潜在地震灾害预测和评价神经网络系统及其若干问题

结合人工神经网络自身的特性和地震灾害预测研究的特点,本文应用神经网络模型,建立了潜在地震灾害预测和评价系统。针对网络模型参数设置、数据归一化、中间层神经元最优数目以及泛化分类评价指标等若干实际问题给出了实际可行的解决方案。通过大样本数据对网络的训练,形成了有识别和记忆功能的非线性预测和评价系统。对网络的测试和检验,论证了该系统在预测潜在地震灾害上的可行性和有效性。同时,从测试精度出发,探讨了这种预测网络存在的不足,并给出了相应的改进建议,为开展进一步的研究工作提供了参考。     

The conservation patterns of grassland ecosystem in response to the forage-livestock balance in North China

Being a key ecological security barrier and production base for grassland animal husbandry in China,the balance between grassland forage supply and livestock-carrying pressure in North China directly affects grassland degradation and restoration,thereby impacting grassland ecosystem services.This paper analyzes the spatiotemporal variation in grassland vegetation coverage,forage supply,and the balance between grassland forage supply and livestock-carrying pressure from 2000 to 2015 in North China.We then discuss the spatial pattern of grassland ecological conservation under the impacts of grassland degradation and restoration,and livestock-carrying pressure.Over the last 16 years,the total grassland area in North China decreased by about 16,000 km2,with vegetation coverage degraded by 6.7％ of the grasslands but significantly restored by another 5.4％ of grasslands.The provisioning of forage by natural grassland mainly increased over time,with an annual growth rate of approximately 0.3 kg/ha,but livestock-carrying pressure also increased continuously.The livestock-carrying pressure index without any supplementary feeding reached as high as 3.8.Apart from the potential livestock-carrying capacity in northeastern Inner Mongolia and the central Tibetan Plateau,most regions in North China are currently overloaded.Considering the actual supplementary feeding during the cold season,the livestock-carrying pressure index is about 3.1,with the livestock-carrying pressure mitigated in central and eastern Inner Mongolia.Assuming full supplementary feeding in the cold season,livestock-carrying pressure index will fall to 1.9,with the livestock-carrying pressure alleviated significantly in Inner Mongolia and on the Tibetan Plateau.Finally,we propose different conservation and development strategies to balance grassland ecological conservation and animal husbandry production in different regions of protected areas,pastoral areas,farming-pastoral ecotone,and farming areas,according to the grassland ecological protection patterns.     

Spatial variation and driving mechanism of soil organic carbon components in the alluvial/sedimentary zone of the Yellow River

Alluviation and sedimentation of the Yellow River are important factors influencing the surface soil structure and organic carbon content in its lower reaches. Selecting Kaifeng and Zhoukou as typical cases of the Yellow River flooding area, the field survey, soil sample collection, laboratory experiment and Geographic Information System(GIS) spatial analysis methods were applied to study the spatial distribution characteristics and change mechanism of organic carbon components at different soil depths. The results revealed that the soil total organic carbon(TOC), active organic carbon(AOC) and nonactive organic carbon(NOC) contents ranged from 0.05–30.03 g/kg, 0.01–8.86 g/kg and 0.02–23.36 g/kg, respectively. The TOC, AOC and NOC contents in the surface soil layer were obviously higher than those in the lower soil layer, and the sequence of the content and change range within a single layer was TOCNOCAOC. Geostatistical analysis indicated that the TOC, AOC and NOC contents were commonly influenced by structural and random factors, and the influence magnitudes of these two factors were similar. The overall spatial trends of TOC, AOC and NOC remained relatively consistent from the 0–20 cm layer to the 20–100 cm layer, and the transition between high-and low-value areas was obvious, while the spatial variance was high. The AOC and NOC contents and spatial distribution better reflected TOC spatial variation and carbon accumulation areas. The distribution and depth of the sediment, agricultural land-use type, cropping system, fertilization method, tillage process and cultivation history were the main factors impacting the spatial variation in the soil organic carbon(SOC) components. Therefore, increasing the organic matter content, straw return, applying organic manure, adding exogenous particulate matter and conservation tillage are effective measures to improve the soil quality and attain sustainable agricultural development in the alluvial/sedimentary zone of the Yellow River.     

A coupled discrete element model for the simulation of soil and water flow through an orifice

Soil erosion around defective underground pipes can cause ground collapses and sinkholes in urban areas. Most of these soil erosion events are caused by fluidization of the surrounding soil with subsequent washing into defective sewer pipes. In this study, this soil erosion process is simplified as the gradual washout of sand particles mixed with water through an orifice. The discrete element method is used to simulate the large deformation behavior of the sand particles, and the Darcy fluid model is coupled with this approach to simulate fluid flow through porous sand media. A coupled 3D discrete element model is developed and implemented based on this scheme. To simulate previous experiments using this coupled model considering the current computing capacity, we incorporated a ‘supply layer’ to study the continuous erosion process. The coupled model can predict the erosion flow rates of sand and water and the shape of erosion void. Thus, the model can be used as an effective and efficient tool to investigate the soil erosion process around defective pipes. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluating the spatiotemporal variations of water budget across China over 1951–2006 using IBIS model

