Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Overview of Position Servo Control Technology and Development of Voice Coil Motor

Voice coil motor (VCM) is a special direct drive linear motor, which can convert electric energy directly into mechanical energy without the use of transmission mechanism. VCM has the advantages of simple structure, good rigidity, fast response, silence, high linearity, no cogging force, no pulsation et al. It is widely used in the field of high-precision control. This paper reviews and summarizes the results of VCM research conducted by scholars from various countries, and summarizes the general situation of VCM servo control technology. Firstly, a basic description of VCM's mathematical model and common control mechanisms is provided. The benefits, drawbacks, and application of control techniques in the field of VCM are all explored in detail; At the same time, the methods to improve control strategy are proposed; Then, combined with the analysis and research of scholars in various countries on VCM, the problems of difficult to establish accurate model, friction disturbance and mechanical vibration of VCM and the solutions to the corresponding problems are summarized; Finally, a summary of VCM's application fields is provided

Asymmetric effects of litter accumulation on soil temperature and dominant plant species in fenced grasslands

Excess litter accumulates on the soil surface of fenced grasslands and alters the abiotic environment and plant population dynamics. However, little is known about the effect of litter accumulation on the interaction between environmental factors and plant population characteristics in fenced grasslands, especially over different time scales. We applied a three-year litter removal experiment to two kinds of fenced grasslands in Inner Mongolia, China. We measured soil temperature in situ and plant phenology and population characteristics of three dominant species (Stipa grandis, S. krylovii, and Leymus chinensis). During the growing season, litter accumulation (i.e., the control) significantly decreased soil temperature, with a larger effect in the daytime than at night. The diurnal negative effect gradually weakened across the growing season, whereas the negative effect in the nighttime shifted to a positive effect on soil temperature in the late growing season. The decreased soil temperature delayed plant phenology, with longer delays in S. grandis and S. krylovii than L. chinensis. Litter accumulation also significantly increased the height, cover, root biomass, and relative dominance of L. chinensis but decreased cover, density, root biomass, and relative dominance of both Stipa, driving replacement of S. grandis or S. krylovii by L. chinensis in two grasslands. Our findings emphasize the critical function of litter in grassland management and provide a new insight to elucidating the mechanism of how litter accumulation regulates the abiotic environment, community composition and structure, and successional change in fenced grasslands

Vegetation classification of Stipa steppes in China, with reference to the International Vegetation Classification

Aims: The vegetation classification system of China (China-VCS) is not completed. Stipa steppes are the most important steppes in China. Here we made optimal use of available plot data to classify Stipa steppes into associations in a way that is consistent with International Vegetation Classification. Study Area: the Songnen Plain, Inner Mongolian Plateau, Loess Plateau, Tibetan Plateau, and the northwest mountain areas of China. Methods: We used 1337 plots to partition the Stipa steppes of China into clusters using hierarchical clustering. Supervised noise clustering was used to improve the classifications at the group, alliance, and association levels. Non-metric multidimensional scaling ordination was used to visualize the homogeneity of plots within each cluster, and we overlaid site and climatic vectors. Diagnostic species were identified for each cluster using Indicator Species Analysis. Results: We defined five biogeographic groups, 26 alliances, 91 associations, and 12 communities of Stipa steppes of China. The Stipa-dominated alliances in the framework of the current China-VCS were verified, but the four vegetation subformations of Tussock Steppe were not completely supported by this study. Conclusions: This is the first systematical and comprehensive classification for Stipa steppes in China based on plot data. Our classification used a set of dominant species and diagnostic species to define biogeogrpahic groups, alliances and associations, ensuring compatibility with the International Vegetation Classification. Taxonomic reference: Flora Reipublicae Popularis Sinicae, Flora of China Abbreviations: AMT = Annual Mean Temperature; AP = Annual Precipitation; China-VCS = vegetation classification system of China; IVC = international vegetation classification; MTCQ = Mean Temperature of Coldest Quarter; MTWQ = Mean Temperature of Warmest Quarter; NC = noise clustering; NMDS = non-metric multidimensional scaling; PDQ = Precipitation of Driest Quarter; PS = Precipitation Seasonality; PWQ = Precipitation of Wettest Quarter; TS = Temperature Seasonalit

Litter accumulation alters the abiotic environment and drives community successional changes in two fenced grasslands in Inner Mongolia

