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41.
断裂带同震温度响应,可在震后钻孔测温中获得并识别,为发震断层摩擦特性与发震机制等基础研究提供了非常独特的思路和有效手段.集集、汶川及日本东北大地震后,实施了台湾车笼埔断层钻探项目(TCDP)、汶川地震断裂带科学钻探工程(WFSD)和日本海沟快速钻探计划(JFAST).钻孔测温结果表明:滑移面上下5~20m范围内存在温度正异常,这是同震摩擦生热所致,该机制已被广泛认识和接受;同时,距滑移面20~60m范围内也存在明显的温度负异常,但其成因机制几乎还未被真正关注和认识.虽然温度负异常峰值只有正异常峰值的1/4~1/3,但温度负异常分布范围却是正异常分布范围的3~4倍,即正、负温度异常区对应的总能量基本相当.因此,断裂带震后钻孔测温中的负异常及其成因不容忽视.在详细分析几种可能的同震温度负异常机制后(如岩层热物性分布差异、流体运移、表面自由能增大及同震应力释放),发现能在理论、实验及野外观测上都得到支撑的普适性机制只有同震应力释放.这可能是断裂带震后温度负异常的主要原因. 相似文献
42.
A new analytical solution is developed for describing groundwater level fluctuations in a coupled leaky confined aquifer system
which consists of an unconfined aquifer, confined aquifer, and an aquitard in between. The aquifer system has a tidal boundary
at the seashore, a no flow boundary at remote inland side, and a confined aquifer extending under the sea and terminated with
an outlet-capping. This new solution has shown to be a generalisation of most existing analytical solutions for a tidal aquifer
system which includes single confined and leaky confined aquifers. In addition, the solution is used to explore the influences
of the dimensionless leakance of the outlet-capping, the dimensionless hydraulic diffusivities, and the leakages of the inland
and offshore aquitards on the head responses in the leaky confined aquifer. 相似文献
43.
本文论述了37个氧离子作最紧密堆积的矿物,指出其平均折光率与结晶构造的定量关系。推导出“法扬斯常数”。阐明轻元素Li,Be,Na,Mg,Al对折光率的影响无显著差別;而第四周期的“重”元素如Ca,Sc,Ti,Cr,Mn,Fe都使折光率增高,这是与这些离子失去4s和3d电子有关,尤以失去3d电子对折光率增高影响最大。 相似文献
44.
45.
西藏高原及其附近的流场结构和对流层大气的热量平衡 总被引：58，自引：16，他引：58
本文利用1954—1956年的高空及地面记录,作出了平均流场,并计算了垂直速度、冷暖平流及辐射等,得出下面几点结论:1)冬季在1.5千米及3千米的西风,在高原西边有明显的分支,东边有明显的会合,且在东西两边各有一“死水区”(风速很小),在高原北面形成了高压脊,而在其南面形成了低槽,到了6千米除了二个“死水区”消失以外,其余基本上没有变化。2)夏季1.5千米及3千米在高原附近的流线,绕高原作气旋性旋转,而到了6千米则相反而呈反气旋性旋转,其中心在高原西南部分,且随高度增加而向西偏。3)夏季在高原上基本上是上升运动,可能达到9千米;冬季在高原上估计可能是下沉运动(除西南角有部分上升运动)。4)夏季可以肯定高原是一个热源,而冬季除了西南角有—部分是热源外,其他地区可能是一冷源。 相似文献
46.
正 INTRODUCTION In the year 1920, while carrying out a reconnaissance in North Kansu province, Dr. W. H. Wong' noticed in the field and later announced the importance of the diastrophism after the Tertiary red beds, to which the name 相似文献
47.
The main purpose of this study is to understand the stabilizing effect of ground-sills on the riverbed through a series of flume model experiments.From results,although check dams have the ability to control upstream sediment transport,the mass energy produced by the free fall of the overtopping discharge still causes strong local scour downstream of the structure,and this Scour lcads to the instability of the check dam.Therefore,this study conducted model experiments on various types of serial ground-sills to determine the appropriate spacing to best protect the downstream bed.Based on the observations and analysis of channel geomorphology and sedimentation,this study concluded the following results:1)Serial ground-sills reduces the sediment transport ability perfectly,especially under a mild channel gradient equipped with 2-4 times the average channel width interval.But for steep slopes,it is suggested that the proper spacing should be shortened to 1-2 times the average channel width.2)Ground-sills can effectively protect the streambed from scouring under a suitable equipped condition and the concepts of guiding scour and riverbed inertia were used in the analysis of optimal ground-sill spacing. 相似文献
48.
