Quantum-dot gain without inversion:Effects of dark plasmon-exciton hybridization

We propose an initial-state-dependent quantum-dot gain without population inversion in the vicinity of a resonant metallic nanoparticle. The gain originates from the hybridization of a dark plasmon-exciton and is accompanied by efficient energy transfer from the nanoparticle to the quantum dot. This hybridization of the dark plasmon-exciton, attached to the hybridization of the bright plasmon-exciton, strengthens nonlinear light-quantum emitter interactions at the nanoscale, thus the spectral overlap between the dark and the bright plasmons enhances the gain effect. This hybrid system has potential applications in ultracompact tunable quantum devices.Physics, Condensed MatterSCI(E)[email protected]

Geological characteristics and main challenges of onshore deep oil and gas development in China

More than 30 years of continuous development has made onshore deep and ultra-deep conventional and unconventional oil and gas become an integral part of increasing the energy reserves and output by China’s petroleum industry. Based on the deep oil and gas geological conditions in the country, the present study finds that paleo stratum and deep burial are the two basic geological characteristics of deep oil and gas. Furthermore, we put forward the notion that it is necessary to strengthen the fundamental research of theories in four aspects and the core technology in five aspects of deep oil and gas. It is suggested that it is of special importance to promote the scientific and technological research of deep oil and gas through the scientific exploration of “myriameter deep” wells as the starting point, so as to boost the development of deep oil and gas field in China.Cited as: Yang, Z., Zou, C., Gu, Z., Yang, F., Li, J., Wang, X. Geological characteristics and main challenges of onshore deep oil and gas development in China. Advances in Geo-Energy Research, 2022, 6(3): 264-266. https://doi.org/10.46690/ager.2022.03.0

Bipartite Graph Pre-training for Unsupervised Extractive Summarization with Graph Convolutional Auto-Encoders

Pre-trained sentence representations are crucial for identifying significant sentences in unsupervised document extractive summarization. However, the traditional two-step paradigm of pre-training and sentence-ranking, creates a gap due to differing optimization objectives. To address this issue, we argue that utilizing pre-trained embeddings derived from a process specifically designed to optimize cohensive and distinctive sentence representations helps rank significant sentences. To do so, we propose a novel graph pre-training auto-encoder to obtain sentence embeddings by explicitly modelling intra-sentential distinctive features and inter-sentential cohesive features through sentence-word bipartite graphs. These pre-trained sentence representations are then utilized in a graph-based ranking algorithm for unsupervised summarization. Our method produces predominant performance for unsupervised summarization frameworks by providing summary-worthy sentence representations. It surpasses heavy BERT- or RoBERTa-based sentence representations in downstream tasks.Comment: Accepted by the 2023 Conference on Empirical Methods in Natural Language Processing (EMNLP 2023

Whole-Genome Sequencing Of Mesorhizobium huakuii 7653R Provides Molecular Insights into Host Specificity and Symbiosis Island Dynamics

Background Evidence based on genomic sequences is urgently needed to confirm the phylogenetic relationship between Mesorhizobium strain MAFF303099 and M. huakuii. To define underlying causes for the rather striking difference in host specificity between M. huakuii strain 7653R and MAFF303099, several probable determinants also require comparison at the genomic level. An improved understanding of mobile genetic elements that can be integrated into the main chromosomes of Mesorhizobium to form genomic islands would enrich our knowledge of how genome dynamics may contribute to Mesorhizobium evolution in general. Results In this study, we sequenced the complete genome of 7653R and compared it with five other Mesorhizobium genomes. Genomes of 7653R and MAFF303099 were found to share a large set of orthologs and, most importantly, a conserved chromosomal backbone and even larger perfectly conserved synteny blocks. We also identified candidate molecular differences responsible for the different host specificities of these two strains. Finally, we reconstructed an ancestral Mesorhizobium genomic island that has evolved into diverse forms in different Mesorhizobium species. Conclusions Our ortholog and synteny analyses firmly establish MAFF303099 as a strain of M. huakuii. Differences in nodulation factors and secretion systems T3SS, T4SS, and T6SS may be responsible for the unique host specificities of 7653R and MAFF303099 strains. The plasmids of 7653R may have arisen by excision of the original genomic island from the 7653R chromosome

General approach for preparing sandwich-structured metal sulfide@reduced graphene oxide as highly reversible Li-ion battery anode

