松辽盆地白垩系青山口组黑色页岩的形成环境及海水侵入的底流模式

通过对中央坳陷区两口钻井剖面和东南隆起区野外露头剖面的沉积学、矿物学和地球化学研究，认为松辽盆地白垩系青山口组黑色页岩形成于稳定分层的湖相环境；周期性海水注入形成的底流是导致水体分层和黑色页岩沉积的重要因素。     

Tropospheric ozone profiles near equator and meteorological parameters

This is a study of ozone profile shapes in the 800 to 100 millibar range obtained with balloonsonde data over Trivandrum (8.5° N) during 1975–76 and possible associations of these shapes to some meteorological parameters.Whereas monotonic ozone profiles were noted with clear weather conditions, those associated with cloud cover show three basic anomalous features. Some bulges of increased values are observed in the range of 800 to 500 mb. In the 500–100 mb range, short range or localized cloud cover or passing weather disturbances are associated with fluctuation patterns in the ozone profile and an average depleted value of ozone. The fluctuations are also associated with changing wind speed and direction at these heights.Possible causative mechanisms are discussed. Lightning associated with thundestorm, producing additional CO and NO are sought to interpret the bulges at lower heights. The decrease in values as well as the fluctuation patterns are suggested as due to possible incursion of water vapour from troposphere to stratosphere in the tropical region and dynamical effects associated with it.     

Paleolimnology of the McMurdo Dry Valleys,Antarctica

The McMurdo Dry Valleys presently contain more than 20 permanent lakes and ponds, which vary markedly in character. All, with the exception of a hypersaline pond, have a perennial ice-cover. The dry valley lakes, and lakes in other ice-free regions of continental Antarctica, are unique on this planet in that they consistently maintain a thick year-round ice cover (2.8–6.0 m) over liquid water. The persistent ice covers minimize wind-generated currents and reduce light penetration, as well as restricting sediment deposition into a lake and the exchange of atmospheric gases between the water column and the atmosphere. From a paleolimnological perspective, the dry valley lakes offer an important record of catchment and environmental changes. These lakes are also modern-day equivalents of periglacial lakes that were common during glacial periods at temperature latitudes. The present lakes are mostly remnants of larger glacial lakes that occupied the valleys in the past, perhaps up to 4.6 Ma ago. Two of the valleys contain evidence of being filled with large glacial lakes within the last 10000 years. Repeated drying and filling events since then have left a characteristic impression on the salt profiles of some lakes creating a unique paleo-indicator within the water column. These events are also marked in the sediments by the concentration and dilution of certain chemical constituents, particularly salts, and are also corroborated by carbonate speciation and oxygen isotope analysis. Stratigraphic analysis of dry valley lake sediments is made difficult by the occurrence of an old carbon reservoir creating spurious radiocarbon dates, and by the high degree of spatial variability in lake sedimentation. From a biological perspective, the lakes are relatively simple, containing various taxa of planktonic and benthic microorganisms, but no higher forms of life, which is an advantage to paleolimnologists because there is no bioturbation in the sediments. Useful biological paleo-indicators found in the sediments include cyanobacterial filament sheaths, diatom frustules and other eukaryotic algal cells, protozoan cysts, photosynthetic pigments, and minerals (e.g. carbonates) associated with microbial activity. Future work will benefit from fully characterizing the connection between the ice covers, environmental conditions, and paleo-indicators, thereby allowing refinement of inferences made concerning the paleoenvironment. New dating techniques need to be tested in this environment to overcome the problems associated with radiocarbon dating. The establishment of a detailed and focused paleolimnological campaign is proposed.     

30-year response to damming of a Mediterranean river in California,USA

Dry Creek is a major tributary of the Russian River in Northern California (USA) that has experienced hydrologic and morphologic alterations after the closure of Warm Springs Dam in 1983. Our objective is to present a detailed diagnosis of the modification of the creek’s flow and sediment regimes, and interpret the alterations regarding the ecomorphologic evolution previously observed in the creek. Statistical analysis of the river’s flow and sediment series indicates that dam operation has had significant impacts on the magnitude and frequency of occurrence of the highest floods, and the magnitude, variability, and duration of low and very low flows. Similarly, sediment concentration and discharge have also experienced major alterations. Loss of habitat complexity for native flora and fauna (especially endangered salmonids), channel incision, and vegetation encroachment are some of the negative trends found for the creek over the last 30 years, since river regulation began. We discuss the present dynamics of the river and propose, on that basis, the improvement of its hydromorphic functioning as part of future large-scale restoration initiatives.     

