Permeability tensor and representative elementary volume of fractured rock masses

Based on a simulation of three-dimensional fracture networks and a superposition principle of liquid dissipation energy for fractured rock masses, a model of the fracture permeability tensor is proposed. An elastic constitutive model of rock fractures, considering fracture closure and dilation during shearing, is also proposed, based on the dilation angle of the fracture. Algorithms of flow-path searching and calculation of the effective flow coefficients for fracture networks are presented, together with a discussion on the influence of geometric parameters of the fractures (trace length, spacing, aperture, orientation and the number of fracture sets) on magnitude, anisotropy of hydraulic permeability and the size of a representative elementary volume (REV). The anisotropy of hydraulic permeability of fractured rock masses is mainly affected by orientation and the number of fracture sets, and the REV size is mainly influenced by trace length, spacing and the number of fracture sets. The results of studies on REV size and the influence of in-situ stress on hydraulic conductivity of the rock mass on the slope of Jinping-I hydropower station, China, are presented using the developed models and methods. The simulation results agreed well with the results obtained from field water-pressure measurements, with an error of less than 10 %.     

Application of capacitive deionization technology to the removal of sodium chloride from aqueous solutions

Capacitive deionization has been developed as a promising desalination alternative for removing ions from aqueous solutions. In this study, the evaluation of capacitive performance was carried out by galvanostatic charge/discharge and cyclic voltammetry experiments. The good capacitive and electrosorption behaviors suggest carbon aerogel not only treated as an electrical double layer capacitor, but also as a potential electrode in capacitive deionization processes. Also, the capacitive deionization characteristics indicate that electrosorption/regeneration can be controlled by polarization and depolarization of each electrode. It implies that sodium and chloride ions are electrostatically held to form electrical double layer on the surface of charged electrodes. The electrosorption performance at different applied voltages and solution concentrations was investigated. It is found that the removal of sodium chloride increases with increasing applied voltage and solution concentration, resulting from stronger electrostatic interactions, higher concentration gradient, and less double layer overlapping effect. Based on Langmuir isotherm, the equilibrium electrosorption capacity at 1.2 V is determined as 270.59 μmol/g. Under this condition, due to the presence of micropores associated with the double layer overlapping, the effective surface area for electrosorption of ions at 1.2 V is estimated in the range of 12.18–14.25 % of the Brunauer–Emmett–Teller surface area. The results provide a fundamental understanding of electrosorption of ions and help promoting capacitive deionization technology for water purification and desalination.     

The relationship of vegetation and soil differentiation during the formation of black-soil-type degraded meadows in the headwater of the Qinghai-Tibetan Plateau, China

In alpine meadow ecosystems, considerable spatial heterogeneity in forb-dominant vegetation exists as a result of severe grassland degeneration; however, there is limited quantitative information on the vegetative differences between degenerated and pristine grasslands. Therefore, a field study, which seeks to identify the edaphic factors driving the variation in plant composition and distribution, was conducted in a severely degraded alpine meadow located in the Qinghai-Tibetan Plateau, NW China. Five meadows, an original meadow and four degraded meadows, were used to determine the differentiation and relationships between the vegetation and soil of degraded alpine meadows. The dominated species of these degraded meadows are Ligularia virgaurea–Artemisia gmelinii (LA), Oxytropis ochrocephala–Leontopodium nanum (OL), Aconitum pendulum–Potentilla anserina (AP) and Stellera chamaejasme–Artemisia nanschanica (SA), respectively. The results indicate that vegetation cover, grass biomass, species number and diversity indices clearly decrease from the original to the degraded meadow. Soil water, clay and nutrient content are also reduced with grassland degradation in surface and subsoil layers. The joint study of floristic and edaphic variables confirms that the soil features, especially the bulk density, sand content, pH, salinity, N and K, mainly determine the establishment of vegetation in the severely degraded fields of this study. These results may be useful for alpine grassland ecosystem restoration and management.     

Free Return Trajectories in Lunar Missions

Four types of symmetric free return trajectories in the planar circular restricted three-body problem are computed and compared with each other. One of these four types is most applicable in practice. Concentrating ourselves on this special type of free return trajectory, the corresponding planar asymmetric cases are studied. Then the studies are generalized to the three-dimensional case. The restrictions on the inclination angle of the probe at the perilune are discussed. It is found that the maximum inclination at the perilune between the probe's orbit plane and the Moon's orbit plane is restricted by the heights of the perigee and the perilune of the free return trajectory. However, the inclination at the perigee is nearly not affected by them. At last, a strategy to design free return trajectories in the real Earth-Moon system is proposed. Some numerical simulations are done to show the feasibility of this orbit design strategy. The discussions from the planar case to the spatial case and then to the real force model can also be applied to the other three types of planar free return trajectories.     