Fencing is an effective and practical method for restoring degraded grasslands in northern China. However, little is known about the role of excess litter accumulation due to long-term fencing in regulating abiotic environment and driving changes in community structure and function. We conducted a three-year field experiment in two fenced grasslands in Inner Mongolia, and monitored light quantity, soil temperature, and soil moisture continuously, and determined community height, community aboveground net primary productivity (ANPP), and the relative dominance of different plant functional groups. Litter accumulation reduced light quantity and soil temperature but increased soil moisture. The regulating effects of litter accumulation on soil temperature and soil moisture fluctuated temporally and gradually weakened over the growing season. Litter accumulation also altered community vertical structure and function by increasing community height and ANPP. The increase in soil moisture increased the relative dominance of rhizome grasses but suppressed bunch grasses, thereby shifting bunch grass grasslands to rhizome grass grasslands. Our findings provide a potential mechanism for community succession in the context of litter accumulation in fenced grasslands and indicate that the vegetation and ecosystem services of degraded grasslands are improved after appropriate fencing

Litter accumulation alters the abiotic environment and drives community successional changes in two fenced grasslands in Inner Mongolia

Fencing is an effective and practical method for restoring degraded grasslands in northern China. However, little is known about the role of excess litter accumulation due to long-term fencing in regulating abiotic environment and driving changes in community structure and function. We conducted a three-year field experiment in two fenced grasslands in Inner Mongolia, and monitored light quantity, soil temperature, and soil moisture continuously, and determined community height, community aboveground net primary productivity (ANPP), and the relative dominance of different plant functional groups. Litter accumulation reduced light quantity and soil temperature but increased soil moisture. The regulating effects of litter accumulation on soil temperature and soil moisture fluctuated temporally and gradually weakened over the growing season. Litter accumulation also altered community vertical structure and function by increasing community height and ANPP. The increase in soil moisture increased the relative dominance of rhizome grasses but suppressed bunch grasses, thereby shifting bunch grass grasslands to rhizome grass grasslands. Our findings provide a potential mechanism for community succession in the context of litter accumulation in fenced grasslands and indicate that the vegetation and ecosystem services of degraded grasslands are improved after appropriate fencing

Vegetation classification at the association level under the China Vegetation Classification System: an example of six Stipa steppe formations in China

Aims The latest China Vegetation Classification System (China-VCS) for natural/semi-natural vegetation has eight hierarchical levels: Association < Association-group < Subformation < Formation < Formation-group < Vegetation-subtype < Vegetation-type < Vegetation-type-group. The classification is based on dominant species and their growth forms and has been completed at the formation level. The principal challenge today in Chinese vegetation classification is to develop the China-VCS at levels below the formation in a way that is consistent with current international standards. We explored the following question: how can existing vegetation plot data help develop the China-VCS and improve its compatibility with other international classification systems? Methods We compiled 401 plots having plant cover and/or aboveground biomass measurements collected in six Stipa steppe formations and divided them into those with cover data (299 plots) and/or biomass data (283 plots). We applied a combination of hierarchical clustering and ordination to partition the cover and biomass data sets into formations and constituent associations. We then used supervised noise clustering to improve the classification and to identify the core plots representing each association. Diagnostic species were also identified at both association and formation levels. Finally, we compared the classification results based on cover and biomass data sets and combined these results into a comprehensive classification framework for the six formations. Important Findings Our results using cover data were comparable with those using biomass data at both formation and association levels. Three Stipa formations were classified into associations based on cover data, two based on biomass data and one based on both biomass and cover data. Twenty-seven associations were defined and proposed within the six formations, using cover or biomass data as consistent classification sections (CCSs). Both dominant species in the dominant stratum and diagnostic species from multiple strata of the core plots were used to characterize vegetation types at both formation and association levels, improving the compatibility of our classification with the International Vegetation Classification. Temperature and precipitation were found to be important climatic factors determining the distribution pattern and species composition of Stipa-dominated vegetation. We propose a framework for plot-based vegetation classification in the China-VCS, using our work with Stipa-dominated steppe vegetation as an example. We applied the concept of CCS to make optimal use of available data representing both plant cover and biomass. This study offers a model for developing the China-VCS to the association level in a way that is consistent with current international standards

