EventDrop: data augmentation for event-based learning

The advantages of event-sensing over conventional sensors (e.g., higher dynamic range, lower time latency, and lower power consumption) have spurred research into machine learning for event data. Unsurprisingly, deep learning has emerged as a competitive methodology for learning with event sensors; in typical setups, discrete and asynchronous events are first converted into frame-like tensors on which standard deep networks can be applied. However, over-fitting remains a challenge, particularly since event datasets remain small relative to conventional datasets (e.g., ImageNet). In this paper, we introduce EventDrop, a new method for augmenting asynchronous event data to improve the generalization of deep models. By dropping events selected with various strategies, we are able to increase the diversity of training data (e.g., to simulate various levels of occlusion). From a practical perspective, EventDrop is simple to implement and computationally low-cost. Experiments on two event datasets (N-Caltech101 and N-Cars) demonstrate that EventDrop can significantly improve the generalization performance across a variety of deep networks.Comment: IJCAI 202

Observation of Universal Expansion Anisotropy from Cold Atoms to Hot Quark-Gluon Plasma

Azimuthal anisotropy has been ubiquitously observed in high-energy proton-proton, proton-nucleus, and nucleus-nucleus (heavy-ion) collisions, shaking the early belief that those anisotropies must stem from utterly strong interactions. This work reports a study of anisotropic expansion of cold $^{6}$Li Fermi gases, initially trapped in an anisotropic potential, as a function of the interaction strength that can be readily tuned by an external magnetic field. It is found that the expansion anisotropy builds up quickly at small interaction strength, without the need of utterly strong interactions. A universal behavior of the expansion anisotropy is quantitatively observed between cold-atom and heavy-ion systems, despite their vast differences in physics. This universality will potentially unify a variety of disciplines in nature, from the weakly interacting dilute systems of gases to the strongly interacting quark-gluon plasma of the early universe.Comment: 11 pages, 11 figure

Spatial scale effect of surface routing and its parameter upscaling for urban flood simulation using a grid‐based model

Urban catchments are characterized by a wide variety of complex juxtapositions and surface compositions that are linked to multiple overland flow paths. Their extremely high spatial heterogeneity leads to great sensitivity of hydrologic simulation to the scale variation of calculation units. Although extensive efforts have been made for investigating the scale effects and indicate its significance, less is understood of how routing features vary with spatial scales and further how the variation of routing features influences the hydrological response. In this paper, a grid-based distributed urban hydrological model is applied to study spatial scale effects ranging from 10 to 250 m. Two parameters are proposed to quantitatively depict the routing features of overland flow specified for impervious and pervious areas. The results show that routing features are quite sensitive to spatial resolution. Large differences among simulations exist in the infiltration amounts attributed to the combined effects of the two routing parameters, which leads to opposite effects for both total flow volume and peak flow for various rainfall events. The relationship of the key model parameters at different spatial resolutions can be explicitly expressed by corresponding routing features. With this relationship, parameters transfer among different spatial scales can be realized to obtain consistent simulation results. This study further revealed the quantitative relationship between spatial scales, routing features and the hydrologic processes, and enabled accurate and efficient simulations required by real time flooding forecasting and land-atmosphere coupling, while fully taking the advantages of detailed surface information. Plain Language Summary Given the inherent complex underlying surface compositions and overland flow paths in urban areas, underlying high spatial resolution surface data eventually become necessary. Unfortunately, high resolution modelling in urban catchment is still challenging in terms of computational restricts, proper setting up of parameters etc., due to the high spatial heterogeneity. Practical simulation requirements often limit the use of high resolution models, as in the case of real time prediction of urban flooding, the coupling of land-atmosphere processes. Therefore, it is necessary to investigate the scale effects and its mechanism, and then to explore an accommodation approach to enable precise flooding prediction with a coarse model. For grid-based and distributed hydrologic models, the mosaic method can basically eliminate the scale effects on the runoff generation process. However, the scale effects on overland flow routing remain insufficiently understood, and to help understand the scale effects, simulations were performed under five different resolutions, ranging from 10 m to 250 m, for various rainfall events. Two physical parameters are introduced to quantify the scale effects on routing features. Three variables are concurrently calculated to assess the effects on modeling outputs. The results indicate that routing features are sensitive to changes in spatial resolution, which results in opposite effects on simulation results under different rainfall conditions. In conclusion, an accommodation approach is proposed based on the affecting mechanism

Factors influencing successful establishment of exotic Pinus radiata seedlings with co-introduced Lactarius deliciosus or local ectomycorrhizal fungal communities

