南极普里兹湾夏季海冰边缘区内破碎海冰的分布特征          下载免费PDF全文

卢鹏  李志军  张占海  董西路 《水科学进展》2007,18(6):884-892

基于中国第21次南极考察中获得的69°00'S、76°24'E附近普里兹湾夏季海冰边缘区内破碎海冰的航拍照片,利用图像处理的方法从中提取了破碎海冰的若干几何参数,得到了海冰边缘区内随着与开阔水域距离增大,海冰面积、平均钳测直径等几何参数的变化规律。并按其尺寸的变化规律将海冰边缘区划分为边界区、过渡区和内部区三部分,其变化和波浪在冰边缘区中的衰减过程紧密相关。圆度的变化则说明海冰边缘区中海冰磨损最充分的地方是在冰间相互作用最明显的过渡区。另外,一种改进的幂函数分布和Weibull分布用来对破碎海冰尺寸的累积频率进行拟合,分布函数中各参数的变化情况很好的反映了海冰边缘区内破碎海冰的分布变化。其中,参数L_r随着与开阔水距离增加而增大(说明由于波能衰减导致可以出现的破碎海冰最大尺寸的增加);尺度参数L₀随着与开阔水距离增加而增大(反映了破碎海冰平均尺寸的增加以及由于波能的衰减而导致单位面积区域内尺寸较大的破碎海冰所占比例的增加);分布维数D随着与开阔水距离增加而减小(说明了由于波能的衰减导致破碎海冰所受约束条件的减弱);形状参数γ随着与开阔水距离增加而减小(说明了随着波能的衰减破碎海冰尺寸分布范围的增大)。  相似文献   

森林沼泽景观区区域化探新、旧方法技术应用效果对比     

王会锋  彭立华  王晓云  安兴  陈恩科 《陕西地质》2007,25(2):44-53

自森林沼泽景观区1∶20万区域化探工作开展以来,各个单位、不同阶段工作方法技术各有不同,工作效果不明显。中国地质科学院地球物理地球化学勘查研究所近年来通过研究制定了新的工作方法技术,通过应用取得了较好的效果,为此本文仅以内蒙古一二五公里幅1∶20万区域化探新、旧方法技术的应用效果对比进行初步探讨。  相似文献   

昌图县西山银金矿点成矿条件及找矿前景分析     

邵帅  吴平  赵东波  陈元江 《华南地质与矿产》2007,(4):14-19

辽宁昌图县西山银金矿点的北东与吉林省四平市山门银矿床相邻,区域上处在同一个构造单元内。通过对控矿因素、矿化特征、围岩蚀变等方面的综合分析和对比,认为两矿床(点)存在诸多相似之处,同受山门-叶赫韧-脆性剪切带的控制,前者是山门银矿床(带)的南延部分,找矿前景较大。  相似文献   

Synthesis,characterization of CdS/rectorite nanocomposites and its photocatalytic activity     

Jiangrong Xiao  Tianyou Peng  Dingning Ke  Ling Zan  Zhenghe Peng 《Physics and Chemistry of Minerals》2007,34(4):275-285

CdS/rectorite nanocomposite was synthesized via a cation-exchange reaction followed by a sulfurization process. The obtained samples were characterized by using X-ray diffraction (XRD), fourier transform infrared spectra (FTIR), transmission electron microscope (TEM), UV-Vis diffuse reflectance spectra (DRS), and thermal analysis. The measured results indicate that CdS species in the composites exist in the form of pillars and nanoparticles, the crystallized CdS particles are in the hexagonal symmetry. The photocatalytic activities of the pillared nanocomposite were enhanced significantly comparing with the bare rectorite and the pure CdS. Moreover, the photostabilities of the obtained nanocomposites are also better than that of the pure CdS due to the hosts retard the photocorrosion of the CdS.  相似文献   

威连滩冲沟砂黄土的风蚀与降雨侵蚀模拟实验   总被引：3，自引：0，他引：3  

宋阳  严平  刘连友  杨恒华  朱孟郡  杜建会  马玉凤 《中国沙漠》2007,27(5):814-819

 通过风洞与模拟降雨实验，研究了风力与降雨对青海省贵南县威连滩冲沟砂黄土的复合侵蚀作用。实验得出：①风蚀后的降雨使砂黄土表面在风干过程中形成了一层较为坚硬的结壳，增大了土壤的抗蚀性，降低了第二次风洞实验后期的风蚀率;②土壤水分与人为扰动是影响土壤风蚀的两个重要因素。当土壤水分较小时，风蚀率受人为扰动影响巨大;当土壤水分较大时，人为扰动对土壤风蚀的影响较小;③在持续降雨的实验条件下，砂黄土的产流、产沙量随着雨强的变化而改变。这种变化与表土的侵蚀率、可蚀性物质的多少、土壤水分以及土壤的入渗率等都有很大的关系。  相似文献   

