198 research outputs found
THE SERVICE MODELS AND TECHNICAL MODELS OF AGRICULTURAL INFORMATIONIZATION
Types of rural-urban gaps exist and seem expand in China, although agriculture and rural lives have obtained significant enhancement since the opening and reforming policy started in 1980. Amongst these gaps, digital gap is critical itself, and may widen other gaps. How to promote agricultural infor-mationization (agri-informationization) effectively and efficiently is a great challenge to Chinese government and Chinese people nowadays. Meanwhile, the agri-informationization also brings opportunities with new markets, new technology and new rural culture, etc. Firstly, this article introduces the background about Chinese rural areas and rural economy in brief. Secondly, it gives focus on typical types of information service models and information technical models which appearing in the process of agri-informationization. Thirdly, the problems and challenges are analyzed. Finally, the article ends up with a conclusion section. We wish the information service models and technical models introduced here be meaningful references for multiple stakeholders, such as police-makers, basic-level officers, farmers, and information companies, in China and in other developing countries
Transport Model of Underground Sediment in Soils
Studies about sediment erosion were mainly concentrated on the river channel sediment, the terrestrial sediment, and the underground sediment. The transport process of underground sediment is studied in the paper. The concept of the flush potential sediment is founded. The transport equation with stable saturated seepage is set up, and the relations between the flush potential sediment and water sediment are discussed. Flushing of underground sediment begins with small particles, and large particles will be taken away later. The pore ratio of the soil increases gradually. The flow ultimately becomes direct water seepage, and the sediment concentration at the same position in the water decreases over time. The concentration of maximal flushing potential sediment decreases along the path. The underground sediment flushing model reflects the flushing mechanism of underground sediment
Genuine Dirac half-metal: A 2D d0-type ferromagnet Mg4N4
When the spin-orbit coupling (SOC) is absent, almost all the proposed
half-metals with the twofold degenerate nodal points at the K (or K') in
two-dimensional (2D) materials are misclassified as "Dirac half-metals" owing
to the way graphene was utilized in the earliest studies. Actually, each band
crossing point at K or K' is described by a 2D Weyl Hamiltonian with definite
chirality; hence, it must be a Weyl point. To the best of our knowledge, there
have been no reports of a genuine (i.e., fourfold degenerate) Dirac point
half-metal in 2D yet. In this Letter, we proposed for the first time that the
2D d0-type ferromagnet Mg4N4 is a genuine Dirac half-metal with a fourfold
degenerate Dirac point at the S high-symmetry point, intrinsic magnetism, high
Curie temperature, 100% spin-polarization, robustness to the SOC and uniaxial
and biaxial strains, and 100% spin-polarized edge states. The work can be seen
as a starting point for future predictions of intrinsically magnetic materials
with genuine Dirac points, which will aid the frontier of topo-spintronics
researchers
Recipe for single-pair-Weyl-points phonons carrying the same chiral charges
Recently, Wang et al. [Phys. Rev. B, 106, 195129 (2022)] challenged a widely
held belief in the field of Weyl physics, demonstrating that
single-pair-Weyl-points (SP-WPs) can exist in nonmagnetic spinless systems,
contrary to previous assumptions that they could only exist in magnetic
systems. Wang et al. observed that the SP-WPs with opposite and even chiral
charges (i.e., |C| = 2 or 4) could also exist in nonmagnetic spinless systems.
In this Letter, we present a novel finding in which SP-WPs have a partner,
namely a charged nodal surface, in nonmagnetic spinless systems. In contrast to
previous observations, we show that the SP-WPs can have uneven chiral charges
(i.e., |C| = 1). We identify 6 (out of 230) space groups (SGs) that contain
such SP-WPs by searching the encyclopedia of emergent particles in
three-dimensional crystals. Our finds were confirmed through the phonon spectra
of two specific materials Zr3O (with SG 182) and NaPH2NO3 (with SG 173). This
discovery broadens the range of materials that can host SP-WPs and applies to
other nonmagnetic spinless crystals
CrX (X=Se, Te) monolayers as new platform to realize robust spin filter, spin diode and spin valve
Two-dimensional ferromagnetic (FM) half-metals are promising candidates for
advanced spintronic devices with small-size and high-capacity. Motivated by
recent report on controlling synthesis of FM CrTe nanosheet, herein, to
explore the potential application in spintronics, we designed spintronic
devices based on CrX (X=Se, Te) monolayers and investigated their spin
transport properties. We found that CrTe monolayer based device shows
spin filtering and dual spin diode effect when applying bias voltage, while
CrS monolayer is an excellent platform to realize a spin valve. The
different transport properties are primarily ascribed to the semiconducting
spin channel, which is close to and away from the Fermi level in CrTe
and CrSe monolayers, respectively. Interestingly, the current in
monolayer CrSe based device also displays a negative differential
resistance effect (NDRE) and a high magnetoresistance ratio (up to 2*10).
Moreover, we found thermally induced spin filtering effect and NDRE in
CrSe junction when applying temperature gradient instead of bias
voltage. These theoretical findings highlight the potential of CrX
(X=Se, Te) monolayers in spintronic applications and put forward realistic
materials to realize nanosale spintronic device
Solving the mystery of vanishing rivers in China
A major controversy was sparked worldwide by a recent national water census claiming that the number of Chinese rivers with watersheds ≥100 km2 was less than half the previous estimate of 50 000 rivers, which also stimulates debates on the potential causes and consequences. Here, we estimated the number of rivers in terms of stream-segmentation characteristics described by Horton, Strahler and Shreve stream-order rules, as well as their mixed mode for named rivers recorded in the Encyclopedia of Rivers and Lakes in China. As a result, the number of 'vanishing rivers' has been found to be highly relevant to statistical specifications in addition to the erroneous inclusion of pseudo-rivers primarily generated in arid or frost-thaw areas. The modified Horton stream-order scheme reasonably depicts the configuration of complete natural streams from headwater to destination, while the Strahler largely projects the fragmentation of the named river networks associated with human aggregation to the hierarchical river systems
A novel termini analysis theory using HTS data alone for the identification of Enterococcus phage EF4-like genome termini
Universal relation with regime transition for sediment transport in fine-grained rivers
Fine-grained sediment (grain size under 2,000 μm) builds floodplains and deltas, and shapes the coastlines where much of humanity lives. However, a universal, physically based predictor of sediment flux for fine-grained rivers remains to be developed. Herein, a comprehensive sediment load database for fine-grained channels, ranging from small experimental flumes to megarivers, is used to find a predictive algorithm. Two distinct transport regimes emerge, separated by a discontinuous transition for median bed grain size within the very fine sand range (81 to 154 μm), whereby sediment flux decreases by up to 100-fold for coarser sand-bedded rivers compared to river with silt and very fine sand beds. Evidence suggests that the discontinuous change in sediment load originates from a transition of transport mode between mixed suspended bed load transport and suspension-dominated transport. Events that alter bed sediment size near the transition may significantly affect fluviocoastal morphology by drastically changing sediment flux, as shown by data from the Yellow River, China, which, over time, transitioned back and forth 3 times between states of high and low transport efficiency in response to anthropic activities
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