Nozzle optimization for water jet propulsion with a positive displacement pump

In the water jet propulsion system with a positive displacement （PD） pump, the nozzle, which converts pressure energy into kinetic energy, is one of the key parts exerting great influence on the reactive thrust and the efficiency of the system due to its high working pressure and easily occurring cavitation characteristics. Based on the previous studies of the energy loss and the pressure distribution of different nozzles, a model of water jet reactive thrust, which fully takes the energy loss and the nozzle parameters into consideration, is developed to optimize the nozzle design. Experiments and simulations are carried out to investigate the reactive thrust and the conversion efficiency of cylindrical nozzles, conical nozzles and optimized nozzles. The results show that the optimized nozzles have the largest reactive thrust and the highest energy conversion efficiency under the same inlet conditions. The related methods and conclusions are extended to the study of other applications of the water jet, such as water jet cutting, water mist fire suppression, water injection molding.     

Spatiotemporal characteristics,patterns, and caus-es of land-use changes in China since the late 1980s

Land-use/land-cover changes (LUCCs) have links to both human and nature interactions. China's Land-Use/cover Datasets (CLUDs) were updated regularly at 5-year intervals from the late 1980s to 2010,with standard procedures based on Landsat TM\ETM+ images. A land-use dynamic regionalization method was proposed to analyze major land-use conversions. The spatiotemporal characteristics,differences,and causes of land-use changes at a national scale were then examined. The main findings are summarized as follows. Land-use changes (LUCs) across China indicated a significant variation in spatial and temporal characteristics in the last 20 years (1990-2010). The area of cropland change decreased in the south and increased in the north,but the total area remained almost unchanged. The reclaimed cropland was shifted from the northeast to the northwest. The built-up lands expanded rapidly,were mainly distributed in the east,and gradually spread out to central and western China. Woodland decreased first,and then increased,but desert area was the opposite. Grassland continued decreasing. Different spatial patterns of LUC in China were found between the late 20th century and the early 21st century. The original 13 LUC zones were replaced by 15 units with changes of boundaries in some zones. The main spatial characteristics of these changes included (1) an accelerated expansion of built-up land in the Huang-Huai-Hai region,the southeastern coastal areas,the midstream area of the Yangtze River,and the Sichuan Basin;(2) shifted land reclamation in the north from northeast China and eastern Inner Mongolia to the oasis agricultural areas in northwest China;(3) continuous transformation from rain-fed farmlands in northeast China to paddy fields;and (4) effectiveness of the "Grain for Green" project in the southern agricultural-pastoral ecotones of Inner Mongolia,the Loess Plateau,and southwestern mountainous areas. In the last two decades,although climate change in the north affected the change in cropland,policy regulation and economic driving forces were still the primary causes of LUC across China. During the first decade of the 21st century,the anthropogenic factors that drove variations in land-use patterns have shifted the emphasis from one-way land development to both development and conservation.The "dynamic regionalization method" was used to analyze changes in the spatial patterns of zoning boundaries,the internal characteristics of zones,and the growth and decrease of units. The results revealed "the pattern of the change process," namely the process of LUC and regional differences in characteristics at different stages. The growth and decrease of zones during this dynamic LUC zoning,variations in unit boundaries,and the characteristics of change intensities between the former and latter decades were examined. The patterns of alternative transformation between the "pattern" and "process" of land use and the causes for changes in different types and different regions of land use were explored.     

南极拜尔斯半岛企鹅粪土沉积物元素地球化学特征

拜尔斯半岛位于南极利文斯顿岛最西部,是南设得兰群岛中最大的无冰区。对采自拜尔斯半岛的一根长55 cm的企鹅粪土沉积柱P1进行了元素和同位素地球化学分析。通过对沉积物C/N、有机质来源和δ15N的分析,发现P1沉积剖面中有机质主要来源于企鹅粪。利用富集系数、相关性分析、主成分分析等统计分析方法,识别出该沉积剖面中P、F、Cu、Hg、As、S六种元素具有共同的来源,与企鹅粪的输入密切相关,并且这些元素与TOC和δ15N显著正相关,说明沉积剖面中这些元素含量主要受控于企鹅粪的输入程度。通过与长城站区阿德雷岛、东南极戴维斯站加德纳岛企鹅粪土沉积物的标型元素特征比较,发现上述三个地区的标型元素组合大体上一致,反映了整个南极地区企鹅粪土沉积物生物标型元素组合的共性。研究结果为进一步恢复该地区的企鹅种群数量演化,及其对气候变化的响应提供了可能。     

北天山地区2011 年以来两次6 级地震前的地震学中短期异常特征

通过分析北天山地区历史强震、构造活动背景、区域应变能积累特征以及2011 年11月1 日尼勒克、巩留交界6. 0 级和2012 年6 月30 日新源、和静交界6. 6 级地震前区域地震活动异常特征等,探讨了这两次6 级地震前的地震学中短期异常特征。结果表明,2011 年6 月以来北天山地区中强以上地震处于加速活动状态,进入应变能释放阶段;尼勒克、巩留交界6. 0 级和新源、和静交界6. 6 级地震震前先呈6 级地震平静而后被打破、中强地震成组活动和空间迁移、条带和空区等较明显的中期异常;震前还出现了较为相似的4 级以上地震围空和5 级逼近地震,且逼近地震与主震发生时间间隔均为14 天,显示了较清晰的异常图像和较明显的中短期震兆特征。     