A general method for preparing sandwiched nanostructures consisting of reduced graphene oxide (rGO) and metal sulfides is presented. As a demonstrating example, the sandwiched MoS2@rGO nanocomposites show a good electrochemical performance including a high reversible capability of 1345 mAh g−1 at 0.5 A g−1 over 400 cycles, and a superior rate performance. Moreover, this method has been verified to fabricate a large set of transition metal sulfides- and double metal sulfides-based rGO composites such as CoS@rGO, NiS@rGO, NiCo2S4@rGO, and CuCo2S4@rGO, enabling the preparing approach presented here applicable for many possible anode and cathode chemistries. Impact statement A general strategy for the fabrication of sandwiched nanostructures consisting of reduced graphene oxide (rGO) and metal sulfides for highly reversible Li-ion battery anode has been developed

Experimental Study on the Bonding Performance between Fiber-Belt-Bar and Concrete

Fiber materials have advantages such as light weight and high strength, corrosion resistance, fatigue resistance, and easy processing and production, and they are widely applied in the repair and renovation of concrete structures. To promote the construction convenience of fiber materials, fiber raw yarn is continuously braided to form fiber-belt-bars. Based on the existing research, the performance of bonding between fiber-belt-bars and a concrete interface was investigated, and pull-out tests were performed to systematically investigate the effects of the fiber-belt-bar cross-sectional size, anchorage length, concrete strength, and fiber type on the bonding performance. The experimental results show that the bond strength reduces with an increase in the anchorage length, increase in cross-sectional size, and decrease in concrete strength, and the effect of fiber type on the bond strength is not obvious. On this basis, a formula for calculating the average bond strength of fiber-belt-bars is proposed. Experiments and calculations determined that the average bond strength between fiber-belt-bar and concrete with a cross-sectional size of 12 mm × 3 mm is 10–30% higher than that with a cross-sectional size of 20 mm × 3 mm for the same anchorage length. Finally, the minimum anchorage length of the fiber-belt-bar is proposed to provide a valuable reference for the use of fiber-belt-bar in concrete projects

Damage Evaluation of Concrete under Uniaxial Compression Based on the Stress Dependence of AE Elastic Wave Velocity Combined with DIC Technology

This study presented evaluation of a concrete damage process by the acoustic emission (AE) technique under uniaxial multi-step compressive loading procedure combined with digital image correlation (DIC). The results showed that AE elastic wave velocity had good stress dependence in the damage process of concrete specimens with different sizes (cube, prism) and coarse aggregate characteristics (volume fraction, maximum size), and the effects of specimen sizes and coarse aggregate characteristics on the stress dependence can be nearly neglected. The standard deviation of 32 AE elastic wave velocities was used as the criterion to evaluate the relative stress ratio of concrete under different damage states, and the damage process of concrete was divided into three damage stages according to this criterion. When the standard deviation is below 70, in the range of 70 to 1700, and greater than 1700, the concrete damage process is defined as steady damage process, accelerated damage process and buckling damage process, respectively. The accuracy of the presented evaluation methodology was demonstrated by comparative results with digital image correlation. The results indicate that the standard deviation of AE elastic wave velocities can potentially serve as a reliable, convenient, and non-destructive evaluation criterion of concrete damage state under uniaxial compressive loading

Performance Simulation of Solar Trough Concentrators: Optical and Thermal Comparisons

The solar trough concentrator is used to increase the solar radiation intensity on absorbers for water heating, desalination, or power generation purposes. In this study, optical performances of four solar trough concentrators, viz. the parabolic trough concentrator (PTC), the compound parabolic concentrator (CPC), the surface uniform concentrator (SUC), and the trapezoid trough concentrator (TTC), are simulated using the Monte Carlo Ray Tracing method. Mathematical models for the solar trough concentrators are first established. The solar radiation distributions on their receivers are then simulated. The solar water heating performances using the solar trough concentrators are finally compared. The results show that, as a high-concentration ratio concentrator, the PTC can achieve the highest heat flux, but suffers from the worst uniformity on the absorber, which is only 0.32%. The CPC can generate the highest heat flux among the rest three low-concentration ratio solar trough concentrators. Compared with the PTC and the CPC, the TTC has better uniformity, but its light-receiving ratio is only 70%. The SUC is beneficial for its highest uniformity of 87.38%. Thermal analysis results show that the water temperatures inside the solar trough concentrators are directly proportional to their wall temperature, with the highest temperature rise in the PTC and the smallest temperature rise in the TTC. The solar trough concentrators’ thermal deformations are positively correlated to their wall temperatures. The radial deformation of the SUC is much larger than those of other solar trough concentrators. The smallest equivalent stress is found in the SUC, which is beneficial to the long-term operation of the solar water heating system