THE NATURE AND EXTENT OF A STRATIGRAPHICAL BREAK IN THE CAMBRO-ORDOVICIAN LIMESTONES OF NORTHERN ANHUI,AND ITS BEARING UPON THE SYSTEMATIC CLASSIFICATJON OF THE CAMBRO-ORDOVICIAN STRATA

Those who have followed the historical development of the systematicclassification of the old Palaeozoic rocks in Europe would undoubtedly wellremember how the Ordovician became recognized as a well-defined,independ-     

Turbulence Modelling of A Lock-Release Oil Slick

1 .IntroductionWiththe rapidincrease inthe scale of offshore oil depletion and marine oil transport ,the devas-tating and obnoxious effects of marine oil pollution due to oil spills become a matter of internationalconcern,and corresponding numerical simul…     

Study of Bed Friction Factor for the Wu River Estuary

1 .IntroductionThe Wu River systemis the most important estuary river in central Taiwan.Its tidal wave canrange over 5 meters .Itis considered as one of the most magnificent scenesin Taiwan.The understand-ing of the tidal flowof the estuaryis essential to…     

Three-dimensional saltating processes of multiple sediment particles

The purpose of this study was to investigate the interacting mechanism between the saltating particles near a channel bed. A three-dimensional real-time flow visualization technique was developed to measure the interparticle collision behaviors during the saltating process. Based on the experimental data, the distribution of the collision points was found to be symmetric. This confirms the assumption that the projections of the collision points onto the reasonable plane are uniformly distributed. A three-dimensional saltating model was also developed. This model produced satisfactory results. The model is able to simulate the continuous saltating trajectories of several particles. The simulated dimensionless saltating height, longitudinal and vertical saltation velocity components were found to increase as the dimensionless particle diameter and the dimensionless flow transport capacity parameter increase, while the simulated lateral saltation velocity component varies inversely with the dimensionless flow transport capacity parameter. A regression equation for the bed load transport rate was also obtained.     

澳门土壤剪切波速的相关性分析

土壤的剪切波速(VS),是抗震设计的一个重要参数,但有关澳门土层的相关资料则十分稀少。研究的主要目的是根据近期野外测试的结果,探讨澳门土层的VS与标准贯入试验的打击锤数(N)的关系,并以简单之幂函数建立VS与N值的关系式。作为澳门轻轨交通系统之勘察计划,研究进行了五组下孔法(DH),地震波圆锥触探试验(S-CPT)以及标准贯入试验(SPT)的测试。根据试验结果所得的关系式估算剪切波速高于较澳门轻轨设计大纲的建议值,而使用另一有关澳门土层的数据库来验证新的关系式,亦可获得合理的决定系数。     

Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials

Abstract— Primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids, but O‐isotopic analyses show only a modest heavy‐isotope shift, interpreted as indicating modification in the nebula. To understand the isotopic effects of asteroidal alteration, we take the L‐group ordinary chondrites weathered in Antarctica as an analogue. The data show that alteration is a two‐stage process, with an initial phase producing only a negligible isotopic effect. Although surprising, a possible explanation is found when we consider the alteration of terrestrial silicates. Numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates. We observe a similar texture. Alteration involves a restructuring of clay minerals along these narrow channels, in which access of water is restricted. The clay shows a topotactic relationship to the primary grain, which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original O structure by the clay. Our data suggests the latter: with extensive inheritance of structural polymers by the weathering product, the bulk O‐isotopic composition is comparatively unaffected. This offers an explanation for the lack of an isotopic effect in the weathering of the L chondrites. If substantial modification of chondritic materials may occur without a pronounced isotopic effect, it also reconciles existing O analyses of CV chondrites with an asteroidal model of aqueous alteration.     

Australasian microtektites in the South China Sea and the West Philippine Sea: Implications for age,size, and location of the impact crater

Abstract— Microtektites from two deep‐sea cores in the South China Sea and the West Philippine Sea are identified as belonging to the Australasian tektite strewn field based on the morphology, chronostratigraphic occurrence, and geographical location of these microtektites. The higher concentrations of microtektites (>1000/cm²) in the marginal seas of the western Pacific, with the peak concentration in the South China Sea, support the hypothesis of a large impact crater in Indochina. These two new occurrences lead to a more precise dating of the impact event at 793 ka, whereas the size of the Australasian source crater on the Indochina Peninsula is estimated to be 90–116 km.     

Differentiations of geographic distribution and subsistence strategies between Tibetan and other major ethnic groups are determined by the physical environment in Hehuang Valley

The people of the Tibetan Plateau have received extensive attention from scholars because of their unique adaptability to the low temperature and anoxic environments. However, the Tibetan communities and their habitats in the low-altitude regions of the plateau have rarely been studied in a scientific manner. Based on the extraction of geographic information of 197 towns in the Hehuang Valley and on variance analysis, this study examines the habitats and subsistence strategies of the Tibetans and other major ethnic groups in the low-latitude region of the Tibetan Plateau. Our statistical results show that the annual average temperature of Tibetan habitats in the Hehuang Valley is relatively high. The relatively warm environment of the valley allows the Tibetans in that area to cultivate wheat and barley and raise cattle and sheep—a subsistence strategy significantly different from that of other Tibetans in the high-altitude regions in the Tibetan Plateau. In addition, the Tibetan communities in the Hehuang Valley include similar agri-pastoral ethnic groups (including Hui and Salar), both of which adopt similar subsistence strategies. The agricultural ethnic groups (Han and Tu) live in a relatively cool and humid environment facilitating agricultural production, while the agri-pastoral ethnic groups (Tibetan, Hui, and Salar) inhabit relatively warm and arid environment in the valley. Due to the lack of agricultural activities, agri-pastoral groups must also engage in animal husbandry to supplement their diet. In the Ando Tibetan region, the subsistence strategies of the ethnic groups are closely related to their physical environment.Those ethnic groups communicate among themselves, integrate, and influence each other, resulting in a diversified culture. This study proves that the habitat variation at a regional scale corresponds significantly to the variation of subsistence strategies. Our findings may further refine knowledge about the human-environmental relationships of Tibetans and lead future research towards using quantitative methods to analyse the intersection of physical environment and ethnic groups' distribution.     

光降解-过硫酸钾方法分析水中溶解有机磷

对紫外(UV)光降解-过硫酸钾方法分析溶解有机磷的条件进行比较分析,在UV/加热条件下溶解有机磷的氧化率最高.进一步考察氧化剂的酸碱性和浓度对溶解有机磷氧化率的影响.Cl-和海水介质可以使溶解有机磷的氧化率显著降低.可以通过改变UV灯的功率、反应时间、反应温度、氧化剂等条件提高溶解有机磷的氧化率.