全球地球化学数据管理系统:“化学地球”软件研制

"数字地球"已经提出多年,是20世纪末期问世的定量化研究地球的一个新的战略方向。通过借鉴Google Earth,地质学界提出了建设One Geology和OGS-Earth多层次多学科应用平台的概念。进一步提出构建基于化学元素在地壳的分布可视化,建立"化学地球"或者叫做"元素地球"(命名为Chemical Earth),能直观地揭示地壳中元素的分布,反映出不同大地构造单元元素时空分布、演化历史和矿床的物质背景。本项研究主要完成两个方面的内容:(1)研发一个基于ArcGIS Server二维和三维统一的"化学地球"软件平台,类似于谷歌地球(Google Earth)的数字地球软件平台,实现对地球化学数据和图形适时进行二维(平面)和三维(球面)联动;(2)建立地球化学数据库和提供图形化工具,实现对数据库进行多种方式的查询统计,如对不同尺度地球化学图的显示、图形与数据交互查询和采样信息查询等。     

临清坳陷中二叠世古地理恢复

临清坳陷是一个中一新生代的断陷盆地,多期断层活动、多套生储盖组合、多种圈闭类型的地质条件,决定了临清坳陷可形成多类型的油气藏,具有良好的油气勘探前景。以临清坳陷中二叠世沉积地层为主要研究对象,观察钻井取心,详细分析测井标志,建立等时地层格架,基于等时地层格架进行古地理的恢复。研究表明,研究区共划分为2个层序,层序1为河控浅水三角洲环境,层序2过渡为内陆河流环境,对该区的勘探工作及勘探实践具有重要的理论和现实意义。     

Development of Rock Bolt Elements in Two-Dimensional Discontinuous Deformation Analysis

Computer modeling can be used to explore and gain new insights into the impacts of rock bolt intersecting joints in rock masses, and to estimate the effectiveness of the rock reinforcement system. In order to achieve this goal, we couple a rock bolt element into the two-dimensional discontinuous deformation analysis (DDA^2D) program. The coupling algorithm is based on the analytically-derived interface behavior between a rock bolt and the rock material for grouted rock bolts. The shear force generated by slippage along the interface is assumed to have a linear relationship with respect to the relative slipping distance between the rock bolt and the rock. The linear elastic criterion is applied to determine the material behavior of rock bolts before the axial stress reaches the yield value. The pullout tests are simulated to verify the coupling algorithm and the effects of the proposed rock bolt elements. Parametrical studies are also carried out to analyze the effectiveness of the rock bolts under various end conditions, joint locations and bond stiffness. In addition, the performance of the rock bolt during the interface debonding is analyzed using two types of constitutive laws, i.e., the friction law and the reduction law. The simulation results show that the proposed rock bolt models can predict the shear forces and axial loading along the rock bolts.     

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Glacial change in the vicinity of Mt. Qomolangma （Everest）, central high Himalayas since 1976

Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping (TM) and multi-spectral-scanner (MSS) images from Mt. Qomolangma (Everest) National Nature Preserve (QNNP), central high Himalayas for 1976, 1988 and 2006, we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that (1) the glacial area in 2006 was 2710.17 ± 0.011 km² (about 7.41% of the whole study area), and located mainly to the south and between 4700 m to 6800 m above sea level; (2) from 1976 to 2006, glaciers reduced by 501.91 ± 0.035 km² and glacial lakes expanded by 36.88 ± 0.035 km²; the rate of glacier retreat was higher in sub-basins on the southern slopes (16.79%) of the Himalayas than on the northern slopes (14.40%); most glaciers retreated, and mainly occurred at an elevation of 4700–6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; (3) increase in temperature and decrease in precipitation over the study period are the key factors driving retreat.     

REE Geochemistry of Moderate－and High－Sulfur Coals from North Shanxi,China

Contents of the rare-earth elements(REE) in two coal seams from North Shanxi Province,China,were determined using the instrumental neutron activation method.Based on the REE distribution tpatterns,and correlation analysis and cluster analysis,the main conclusions were drawn as follows.The REE contents are controlled mainly by the coal-forming environments,but might be affected by acidic solution Jeaching after peat sedimentation.The REE distribution patterns should be nearly the same in the sublayers of the same coal seam,and the occurrence of abnormal patterns might indicate the geological effect during post-sedimentation.The REE in coals are present mainly in the inorganic phase,and might be derived mainly from terrigenous detrital minerals.Some harmful elements,such as V,P,Mo,Cr,Cu,Mo,Th and Cd,might have cleaning potential during processing and dressing by washing because they are associated with REE.