Impacts of headcut height on flow energy,sediment yield and surface landform during bank gully erosion processes in the Yuanmou Dry‐hot Valley region,southwest China

To quantify the changes in flow energy, sediment yield and surface landform impacted by headcut height during bank gully erosion, five experimental platforms were constructed with different headcut heights ranging from 25 to 125 cm within an in situ active bank gully head. A series of scouring experiments were conducted under concentrated flow and the changes in flow energy, sediment yield and surface landform were observed. The results showed that great energy consumption occurred at gully head compared to the upstream area and gully bed. The flow energy consumption at gully heads and their contribution rates increased significantly with headcut height. Gully headcuts also contributed more sediment yield than the upstream area. The mean sediment concentrations at the outlet of plots were 2.3 to 7.3 times greater than those at the end of upstream area. Soil loss volume at gully heads and their contribution rates also increased with headcut height significantly. Furthermore, as headcut height increased, the retreat distance of gully heads increased, which was 1.7 to 8.9 times and 1.1 to 3.2 times greater than the incision depth of upstream area and gully beds. Positive correlations were found between energy consumption and soil loss, indicating that energy consumption could be used to estimate soil loss of headcut erosion. Headcut height had a significant impact on flow energy consumption, and thus influenced the changes in sediment yield and landform during the process of gully headcut erosion. Headcut height was one of the important factors for gully erosion control in this region. Further studies are needed to identify the role of headcut height under a wide condition. Copyright © 2018 John Wiley & Sons, Ltd.     

Linearized amplitude variation with offset and azimuth and anisotropic poroelasticity

The normal-to-shear weakness ratio is commonly used as a fracture fluid indicator, but it depends not only on the fluid types but also on the fracture intensity and internal architecture. Amplitude variation with offset and azimuth is commonly used to perform the fluid identification and fracture characterization in fractured porous rocks. We demonstrate a direct inversion approach to utilize the observable azimuthal data to estimate the decoupled fluid (fluid/porosity term) and fracture (normal and shear weaknesses) parameters instead of the calculation of normal-to-shear weakness ratio to help reduce the uncertainties in fracture characterization and fluid identification of a gas-saturated porous medium permeated by a single set of parallel vertical fractures. Based on the anisotropic poroelasticity and perturbation theory, we first derive a linearized amplitude versus offset and azimuth approximation using the scattering function to decouple the fluid indicator and fracture parameters. Incorporating Bayes formula and convolution theory, we propose a feasible direct inversion approach in a Bayesian framework to obtain the direct estimations of model parameters, in which Cauchy and Gaussian distribution are used for the a priori information of model parameters and the likelihood function, respectively. We finally use the non-linear iteratively reweighted least squares to solve the maximum a posteriori solutions of model parameters. The synthetic examples containing a moderate noise demonstrate the feasibility of the proposed approach, and the real data illustrates the stabilities of estimated fluid indicator and dry fracture parameters in gas-saturated fractured porous rocks.     

Analysis of rainfall variability over Tanzania in late austral summer

利用站点观测资料和再分析资料,采用相关分析,Morlet小波功率谱分析和复合分析等方法,研究了 1961-2011年南半球夏季后期(1-3月)坦桑尼亚降水的年际变化特征,并探讨了相关的大气环流和海温异常情况,以及坦桑尼亚干,湿年发生的机制.研究结果表明:坦桑尼亚1-3月降水变化存在显著的2-8年的年际变化周期和8-12...     

深层喷粉搅拌桩在地基加固工程中的应用研究

通过深层喷粉搅拌桩在榆林地区中级法院住宅楼地基加固工程中的成功应用 ,从设计、施工工艺、检测及技术经济综合分析提出了条基下单排或双排布桩的新思路及有关参数计算方法和验算过程。     

分离自桉树枯叶拮抗菌株的鉴定及拮抗性试验

从桉树枯叶中分离到的4株微生物菌株,对好食脉孢霉(Neurospora sitophila)具有拮抗作用。其中ED013、ED018和ED015抑菌圈之间差异不显著,与对照无菌水和多菌灵有极显著性的差异。ED014抑菌圈比前3个菌株效果差,但也与照无菌水和多菌灵有极显著性的差异。根据形态特点及生理生化测定结果鉴定4株菌株属于芽孢杆菌(Bacillusspp.)。