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1.
《Limnologica》2021
Karst springs represent valuable and often the most threatened habitats in the riverine landscape. Unlike other stream habitats, they have several specifics that determine their insularity in the river continuum, e.g., high seasonal thermal and chemical stability. The presented study aimed to find out the taxonomical and functional richness of three groups of aquatic insects (Ephemeroptera, Plecoptera and Trichoptera) in the Western Carpathians karst springs, as well as uncover the mechanism of the EPT community assembly. Low within-site species richness was generally found, however, there was high between-site diversity and thus high total diversity of the studied groups of benthic invertebrates as well. Species richness of the EPT community was higher in larger and colder springs: those with lower concentrations of CO2 and Fe, as well as higher concentrations of SO42−. Analysis of functional richness, as well as functional dispersion, did not reveal any clear assembly mechanism in the spring EPT community; however, both analyses indicated a higher proportion of environmental filtering there. Unlike the taxonomic richness, the functional richness of the EPT community was significantly higher in small and medium springs with higher water temperatures, as well as in springs with the presence of deadwood. Between-site dissimilarities in the functional composition of EPT were significantly correlated with environmental differences of springs, which determined variables such as spring size and temperature, as well as the concentration of CO2 and SiO2. 相似文献
2.
Mesozoic radiolarian chert from the middle sector of the Yarlung Zangbo suture zone,Tibet and its tectonic implications 总被引：1，自引：1，他引：1
ZHU Jie DU Yuansheng LIU Zaoxue FENG Qinglai TIAN Wangxue LI Jinping WANG Changping 《中国科学D辑(英文版)》2006,49(4):348-357
The middle sector of the Yarlung Zangbo suture zone stretches over 200 km long from Ngamring through Geding to Rinbung, roughly along Yarlung Zangbo River valley (Fig. 1). This belt resulted from the closure of the Tethyan ocean and the collision be- tween Indian plate and Lhasa block[1―8]. Lots of works demonstrated that rifting of the Tethyan basin in southern Tibet started from Triassic time. Initial oce- anic crust appeared in the Late Jurassic, and then ex- perienced a rapid sprea… 相似文献
3.
Geophysical prospection employing magnetometry and electromagnetic measurements has been applied in and around two small sized pyramids of Hellenikon and Ligourio in Argolid, Greece. The magnetic anomalies appropriately assessed were interpreted as possible archaeological targets. Subsequent test excavations revealed the presence of room foundations and parts of walls, as well as a plethora of ceramic ware. Typological study of the ceramics classified them to as early as the proto-Helladic period and to as late as the first centuries A.D. The earlier periods have been also confirmed by a novel application of thermoluminescence (TL) dating of ceramics and the megalithic stones themselves. The present results question earlier attempts classifying these pyramids at the Classical period and favour much earlier periods. 相似文献
4.
地层渗透率与水合物含量关系的模拟研究(英文) 总被引：1，自引：1，他引：0
本文通过人工变换T2分布和建立管-球模型模拟法研究含水合物地层渗透率与水合物含量之间的关系。首先,在渗透率的模拟试验中,我们改变了束缚水与可动水的比例、总孔隙度以及与之关联的T2分布。试验结果表明,相对渗透率与水合物含量之间的关系受到这些因素的制约。随后,我们用管-球模型表示水合物生长的孔隙空间,并把水合物的生长过程看成是向孔隙空间随机扔小球的过程。在此过程中,采用两种方法计算渗透率,一是Schlumberger’sT2公式(即SDR模型),二是Darcy定律与Poiseuille流动方程相结合的方法。前人的实验研究表明,在一定的水合物含量范围内,渗透率基本保持不变。以此为参考,我们将计算结果与之进行比较。我们发现,采用SDR模型时,渗透率的数值模拟曲线与Masuda模型N=15时的结果相近。而采用Darcy定律时,渗透率模拟值较高,但与实验结果的趋势相一致,都会出现渗透率的平直阶段。尤其,当水合物晶体在孔隙体内优先生成时,优先的概率越高,渗透率的平直范围越大。 相似文献
5.
本文从地貌、地质、地球物理和地震活动等方面,论证了一条由地垒、地堑系组成的、纵贯中国东部的巨型活动性深断裂带。 这是一条以张扭性为主、差异升降强烈的追踪断裂带。它控制着沉积岩相、地貌水系和岩浆活动,尤其是作为一条超基性岩带,可为寻找有关矿产提供标志;同时也是一条构造地震带 相似文献
6.