近50年来新疆天山山区水循环要素的变化特征与趋势   总被引：2，自引：0，他引：2  

蓝永超  吴素芬  钟英君  韩萍  赵琪 《山地学报》2007,25(2):177-183

天山山区由于其特殊的地理位置与高海拔,成为新疆地表径流的主要产流区域。近几十年来,全球平均气温的持续上升对该区域气温、降水、径流等水循环要素产生重要的影响。根据天山南北坡有关水文气象台站的观测资料,系统地分析了该区域1960年代以来各水循环要素的变化特征与趋势。结果表明,受全球变暖的影响,1980年以来整个天山地区气温和降水均呈明显的上升趋势,其中10 a气温的升幅更为显著;对于降水而言,天山南坡降水增幅大于北坡,而南坡的西段是近10 a降水增幅最大的区域。受气温上升与降水增加的影响,天山地区出山径流总体上呈增加的趋势,其中,近10 a天山南坡中西段河流出山径流量增幅最为显著,平均增幅在30%以上。  相似文献   

Crustacean zooplankton distribution patterns and their biomass as related to trophic indicators of 29 shallow subtropical lakes   总被引：3，自引：0，他引：3  

Songbo Wang  Ping Xie  Shikai Wu  Aiping Wu 《Limnologica》2007,37(3):242-249

A comparative limnological study was carried out to present a snapshot of crustacean zooplankton communities and their relations to environmental factors to test whether there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with similar trophic conditions. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L⁻¹, and chlorophyll a from 0.7 to 146.1 μg L⁻¹, respectively. About 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, Moina micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. TP was a relatively better trophic indicator than chlorophyll a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic state. The lack of significant negative correlation between crustacean biomass and chlorophyll a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes.  相似文献   

气枪震源激发模式及应用   总被引：3，自引：5，他引：3  

罗桂纯  葛洪魁  王宝善  胡平  母红旺  陈颙 《中国地震》2007,23(3):225-232

气枪震源是一种重要的人工地震震源。气枪阵列理论的提出,使得气枪阵列设计技术日趋成熟,并能够在石油勘探和地球物理探测中得到更加广泛的运用。气枪震源在不同领域中应用时,需要不同的组合和激发模式,以适应不同的探测要求。加强主脉冲和加强气泡脉冲,是目前两种主要的气枪激发模式。通过比较研究两种气枪激发模式,讨论各种激发模式在激发时间、气枪间距、频率、分辨率等方面的差异,为气枪震源的广泛运用提供依据。  相似文献   

Effects of surface characteristics on infiltration patterns in an arid shrub desert   总被引：3，自引：0，他引：3  

Xin‐Ping Wang  Xin‐Rong Li  Hong‐Lang Xiao  Ronny Berndtsson  Yan‐Xia Pan 《水文研究》2007,21(1):72-79

Precipitation is often the sole source of water replenishment in arid and semi‐arid areas and, thus, plays a pertinent role in sustaining desert ecosystems. Revegetation over 40 years using mainly Artemisia ordosica and Caragana korshinskii at Shapotou Desert Experimental Research Station near Lanzhou, China, has established a dwarf‐shrub and microbiotic soil crust cover on the stabilized sand dunes. The redistribution of infiltrated moisture through percolation, root extraction, and evapotranspiration pathways was investigated. Three sets of time‐domain reflectometry (TDR) probes were inserted horizontally at 5, 10, 15, 20, 30 and 40 cm depths below the ground surface in a soil pit. The three sets of TDR probes were installed in dwarf‐shrub sites of A. ordosica and C. korshinskii community with and without a microbiotic soil crust cover, and an additional set was placed in a bare sand dune area that had neither vegetation nor a microbiotic soil crust present. Volumetric soil moisture content was recorded at hourly intervals and used in the assessment of infiltration for the different surface covers. Infiltration varied greatly, from 7·5 cm to more than 45 cm, depending upon rainfall quantity and soil surface conditions. In the shrub community area without microbiotic soil crust cover, infiltration increased due to preferential flow associated with root tunnels. The microbiotic soil crust cover had a significant negative influence on the infiltration for small rainfall events (～10 mm), restricting the infiltration depth to less than 20 cm and increasing soil moisture content just beneath the soil profile of 10 cm, whereas it was not as strong or clear for larger rainfall events (～60 mm). For small rainfall events, the wetting front depth for the three kinds of surface cover was as follows: shrub community without microbiotic soil crust > bare area > shrub community with microbiotic soil crust. In contrast, for large rainfall events, infiltration was similar in shrub communities with and without microbiotic soil crust cover, but significantly higher than measured in the bare area. Soil water extraction by roots associated with evapotranspiration restricted the wetting front penetration after 1 to 3 h of rainfall. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

酒泉地区香蕉上市量与气象灾害的关系及预警系统     

郭良才  石奋字  岳平  王月琴 《干旱气象》2002,20(2):14-15

文中通过对香蕉运输过程中气象灾害的分析 ,总结出了香蕉运输过程中气象灾害发生的规律 ,据此建立了一套防灾减灾的预警系统 ,并对采用该系统前后的气象灾害进行了对比分析  相似文献