The Integrated Biosphere Simulator is used to evaluate the spatial and temporal patterns of the crucial hydrological variables [run‐off and actual evapotranspiration (AET)] of the water balance across China for the period 1951–2006 including a precipitation analysis. Results suggest three major findings. First, simulated run‐off captured 85% of the spatial variability and 80% of the temporal variability for 85 hydrological gauges across China. The mean relative errors were within 20% for 66% of the studied stations and within 30% for 86% of the stations. The Nash–Sutcliffe coefficients indicated that the quantity pattern of run‐off was also captured acceptably except for some watersheds in southwestern and northwestern China. The possible reasons for underestimation of run‐off in the Tibetan plateau include underestimation of precipitation and uncertainties in other meteorological data due to complex topography, and simplified representations of the soil depth attribute and snow processes in the model. Second, simulated AET matched reasonably with estimated values calculated as the residual of precipitation and run‐off for watersheds controlled by the hydrological gauges. Finally, trend analysis based on the Mann–Kendall method indicated that significant increasing and decreasing patterns in precipitation appeared in the northwest part of China and the Yellow River region, respectively. Significant increasing and decreasing trends in AET were detected in the Southwest region and the Yangtze River region, respectively. In addition, the Southwest region, northern China (including the Heilongjiang, Liaohe, and Haihe Basins), and the Yellow River Basin showed significant decreasing trends in run‐off, and the Zhemin hydrological region showed a significant increasing trend. Copyright © 2009 John Wiley & Sons, Ltd.     

Long‐term effects of revegetation on soil hydrological processes in vegetation‐stabilized desert ecosystems

Planting of sand‐binding vegetation in the Shapotou region on the southeastern edge of the Tengger Desert began in 1956. The revegetation programme successfully stabilized formerly mobile dunes in northern China, permitting the operation of the Baotou‐Lanzhou railway. Long‐term monitoring has shown that the revegetation programme produced various ecological changes, including the formation of biological soil crusts (BSCs). To gain insight into the role of BSCs in both past ecological change and current ecological evolution at the revegetation sites, we used field measurements and HYDRUS‐1D model simulations to investigate the effects of BSCs on soil hydrological processes at revegetated sites planted in 1956 and 1964 and at an unplanted mobile dune site. The results demonstrate that the formation of BSCs has altered patterns of soil water storage, increasing the moisture content near the surface (0–5 cm) while decreasing the moisture content in deeper layers (5–120 cm). Soil evaporation at BSC sites is elevated relative to unplanted sites during periods when canopy coverage is low. Rainfall infiltration was not affected by BSCs during the very dry period that was studied (30 April to 30 September 2005); during periods with higher rainfall intensity, differences in infiltration may be expected due to runoff at BSC sites. The simulated changes in soil moisture storage and hydrological processes are consistent with ongoing plant community succession at the revegetated sites, from deep‐rooted shrubs to more shallow‐rooted herbaceous species. Copyright © 2009 John Wiley & Sons, Ltd.     

Behaviors of trace elements and relationships between the compositions of solid phase and melt during fractional crystallization

Given r_i =f _i(F) andK _i = g_i(F), wherer _i is the mineral mass fraction in an instantaneous solid phase,K _i the partition coefficient, andf _i(F) andg _i(F) respectively the continuous, sectionally smooth functions of solidification degreeF, we have: $$C^1 = \frac{{C_0 }}{{1 - F}} \cdot \exp \left( { - \int_0^F {\frac{{\Sigma fi(F) \cdot g_i (F)}}{{1 - F}} \cdot dF} } \right)and \bar C^s = \frac{{C_o }}{F}\left[ {1 - (1 - F) \cdot \frac{{C^1 }}{{C^0 }}} \right]$$ Also presented in this paper are other equations describing the compositional changes of solid and liquid phases in magmatic processes (partial melting). The following understanding is attained based on the application of these equations to the Hushan pluton of Mt. Taishan in the west of Shandong Province. 1) For granitoids changes in rock-forming minerals may not be taken into consideration in theoretical modelling of REE distribution, but accessory minerals rich in REE, especially those highly rich in some REE must be taken into account. 2) In the case of well differentiated granitoids, it can be assumed thatFε [0,1] may exert only little influence on the calculations. 3) In practice the (La / Sm)-La diagram should be applied with care.     

Sensitivity experiments on summer monsoon circulation cell in east asia

The East-Asian summer monsoon meridional circulation (SMMC) cell is simulated together with two vigorous rainbands in terms of a primitive-equation model including in itself a variety of diabatic heating, frictional dissipation and moist processes under the condition of mountains available. Results are comparable to observations. Also, performed are experiments with the reduction of water content, and exclusion of the cumulus convective process and mountain effect. Contrast analyses indicate that the cell is strongly sensitive to the condition of the humidity field in the atmosphere, more intensely at 120o than at 100oE, and the presence (absence) of the cumulus convection has considerable effect on the intensification (weakening) of the cell, with the mountain ranges exhibiting more influence upon the cell at 100o than 120oE. This may suggest that a great difference lies in the cause of the cell for the two meridions.     

西藏羊八井地热田水热蚀变

本文对羊八井地热田钻扎ZK-201、ZK-301和ZK-308的岩心进行了较系统的蚀变矿物学、岩石学和流体包体研究。划分出6个蚀变矿物共生组合及蚀变分带,讨论了蚀变过程中岩石化学变化的特点,并推测了蚀变的温度和酸碱度条件。研究表明,热田曾处于极度的活动状态,最高温度达220-240℃,由于冷水的入侵,热田在目前钻探所及范围已冷却了50-70℃。蚀变矿物分布模式表明,目前热田流体主通道位于北部,热田进一步的开发应以寻找北部深部高温流体为主。