荒漠绿洲湿地土壤水热盐动态过程及其影响机制

以甘肃临泽荒漠绿洲湿地为研究对象,通过对土壤温度、含水量、电导率及蒸散量的野外观测,在植物生长期和冻融期分别深入分析水热盐耦合运移过程及其影响因素,探讨水热梯度对盐分运移及其分布格局的控制作用。结果表明：土壤温度整体呈现出春夏季逐渐升高、秋冬季降低趋势。在冻结期,土壤表现为脱盐状态,表层电导率由2.8 mS·cm^-1降到1.2 mS·cm^-1;而在消融期为积盐状态,表层电导率由1.2 mS·cm^-1升到3.7 mS·cm^-1。在生长期,土壤含水量和电导率波动较为剧烈,表层含水量27%~43%,表层电导率3~5.5 mS·cm^-1,土壤脱盐、积盐反复出现。全年蒸散量总体呈单峰变化趋势,年蒸散量507 mm;土壤电导率与蒸散量呈正比关系,与地下水位呈负相关关系;蒸散发作用是土壤表层积盐的主要驱动力,而地下水波动影响着湿地脱盐、洗盐过程。因此,荒漠绿洲湿地土壤盐分累积过程是水分运移和热量传输过程发生变化的结果。     

基于无人机和MODIS数据的巴丹吉林沙漠植被分布特征与动态变化研究

荒漠植被在减缓沙漠扩张、阻挡风沙入侵绿洲、维护绿洲稳定性方面具有重要意义。通过无人机搭载多光谱相机获取地面样地高分辨率NDVI数据以计算植被覆盖度,结合MODIS-NDVI数据,分析了MODIS-NDVI与无人机获取NDVI数据之间的一致性,进而建立MODIS-NDVI数据与样方植被覆盖度的空间反演模型,以研究巴丹吉林沙漠植被分布特征、动态变化及其对气温、降水的响应规律。结果表明:(1)基于无人机多光谱数据大样方植被覆盖度和MODIS-NDVI数据构建的植被覆盖度反演模型具有较高的模拟精度。(2)研究区总体植被覆盖度较低,空间上呈由东南向西北递减的趋势。(3)植被覆盖度总体呈现上升趋势,沙漠边缘的增速较沙漠内部更为明显,其中沙漠边缘增长率达1.53%/10a,而沙漠内部为0.84%/10a。沙漠边缘57.12%植被出现改善,而沙漠内部植被改善的面积约为21.26%。(4)植被生长主要受制于生长季降水量并呈现出明显的季节变化,此外植被对降水和气温的响应存在一定的滞后效应。     

OGC CSW规范实现探讨

OGC CSW规范的实现,主要包括元数据信息模型建立、属性项映射、结果编码格式定义和软件实现,实现过程中需要注意参数格式标准化、参数约束条件、参数变化、元数据信息模型、名称空间以及该规范的局限性。介绍OGC CSW规范与目录服务标准及相关规范的关系,回顾该规范实现情况,结合全国测绘成果目录服务系统研发建立的工作实践,对OGC CSW规范的实现步骤和需要注意的问题进行讨论,并以全国测绘成果目录服务系统为例,介绍OGC CSW规范的应用效果。     

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.     

钨、锡流-熔分配实验结果及其矿床成因意义

本文用实验确定了钨、锡在成分不同的花岗质熔体相与共存水热流体相的流-熔分配系数(D_(Me)~(V/L))及其与介质溶液(NaF,KF,HF,NaCl等水溶液)摩尔浓度间的函数关系。实验结果表明,钨、锡的分配行为明显不同。在相同条件下,随体系的不同,D_W~(V/L)比D_(Sn)~(V/L)大几倍至二十倍。钠和钾对钨、锡的流-熔分配行为的影响基本相同,而氟和氯对钨、锡的分配行为的影响相差甚远,花岗质熔体的主成分对D_W~(V/L)和D_(Sn)~(V/L)有复杂的影响。利用这些结果探讨与花岗岩有关的钨、锡矿床的成矿机理,得出了一些与前人不同的新认识。     

时序分析在危岩体监测数据处理中的应用

引入时间序列分析进行危岩体监测数据的处理，建立了危岩体变形的动态模型，取得了较好的拟会与预报精度。     

Measurements of level-crossing statistics of concentration fluctuations in plumes dispersing in the atmospheric surface layer

The statistics of level crossings and local extremes in concentration fluctuations in plumes dispersing in the atmosphere have been investigated. A set of concentration fluctuation tracer experiments has been utilized to measure the statistical propertics of the upcrossing interval (inter-arrival time between consecutive concentration bursts), excursion duration (persistence or width of concentration bursts), and concentration amplitude (difference between the maximum and minimum concentrations between successive upcrossings) with respect to a range of concentration crossing levels. In particular, the effect of downwind distance and atmospheric stratification on the level-crossing statistics has been studied in detail. It is shown that the effect of increasing atmospheric stability on level-crossing statistics is similar to the effect of increasing distance from the source in the sense that level-crossing statistics of concentration fluctuations in stable stratification resemble those in neutral stratification, but at a greater downwind distance. It is also found that the distribution of the interval between consecutive upcrossings of a concentration level, as well as the duration of an excursion across a concentration level, can be approximated by a lognormal distribution, whereas the distribution of the concentration amplitude is best characterized by a gamma distribution. Some implications of these results for the modeling of level-crossing statistics of concentration fluctuations are discussed.     

The difference in chemical composition of the 1962 lava from miyakezima magma reservoir in Japan

Many examples of mixed magmas in banded lavas have been studied. Another type of mixed magmas or inhomogeneity of magma reservoir found in the 1962 lava flows of Miyake-zima Volcano erupted from fissures is reported.     

Pneumatic beneficiation of coal fines using the counter-current fluidized cascade

The counter-current gas-fluidized cascade (CFC) is a novel pneumatic device for separating mixed granular solids according to specific gravity. The possible utility of the CFC for beneficiation of coal in all size-ranges is presently under investigation, and in this paper some results are reported on pyrite beneficiation of synthetic pyrite-coal mixtures, and also on pyrite and ash beneficiation of as-received coal. The (geometric) mean particle size, by weight, of the coal used with added pyrite was 153 μm, and of the natural coal 233 μm. Preliminary results on the concentration of pyrite and ash in the reject streams indicate that CFC has some potential of being a simple and low-cost device for coal beneficiation.