中国生产性服务业发展与空间分布 总被引：1，自引：0，他引：1
从分行业的角度探讨了中国生产性服务业的发展特征及其在城市体系中的空间分布。研究表明,中国生产性服务业的发展水平还处在初级阶段,虽然高级别生产性服务业增长较快,但是所占比重较小。空间分布上,生产性服务业倾向于集中在特大城市。由于其在经济发展中发挥重要的作用,这种分布特征重组了城市等级结构和城市之间的经济联系。随着中国经济的持续增长和政府的政策支持,对生产性服务业的需求将大大增加。全球化背景下,发展生产性服务业也成为重要的城市发展战略。但是,生产性服务业不均衡的分布格局决定了大城市和特大城市在新一轮的城市发展中具有更大的竞争力。因此,中小城市在发展生产性服务业时必须进行深入的分析,以免造成用地和资金的浪费。 相似文献
49.
Meridional zonation of the Barents Sea ecosystem inferred from satellite remote sensing and in situ bio-optical observations 总被引：2，自引：0，他引：2
B. GREG MITCHELL ERIC A. BRODY EUENG-NAN YEH CHARLES MCCLAIN JOSEFINO COMISO NANCY G. MAYNARD 《Polar research》1991,10(1):147-162
The Barents Sea is a productive, shallow, high-latitude marine ecosystem with complex hydrographic conditions. Zonal hydrographic bands defined by a coastal current. North Atlantic Water, the Polar Front, and the seasonally variable marginal ice edge zone create a meridional zonation of the ecosystem during the spring-summer transition. The features reveal themselves in satellite imagery and by high-resolution (vertical and horizontal) physical-optical-biological sampling.
Surprisingly, the long-term (7-year) mean of Coastal Zone Color Scanner (CZCS) imagery reveals the Barents Sea as an anomalous "blue-water" regime at high latitudes that are otherwise dominated by satellite-observed surface blooms. A combination of satellite imagery and in situ bio-optical analyses indicate that this pattern is caused by strong stratification in summer with surface nutrient depletion. The onset of stratification of the entire region is linked to the extent of the winter ice edge: cold years with extensive sea ice apparently stratify early due to ice melt; warm years stratify later, perhaps due to weaker thermal stratification of the Atlantic waters (e.g. Skjoldal et al. 1987). The apparent "low chlorophyll" indicated by the CZCS 7-year mean is partly due to sampling error whereby the mean is dominated by images taken later in the summer. In fact, massive blooms of subsurface phytoplankton embedded in the pycnocline persist throughout the summer and maintain substantial rates of primary production. Further, these subsurface blooms that are not observed by satellite are responsible for dramatic gradients in the beam (c1 ) and spectral diffuse (k) attenuation coefficients. The Barents Sea exemplifies the need to couple satellite observations with spatially and temporally resolved biogeographic ecosystem models in order to estimate the integrated water column primary production, mass flux or spectral light attenuation coefficients. 相似文献
Surprisingly, the long-term (7-year) mean of Coastal Zone Color Scanner (CZCS) imagery reveals the Barents Sea as an anomalous "blue-water" regime at high latitudes that are otherwise dominated by satellite-observed surface blooms. A combination of satellite imagery and in situ bio-optical analyses indicate that this pattern is caused by strong stratification in summer with surface nutrient depletion. The onset of stratification of the entire region is linked to the extent of the winter ice edge: cold years with extensive sea ice apparently stratify early due to ice melt; warm years stratify later, perhaps due to weaker thermal stratification of the Atlantic waters (e.g. Skjoldal et al. 1987). The apparent "low chlorophyll" indicated by the CZCS 7-year mean is partly due to sampling error whereby the mean is dominated by images taken later in the summer. In fact, massive blooms of subsurface phytoplankton embedded in the pycnocline persist throughout the summer and maintain substantial rates of primary production. Further, these subsurface blooms that are not observed by satellite are responsible for dramatic gradients in the beam (c
50.
水田在休耕期间蓄水,除了可维持水田原有之生态机能外,亦可增加土壤水分涵养与补注地下水.利用砂箱来模拟休耕田区中打入砂桩以补注地下水时,砂桩存在对灌溉水中之溶质在土壤中传输之影响.由试验结果得知当砂桩贯穿牛踏层时可增加水分入渗速率约40倍,相对的,砂桩亦加速溶质在不同土壤层间之传输速率,尤其在牛踏层下方之土壤为砂层时,其影响更为显著.因此,蓄水过程中需注意水源之品质,以避免土壤与地下水受污染. 相似文献