comprehensive work consisting of fundamental research and practical applications, this paper shares a wide readership on the areas of science and engineering concurrently.Key PointsThis study initializes CO2 utilization and geological storage at the nanometer scale and associated nanoconfined water effectsQualitative and quantitative analyses fill the knowledge gap of the nanoscale water and CO2 systemsSolid scientific knowledge from this study provides technical supports for various future academic research and practical application

ROTATIONALLY RESOLVED ION DIP SPECTROSCOPY OF NH3 (X)over-tilde ->(C)over-tilde'->(A)over-tilde TRANSITIONS

Ion dip spectroscopy, a folded OODR process with ion detection, has hitherto only been applied to the study of high lying vibrational levels of ground state polyatomics, We have succeeded in employing this technique to obtain rotationally resolved spectra of NH, (A) over tilde (1)A ''(2), a fast predissociating species. Conceivably, the method can be generalized to deal with a large number of other predissociating species

Ecological network analysis of an energy metabolism system based on input-output tables: Model development and case study for Guangdong

Rapid urbanization results in energy shortage and unreasonable energy metabolism structure. The goal of this research is to take Guangdong, China as a special case study to illustrate the influence of energy classification differences on the energy metabolism system. To do so, we introduced the concept of “urban metabolism”, and treated sectors and energy flows as nodes and paths in a network model. We used the input output analysis to compile the physical input output table through the embodied energy element intensity. Building on this, we used ecological network analysis to quantify the urban metabolic processes and energy metabolism levels within the urban system. In addition, the alternative indicators are first introduced to explore the best alternative energy in various sectors to avoid a short-term energy crisis. In this paper, different energy groups are considered on the energy metabolism system, including all energy, primary energy, secondary energy and six specific energy, which will fill the research gap about the influence of energy classification on urban energy metabolism. It is found that the energy metabolism of Guangdong is now in the state of sub-health. The energy metabolism hierarchy atlas shows that the pulling force is hardly affected by the energy classification but the driving force is very sensitive, which further illustrate that producers can choose different energy according to their production structure. Facing the shortage of energy supply, the secondary energy with the highest substitutability of all energy value is the better alternative energy for advanced manufacturing sector (containing twelve industries such as Manufacture of transportation equipment and Manufacture of metal products). More specifically, the nonrenewable properties of primary energy make it particularly important to find the corresponding alternative energy. Heat is the best alternative energy for crude oil, while electricity is irreplaceable. It is expected that the results will provide scientific support to guide the reform of urban energy metabolic system in an attempt to coordinate the energy development strategy, improve the energy consumption structure and maintain energy security and stability