敦煌-格尔木铁路沿线风动力环境特征

敦煌-格尔木铁路沿线地形复杂、起沙因素多变、沙源丰富,沙害问题日益严重。目前对其风沙活动规律还未有研究,不利于防沙工作的开展。为此,通过对自北向南的5个观测点（S1、S2、S3、S4、S5）风速和风向的观测、计算和分析,利用平均风速、起沙风况及输沙势对敦格铁路沿线的风动力环境特征进行研究。结果表明：S5、S4和S3的风况对铁路风沙灾害防治意义较大。S5年平均风速、起沙风频率和输沙势最大,春季风沙活动最为强烈,且风向单一、风力强劲,风沙运动方向基本与铁路垂直,沙粒易在铁路附近堆积。S4夏季风沙活动最为强烈;S3春季风沙活动最为强烈,且风向单一,S4和S3的风沙运动方向与铁路夹角小于90°,附近沙源广阔,铁路易受风沙侵蚀,阻碍交通运营。     

海表水温变动对东、黄海鲐鱼栖息地分布的影响

海表水温(SST)通常是表征鱼类栖息地分布的主要指标。本文根据1999—2007年我国大型灯光围网的鲐鱼生产统计数据,结合海洋遥感获得的SST,分析了渔汛期间鲐鱼栖息地的适宜SST范围,探讨了SST变动情况下鲐鱼栖息地的变化趋势。研究结果表明,东、黄海鲐鱼7—12月的适宜SST范围为15~30℃。根据政府气候变化专门委员会(IPCC)第四份评估报告,本文拟定4种SST上升的情况,即(1)每月平均SST+0.5℃;(2)每月平均SST+1℃;(3)每月平均SST+2℃;(4)每月平均SST+4℃。结果显示,东、黄海鲐鱼的潜在栖息有明显向北移动的趋势,并且栖息地面积逐渐减小。研究认为,全球气候变化引起的SST上升,可能会对近海鲐鱼栖息地造成严重的影响。     

阿尔金山前下—中侏罗统页岩气成藏地质条件分析

阿尔金山前侏罗系出露大套厚层的暗色泥页岩,生烃潜力优越,具备陆相页岩气形成条件,是有利的勘探接替区。通过野外地质调查、样品采集和测试分析,研究下—中侏罗统泥页岩的沉积展布、有机地球化学特征及储集性能,并探讨了该区页岩气的勘探潜力。研究表明: 富有机质泥页岩主要处于滨浅湖—半深湖相、沼泽相沉积环境中,其在平面上呈NE向展布,单层厚度和累计厚度均较大; 泥页岩的有机质类型主要为Ⅱ₁、Ⅱ₂型干酪根; TOC含量为0.55%~10%,平均为2.28%; 镜质体反射率(R_o)为1.0%~1.6%,平均为1.269%,处于成熟—高成熟阶段,为页岩气藏形成提供良好的生烃条件; 其矿物特征表现为脆性矿物含量高,大于51%,有利于后期的水力压裂改造和页岩气开采; 通过扫描电镜观察,泥页岩储层发育微孔隙及微裂缝,为页岩气提供了良好的储集空间和运移通道。初步预测,后期改造相对较弱的月牙山地区为页岩气勘探的有利目标区。     

市场分割与中国城市出口差异

出口贸易是中国经济增长的引擎,也是影响城市经济发展的重要因素。中国城市出口活动强度呈现由东向西逐渐递减的趋势,东部沿海地区的城市群表现最为优异。经济转型背景下地方政府采取的市场分割政策对中国城市出口差异有显著影响。基于新经济地理理论,在企业微观层面使用Heckman选择模型分析的结果表明：① 短期内,国内市场分割程度加剧导致企业因国内市场受限而替代性地进入国际市场以追求规模经济效益,从而通过增加出口企业数量提升城市出口表现;长期来看,市场分割限制了企业的规模经济效益和专业化分工能力,降低了出口企业的生产率和国际竞争力,从而损害城市出口贸易的可持续发展;这一机制还受到企业所有制及地理区位的影响。② 市场分割对企业出口行为的扭曲程度依外资企业、国有企业、私营企业的顺序递增。③ 在中国中部地区,改善省际交通条件有助于缓解国内市场分割对企业出口行为的扭曲作用,在东部和西部地区则不明显。     

Petrography,chemical composition,and Raman spectra of chrome spinel: Constraints on the diamond potential of the No. 30 pipe kimberlite in Wafangdian,North China Craton