Mining,Environmental, Petroleum,and Engineering Industry Applications of Electromagnetic Techniques in Geophysics 总被引：6，自引：1，他引：5
Electromagnetic (EM) techniques are extremely important as a direct detection geophysical tool utilized in the base metal
industry. They were developed in countries such as Canada, whose thin conductive weathering overburden did not hamper the
penetration of EM signals and enabled exploration to depths on the order of 300 m. As a result, EM techniques were used widely
in North America and Scandinavia for many years before they became common in countries with a thick conductive overburden,
such as Australia. The 1980s and 1990s have seen the use of EM methods move from anomaly finding to mapping, as well as the
development of better, faster and more accurate computer modelling algorithms. A review of EM papers, for the years 1998 to
2002, showed that most dealt with EM techniques as mapping tools. Airborne, ground and marine EM techniques are still being
developed, as are data processing and interpretation software. The advent of robust 2-D and 3-D computer modelling and inversion
algorithms has led to the acceptance of EM methods as a mapping tool for many environmental and petroleum industry applications,
a trend which is expected to increase. 相似文献
7.
中央级救灾物资储备仓库在地震紧急救援中的作用 总被引：11，自引：0，他引：11
为了使灾民尽快得到物资救援，中央在天津、黑龙江、沈阳、合肥、郑州、武汉、长沙、南宁、西安建立了中央级救灾储备物资代储单位。本文介绍这些仓库的设置、构建、管理、现状和需要解决的问题。 相似文献
8.
Gaboury Benoit Jon M. Schwantes Gil S. Jacinto Margaret R. Goud-Collins 《Marine pollution bulletin》1994,28(12):754-759
Mining operations in Palawan, Philippines, resulted in cinnabar (HgS) mine tailings being used to build a 600 m long peninsula in Honda Bay. Samples collected from the peninsula as well as sediments from the surrounding waters had elevated mercury levels as high as 570 ppm. Natural processes are transporting mercury as much as 10 km from the peninsula, mainly in a coastwise direction, and preferentially associated with fine-grained, organic-rich sediments. Depth of penetration into sediments exceeds 10 cm near the source. As the HgS is transported away from the peninsula, it is rapidly altered to more bioavailable forms; 50% conversion occurs within a distance of only 10–40 m. 相似文献
9.
Significance of fossilized microbes from the Cambrian stromatolites in the Tarim Basin,Northwest China 总被引：2，自引：0，他引：2
Samples of the Cambrian microbial dolomites were collected from Penglaiba section,a well-exposed stratigraphic section in the northwestern area of the Tarim Basin.This study provides an analogue for mediated dolomites that can precipitate in microbial mats and biofilms.The Cambrian stromatolitic dolomites were studied using high-resolution scanning electron microscopy.The results are as follows:(1)dolomites with 50 nm to 100 nm spherical nanostructures are aggregated into minerals of larger sphericities;(2)nanospherical dolomites of 50 nm to 170 nm diameter are densely arranged as dumbbell-shaped or chained aggregates;(3)silicified filaments,as well as dumbbell-shaped and chain arrangements,are preserved as important microstructures.On the basis of sedimentological,compositional,geochemical,and petrographic data,the microstructures were interpreted as nanoglobules that function as bacteria in the nucleation and filament mineralization stages.The microstructures function as such because they are wrapped in extracellular polymeric substance(EPS)or mucus and mineralized fossils.Silicification accounts for the exceptional preservation of microbial mat structures,including biofilms,as well as filamentous and coccoid microbes.In addition,EPS process is capable of binding different elements,with preference for Si,Mg,and Ca.Such suitable composition favors microbe mineralization and dolomite nucleation on organic substrates.These microscopic structures suggest bacterial mineralization and provide visual evidence for the origin of microbial dolomites. 相似文献
10.
《Marine pollution bulletin》2007,54(10-12):650-656
Reducing marine-based public health risk requires strict control of several attributes of seafood products, often including location and conditions of catch or aquaculture, processing, and handling throughout the supply chain. Buyers likely will also be interested in other attributes of these products such as eco-friendliness or taste. Development of markets for improved safety, as well as for other quality attributes, requires an effective certification and tracking of these attributes as well as their communication to buyers. Several challenges must be met if labeling, particularly consumer labeling, is to support the development of markets for improved seafood safety. 相似文献
11.
The process of aquifer recharge by flood events in an arid region was investigated as applied to the Hazeva Formation (the Karkom graben, the Wadi Paran watershed, Israel). The hydrological model was established as a complex system, with due regard for groundwater and transmission losses of surface runoff. It was based on a previously outlined hydrogeological model of the Karkom graben and a model of transmission losses in arid watercourses under conditions of data deficiency. Proceeding from calculation of groundwater balances, the contribution of surface runoff as a decisive balance component was confirmed. The main characteristics of aquifer regimes, such as changes in storage volume and groundwater level, as well as lateral flow, were all found to be dependent upon the net extraction rate, i.e. pumpage discounting replenishment by flood events. Analysis and physical interpretation of model parameters enabled assessment of the influence of groundwater extraction on aquifer recharge. This became apparent as increasing absorption capacity and recharge availability of the aquifer as a result of the groundwater abstraction. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
12.