Assessing the collapse risk of Stipa bungeana grassland in China based on its distribution changes

The criteria used by International Union for Conservation of Nature (IUCN) for its Red List of Ecosystems (RLE) are the global standards for ecosystem-level risk assessment, and they have been increasingly used for biodiversity conservation. The changed distribution area of an ecosystem is one of the key criteria in such assessments. The Stipa bungeana grassland is one of the most widely distributed grasslands in the warm-temperate semi-arid regions of China. However, the total distribution area of this grassland was noted to have shrunk and become fragmented because of its conversion to cropland and grazing-induced degradation. Following the IUCN-RLE standards, here we analyzed changes in the geographical distribution of this degraded grassland, to evaluate its degradation and risk of collapse. Past (1950-1980) distribution areas were extracted from the Vegetation Map of China (1:1,000,000). Present realizable distribution areas were equated to these past areas minus any habitat area losses. We then predicted the grassland's present and future (under the Representative Concentration Pathway 8.5 scenario) potential distribution areas using maximum entropy algorithm (MaxEnt), based on field survey data and nine environmental layers. Our results showed that the S. bungeana grassland was mainly distributed in the Loess Plateau, Hexi Corridor, and low altitudes of the Qilian Mountains and Longshou Mountain. This ecosystem occurred mainly on loess soils, kastanozems, steppe aeolian soils and sierozems. Thermal and edaphic factors were the most important factors limiting the distribution of S. bungeana grassland across China. Since 56.1% of its past distribution area (4.9x10(4) km(2)) disappeared in the last 50 a, the present realizable distribution area only amounts to 2.2x10(4) km(2). But only 15.7% of its present potential distribution area (14.0x10(4) km(2)) is actually occupied by the S. bungeana grassland. The future potential distribution of S. bungeana grassland was predicted to shift towards northwest, and the total area of this ecosystem will shrink by 12.4% over the next 50 a under the most pessimistic climate change scenario. Accordingly, following the IUCN-RLE criteria, we deemed the S. bungeana grassland ecosystem in China to be endangered (EN). Revegetation projects and the establishment of protected areas are recommended as effective ways to avert this looming crisis. This empirical modeling study provides an example of how IUCN-RLE categories and criteria may be valuably used for ecosystem assessments in China and abroad

Sulfur and oxygen isotopes of sulfate extracted from Early Cambrian phosphorite nodules: Implications for marine redox evolution in the Yangtze Platform

© 2016, China University of Geosciences and Springer-Verlag Berlin Heidelberg. Phosphorite nodule beds are discovered in the black shale of basal Niutitang Formation throughout the Yangtze Platform in South China, recording an important phosphorite-generation event. Platform-wide phosphorite precipitation requires special oceanographic and geochemical conditions, thus the origin of the Niutitang phosphorite nodules may provide valuable information about the ocean chemistry in the Early Cambrian. In this study, we measured sulfur and oxygen isotopic compositions of sulfate extracted from phosphorite nodules collected from the basal Niutitang Formation. Phosphorite associated sulfate (PAS) is a trace amount of sulfate that incorporates into crystal lattice during phosphorite precipitation, accordingly PAS records the geochemical signals during phosphorite nodule formation. Sulfur isotopic composition of PAS (δ34SPAS) ranges from -1.16‰ to +24.48‰ (mean=+8.19‰, n=11), and oxygen isotopic value (δ18OPAS) varies between -5.3‰ and +26.3‰ (mean=+7.0‰, n=8). Most phosphorite nodules have low δ34SPAS and low δ18OPAS values, suggesting PAS mainly derived from anaerobic oxidation of H2S within suboxic sediment porewater. We propose that phosphate was delivered to the Yangtze Platform by a series of upwelling events, and was scavenged from seawater with the precipitation of FeOOH. The absorbed phosphate was released into suboxic porewater by the reduction of FeOOH at the oxic-suboxic redox boundary in sediments, and phosphorite nodule precipitated by the reaction of phosphate with Ca2+ diffused from the overlying seawater. The platform-wide deposition of phosphorite nodules in the basal Niutitang Formation implies the bottom water might be suboxic or even oxic, at least sporadically, in Early Cambrian. We speculate that the intensified ocean circulation as evident with frequent occurrences of upwelling events might be the primary reason for the episodic oxidation of the Yangtze Platform in Early Cambrian