Conventional diamond exploration seldom searches directly for diamonds in rock and soil samples. Instead, it focuses on the search for indicator minerals like chrome spinel, which can be used to evaluate diamond potential. Chrome spinels are preserved as pristine minerals in the early Paleozoic (∼465 Ma), hydrothermally altered, Group I No. 30 pipe kimberlite that intruded the Neoproterozoic Qingbaikou strata in Wafangdian, North China Craton (NCC). The characteristics of the chrome spinels were investigated by petrographic observation (BSE imaging), quantitative chemical analysis (EPMA), and Raman spectral analysis. The results show that the chrome spinels are mostly sub-rounded with extremely few grains being subhedral, and these spinels are macrocrystic, more than 500 µm in size. The chrome spinels also have compositional zones: the cores are classified as magnesiochromite as they have distinctly chromium-rich (Cr₂O₃ up to 66.56 wt%) and titanium-poor (TiO₂ < 1 wt%) compositions; and the rims are classified as magnetite as they have chromium-poor and iron-rich composition. In the cores of chrome spinels, compositional variations are controlled by Al³⁺-Cr³⁺ isomorphism, which results in a strong Raman spectra peak (A_1g mode) varying from 690 cm⁻¹ to 702.9 cm⁻¹. In the rims of chrome spinel, compositional variations result in the A_1g peak varying from 660 cm⁻¹ to 672 cm⁻¹. The morphology and chemical compositions indicate that the chrome spinels are mantle xenocrysts. The cores of the spinel are remnants of primary mantle xenocrysts that have been resorbed, and the rims were formed during kimberlite magmatism. The compositions of the cores are used to evaluate the diamond potential of this kimberlite through comparison with the compositions of chrome spinels from the Changmazhuang and No. 50 pipe kimberlites in the NCC. In MgO, Al₂O₃ and TiO₂ versus Cr₂O₃ plots, the chrome spinels from the Changmazhuang and No. 50 pipe kimberlites are mostly located in the diamond stability field. However, only a small proportion of chrome spinels from No. 30 pipe kimberlite have same behavior, which indicates that the diamond potential of the former two kimberlites is greater than that of the No. 30 pipe kimberlite. This is also supported by compositional zones in the spinel grains: there is with an increase in Fe³⁺ in the rims, which suggests that the chrome spinels experienced highly oxidizing conditions. Oxidizing conditions may have been imparted by fluids/melts that have a great influence on diamond destruction. Here, we suggest that chrome spinel compositions can be a useful tool for identifying the target for diamond potential in the North China Craton.     

Delineating groundwater potential zones in a hard-rock terrain using geospatial tool

Abstract

Geospatial techniques have become one of the leading tools in the field of natural sciences for assessment, monitoring and management of natural resources, particularly in groundwater research. The paper discusses the demarcation and assessment of groundwater potential zones using geospatial techniques in the Deccan Volcanic Province of Maharashtra, India, using multi-criteria analyses. The study incorporates integration of thematic information (geomorphology, lithology, drainage density, slope and lineaments) in a GIS environment in order to identify groundwater potential zones. The methodology adopted can be used as a rapid assessment tool in groundwater exploration and is helpful in predictive groundwater resource management. Multi-criteria evaluation techniques were used to integrate all the thematic layers. Individual themes and their corresponding categories were assigned a knowledge base ranking from 1 to 5, depending on their importance for groundwater potential. Using the Raster calculator tool in Arc GIS software, all thematic maps were integrated to produce a composite groundwater potential map of the study area. The identified groundwater potential zones were classified into four classes, from excellent to poor. The generated groundwater potential zones were validated with field checks and borewell/dugwell yield data, and showed consistency with the observations.

Citation Singh, P., Thakur, J. K., and Kumar, S. (2013) Delineating groundwater potential zones in a hard-rock terrain using geospatial tools. Hydrological Sciences Journal, 58 (1), 1–11.     

基于广义位势理论的弹塑性模型的修正方法

广义位势理论为岩土材料的本构关系研究指出了更开阔的数学背景。基于广义位势理论可以构造出基于应力空间的模型,也可构造出基于应变空间的模型,利用两者之间的对称关系,把常规基于应力空间的模型直接转换到应变空间中,对本构模型自身无需做任何改动。基于广义位势理论也可以对已有的本构模型进行修正,比如,可基于广义位势理论对剑桥模型进行修正,这种修正可使模型利用三轴试验的部分成果,比单纯使用压缩试验的成果要好一些。另外,也初步探讨了模型的三维化问题。     

莱西市建设“阳光”土地市场的探索

培育规范土地市场是深化土地使用制度改革的一项重要内容。莱西市国土资源局土地储备中心坚持规范与搞活并举,积极培育土地"阳光市场",使土地使用制度更加健全、规范、有序,为促进莱西市经济和社会发展做出了积极的贡献。     

溶质势对地表蒸发速率的影响

针对盐碱化土壤地表蒸发速率研究的不足,以表层土壤为研究对象,采用土壤蒸发试验和数学模型相结合的方法分析了溶质势对地表蒸发速率的影响。结果表明:当土壤中盐分没有沉淀结晶时,溶质势是盐分引起地表蒸发速率降低的主要原因;溶质势越低,蒸发速率下降比例越大,该下降比例与溶质势有近似线性关系,但同时还受到空气温度与相对湿度、土壤温度以及土壤基质势等因素的影响;当表层土壤存在水盐补给时,地表蒸发速率总是变化趋向于水分补给速率,但含盐土壤蒸发速率变化较慢,而且若补给水分中含盐,那么其稳定蒸发速率会低于水分补给速率。     

EFFECTS OF TROPOPAUSE AND POTENTIAL VORTICITY ANOMALY ON FRONTOGENESIS*

A two-dimensional,semi-geostrophic numerical model incorporating the tropopause and stratosphere is used to investigate the effects of a positive potential vorticity anomaly and latent heat release on the frontogenetic process and the structure of the resulting frontal zone.It is demonstrated that(1) the inclusion of tropopause and stratosphere significantly changes the frontal structure only in the upper levels;(2) a clearly defined quasi-equivalent barotropic structure and a region of upward motion of finite width appear when a positive potential vorticity anomaly exists on the warm side of the maximum baroclinity in the lower troposphere,especially when it is located on the south edge of the baroclinic zone;(3) the above mentioned structure deteriorates as the frontogenesis proceeds in a dry atmosphere but can be maintained in a moist frontogenetic process with condensational heating;(4) the combination of a positive potential vorticity anomaly and the latent heat release is able to accelerate the frontogenesis significantly with the time needed to form an intense frontal zone reduced to less than 15 h.The results have significant theoretical importance in understanding the complex nature of frontal structure and frontogenesis,especially in understanding the dynamic structure of the subtropical frontal zone observed during early summer over East Asia.