An introduction of exotic or non-native trees may fail due to a lack of suitable fungal partners. We planted exotic Pinus radiata in Xifeng, Guizhou Southwest China. Strategies to introduce P. radiata seedlings either colonized with an ectomycorrhizal fungus (EcMF), Lactarius deliciosus, or expect them to form familiar/new associations with local EcMF in a new habitat were studied to know how P. radiata could be successfully established over a period of 2.5 years. Plant height and needle nutrient acquisition, the persistence of the co-introduced L. deliciosus, and fungal community composition in rhizosphere soil and root tips were analyzed. In addition, a greenhouse bioassay experiment of local soil to assess the differences in the EcMF community between exotic and native pine seedlings was also conducted. The current results demonstrated that P. radiata could establish in the Xifeng plantation with or without co-introduced L. deliciosus. The co-introduced L. deliciosus might be naturalized with P. radiata in the new area since it has been fruited for 2 years with high relative abundance in mycorrhizosphere soil. L. deliciosus pre-colonization significantly altered the mycorrhizosphere fungal composition and it had a positive correlation with nitrogen acquisition of P. radiata. Host identity had no effect on fungal composition since exotic P. radiata and native P. massoniana recruited similar local fungal communities in early establishment or in plantation. The cosmopolitan species Suillus placidus, with high relative abundance, formed a familiar association with P. radiata. The greenhouse bioassay experiment further showed that Suillus sp. contributed relatively higher total extracellular enzymes by forming ectomycorrhizas with P. radiata and the same type of ectomycorrhiza of P. radiata and P. massoniana showed different enzymatic functions. Our study indicated that exotic P. radiata could be a suitable tree capable to get established successfully in the Xifeng plantation either by interaction with the co-introduced L. deliciosus or with a local EcMF, but we should be cautious about large-scale planting of P. radiata. L. deliciosus persisted in plantation and more attention should be paid to local EcMF community changes induced by the introduced L. deliciosus.This work was supported by the Fund of Yunnan Key Laboratory for Fungal Diversity and Green Development (No. E03A311261-6), the National Sciences Foundation of China (No. 31901204), and the Yunnan Key Project of Science and Technology (No. 202102AE090034)

Effects of Aromatic Ammoniums on Methyl Ammonium Lead Iodide Hybrid Perovskite Materials

The introduction of bulky ammoniums into methyl ammonium lead iodide hybrid perovskites (MAPbI3) has emerged as a promising strategy to improve the properties of these materials. In the present work, we studied the effects of several aromatic ammoniums onto the structural, electronic, and optical properties of MAPbI3. Although powder XRD data suggest that the bulky cations are not involved in the bulk phase of the MAPbI3, a surprisingly large effect of the bulky cations onto the photoluminescence properties was observed

Ethnomycological study on wild mushrooms in Pu’er Prefecture, Southwest Yunnan, China

Abstract Background: Yunnan is rich in fungal diversity and cultural diversity, but there are few researches on ethnomycology. In addition, extensive utilization of wild edible fungi (WEF), especially the ectomycorrhizal fungi, threatens the fungal diversity. Hence, this study aims to contribute to the ethnomycological knowledge in Pu’er Prefecture, Yunnan, China,including information on the fungal taxa presented in markets and natural habitats, with emphasis in ectomycorrhizal fungi (EMF). Methods: Semi-structured interviews with mushroom vendors in markets and with mushroom collectors in natural habitats were conducted. Information related to local names, habitat, fruiting time, species identifcation, price, cooking methods and preservation methods of wild edible mushrooms were recorded. Wild edible fungi were collected from forests, and morphological and molecular techniques were used to identify fungal species. Results: A total of 11 markets were visited during this study. The 101 species collected in the markets belonged to 22 families and 39 genera, and about 76% of them were EMF. A wealth of ethnomycological knowledge was recorded, and we found that participants in the 45–65 age group were able to judge mushroom species more accurately. Additionally, men usually had a deepest mushroom knowledge than women. A total of 283 species, varieties and undescribed species were collected from natural habitats, and about 70% of them were EMF. Mushroom species and recorded amounts showed correspondence between markets and the natural habitats on diferent months. Conclusion: The present study shows that Pu’er Prefecture is rich in local mycological knowledge and fungal diversity. However, it is necessary to continue the research of ethnomycological studies and to design and conduct dissemination of local knowledge in order to preserve it, since it currently remains mainly among the elderly population.This work was supported by the International (Regional) Cooperation and Exchange Projects of the National Natural Science Foundation of China (No. 31961143010) and the open research project of the “Cross-Cooperative Team” of the Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences

Blind source separation communication anti-jamming technology and practice

Aiming at the threat of broad frequency band suppressing jamming and the inherent contradiction between spectrum resources and communication anti-jamming ability, a method was proposed to add the statistics domain dimension on the basis of spread spectrum anti-jamming, which promoted the transformation of communication anti-jamming from hard anti-jamming to accommodate the jamming.The statistical characteristics difference between communication signal and jamming signal was utilized by blind source separation (BSS) communication anti-jamming technology to separate signals, which could improve the communication anti-jamming ability without increasing spectrum resources.To understand and improve the development process of BSS communication anti-jamming (BSSCA) from theory and algorithm to engineering practice, the basic principle of BSSCA was described, the key technologies such as multi-channel BSS and single channel BSS were emphasized.The main characteristics and existing problems of BSSCA were analyzed.Finally, the development priorities of this field were pointed out