Enhancing the culturability of bacteria from the gastrointestinal tract of farmed adult turbot Scophthalmus maximus

Eighteen agar media were tested for the culture of gut-associated bacteria from farmed adult turbot(Scophthalmus maximus),including 16 agar media with or without 1% gastrointestinal(GI)supernatant,or with 2% or 4% GI supernatant.A total of 1 711 colonies were analyzed and 24 operational taxonomic units(OTUs)were identifi ed.The greatest bacterial diversity was isolated on Zobell 2216E/Zobell 2216E+ agar media,whereas MRS/MRS+ agar media produced a low diversity of colonies.Agar media with GI supernatant(1%,2%,or 4%)showed increased diversity and yielded different profi les of OTUs from the corresponding original media,suggesting that GI supernatant provides substances that enhance the culture effi ciency of bacteria from the turbot GI tract.The large majority of the colonies(82%)were γ-Proteobacteria,whereas 15.6% and 2.4% of colonies were Firmicutes and Actinobacteria,respectively.At the genus level,49.4% of all colonies were assigned to Vibrio.Other potential pathogens,including Pseudomonas,Photobacterium,and Enterobacter,and potential probiotics,including Bacillus,Paenibacillus,and Pseudomonas,were also isolated on agar media.Most cultured bacteria belonged to species that were fi rst described in the turbot GI tract.The impact of these species on turbot physiology and health should be investigated further.     

The benefits of recent warming for maize production in high latitude China

Latitudes above 45°N have been characterized by rates of warming faster than the global average since 1980. However, the effects of this warming on crop production at these latitudes are still unclear. Using 30-years of weather and crop management data in Heilongjiang area of China (43.4° to 53.4°N), combined with the Hybrid-Maize model, we show that that maize yields would have stagnated in most areas and decreased in the southern part of Heilongjiang if varieties were assumed fixed since 1980. However, we show that through farmers’ adaptation, warming has benefitted maize production for much of this region. Specifically, farmers gradually chose longer maturing varieties, resulting in a net 7–17 % yield increase per decade. Meanwhile, farmers also rapidly expanded maize area (from 1.88 million ha in 1980 to 4.01 million ha in 2009) and the northward limit of maize area shifted by more than 290 km from ~50.8°N to ~53.4°N. Overall, benefits from warming represented 35 % of the overall yield gains in the region over this period. The results indicate substantial ongoing adaptations and benefits at north high-latitudes, although they still represent a small fraction of global maize area. The sustainability of crop area expansion in these regions remains unclear and deserves further study.     

浅谈信号干扰对区域自动气象站的数据传输影响

区域自动气象站在气象监测和防灾减灾的作用日益突出,随着大量区域自动气象站的建成并投入使用,后续的维护及故障排除等成为热点问题.对区域自动气象站几例信号干扰的故障处理进行分析,找出故障的原因,并提出相应的解决办法,为区域自动气象站的稳定运行、及时维护、高效管理提供参考.     

Topographic controls on alpine treeline patterns on Changbai Mountain,China

The control mechanisms of topography on alpine treeline pattern are critical to understanding treeline dynamics and future changes. These mechanisms have not been understood quite well enough because of increasing human disturbance and low data resolution. In this study, the relationship between the treeline pattern and topography was analyzed based on high spatial resolution remote sensing data and a digital elevation model in an area in Changbai Mountain with little human disturbance. Future treeline patterns were also predicted. The results showed that(a) aspects with high solar radiation and low snow cover have a high coverage rate of trees,(b) the peak coverage rate of trees switches from low slopes(5°) to medium slopes(5°~25°) as the elevation rises because of the extreme environment,(c) the coverage rate of trees is a function that depends on environmental factors controlled by topography,(d) the future treeline pattern is controlled by new temperature mechanisms, new environmental factors and the reallocation effect of topography. Our research implies that topography controls the treeline pattern and changes in the treeline pattern associated with global warming, due to the effect of global warming on environmental factors. This study may well explain the causes of heterogeneous changes in the treeline pattern in the horizontal direction as well as differences in treeline response to climate warming.     

Remote sensing survey and research on internal solitary waves in the South China Sea-Western Pacific-East Indian Ocean (SCS-WPAC-EIND)

Internal solitary waves (ISWs) are common mesoscale dynamic processes in the ocean that are spread throughout the world’s oceans. The South China Sea (SCS), Western Pacific (WPAC) and Indian Ocean (EIND) (SCS-WPAC-EIND) are areas where ISWs frequently occur. In particular, in the northern part of the South China Sea, Sulu Sea, Celebes Sea, Andaman Sea, Lombok Strait and northeastern part of Taiwan Island, ISWs exist almost year-round. Remote sensing is an important technique to carry out investigations and research on ISWs on a large scale. In particular, optical sensors represented by the Moderate Resolution Imaging Spectroradiometer (MODIS) can observe ISWs for a long time and on a large scale, while SAR sensors such as Sentinel-1 A/B can compensate for the deficiencies in optical sensors and comprehensively observe ISWs. Based on many years of remote sensing surveys of ISWs, this paper uses MODIS and Sentinel-1 satellite remote sensing images of more than 70 000 scenes from 2010 to 2020 to carry out survey studies of ISWs in the SCS-WPAC-EIND. The survey systematically gives the temporal and spatial distribution characteristics of ISWs in the SCS-WPAC-EIND and focuses on the analysis of the ISW characteristics in main areas in the SCS-WPAC-EIND, thereby providing basic data for further research on ISWs.     

Experimental Study on Scouring and Silting Deformation of Artificial Beach Under Storm Surge-Wave Coupling

With the increasing construction of artificial beach in coastal areas, it is of practical significance to study the beach surface deformation of artificial beach profile. Previous studies only focus on a single wave dynamic factor, and it is difficult to predict the beach deformation of artificial beach profile under the storm surge-wave co-action. To solve this problem, the cross-section physical model test method was used to study the beach surface deformation of a typical artificial beach pro...