Andreas J. Kappos 《地震工程与结构动力学》1991,20(2):167-176
Criteria to be used for the analytical prediction of collapse of R/C buildings subjected to earthquake excitation are suggested. It is attempted to include in the criteria as many of the parameters involved as possible, while keeping the complexity, as well as the cost of analysis reasonably low. Two combined collapse criteria are finally suggested, corresponding to member failure and storey failure. Using these criteria, quantitative estimations can be obtained of the actual values of behaviour factors (q-factors) used in modern seismic codes. The ground motion dependence of these factors, as well as the sensitivity of their calculated values to the assumption made about the stiffness of R/C members, is illustrated with reference to two typical structures. 相似文献
13.
The Estuarine Quality Paradox, Environmental Homeostasis and the difficulty of detecting anthropogenic stress in naturally stressed areas 总被引：2，自引：0，他引：2
Estuaries have long been regarded as environmentally naturally stressed areas because of the high degree of variability in their physico-chemical characteristics, for example oxygen, temperature and salinity in the water column and bed sediment dynamics. However, their biota is well-adapted to cope with that stress and so the areas may be regarded as resilient because of that inherent variability; their ability to absorb stress without adverse effects is regarded here as Environmental Homeostasis. Hence these areas may only be regarded as stressful for marine or freshwater-adapted organisms and that for estuarine organisms this environmental stress is regarded as a subsidy whereby they successfully capitalise on the stressful conditions. In addition, using examples of the estuarine fauna and flora, this article indicates that the characteristics of natural stress in estuaries are similar to those for anthropogenic stress. An over-reliance on ecosystem structural features, such as diversity, in quality indicators therefore makes the detection of the anthropogenic stress more difficult. This difficulty is termed the Estuarine Quality Paradox. Because of these difficulties, the article argues that functional characteristics either as well as or rather than structural ones should be used in detecting environmental perturbations in estuaries. 相似文献
14.
José A. Ramos 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):33-52
Most lumped rainfall-runoff models separate the interflow and groundwater components from the measured runoff hydrograph in an attempt to model these as hydrologic reservoir units. Similarly, rainfall losses due to infiltration as well as other abstractions are separated from the measured rainfall hyetograph, which are then used as inputs to the various hydrologic reservoir units. This data pre-processing is necessary in order to use the linear unit hydrograph theory, as well as for maintaining a hydrologic budget between the surface and subsurface flow processes. Since infiltration determines the shape of the runoff hydrograph, it must be estimated as accurately as possible. When measured infiltration data is available, Horton’s exponential infiltration model is preferable due to its simplicity. However, estimating the parameters from Horton’s model constitutes a nonlinear least squares fitting problem. Hence, an iterative procedure that requires initialization is subject to convergence. In a similar context, the separation of direct runoff, interflow, and baseflow from the total hydrograph is typically done in an ad hoc manner. However, many practitioners use exponential models in a rather “layer peeling” fashion to perform this separation. In essence, this also constitutes an exponential data fitting problem. Likewise, certain variogram functions can be fitted using exponential data fitting techniques. In this paper we show that fitting a Hortonian model to experimental data, as well as performing hydrograph separation, and total hydrograph and variogram fitting can all be formulated as a system identification problem using Hankel-based realization algorithms. The main advantage is that the parameters can be estimated in a noniterative fashion, using robust numerical linear algebra techniques. As such, the system identification algorithms overcome the problem of convergence inherent in iterative techniques. In addition, the algorithms are robust to noise in the data since they optimally separate the signal and noise subspaces from the observed noisy data. The algorithms are tested with real data from field experiments performed in Surinam, as well as with real hydrograph data from a watershed in Louisiana. The system identification techniques presented herein can also be used with any other type of exponential data such as exponential decays from nuclear experiments, tracer studies, and compartmental analysis studies. 相似文献
15.
František Hrouda 《Surveys in Geophysics》1982,5(1):37-82
Magnetic anisotropy in sedimentary rocks is controlled by the processes of deposition and compaction, in volcanic rocks by the lava flow and in metamorphic and plutonic rocks by ductile deformation and mimetic crystallization. In massive ore it is due to processes associated with emplacement and consolidation of an ore body as well as to ductile deformation. Hence, it can be used as a tool of structural analysis for almost all rock types. Morcover, it can influence considerably the orientation of the remanent magnetization vector as well as the configuration of a magnetic anomaly over a magnetized body. For these reasons it should be investigated in palaeomagnetism and applied geophysics as well. 相似文献
16.
Single span highway bridges of composite construction are idealized as beams as well as orthotropic plates. A standard HS–20–44 highway vehicle is represented by a planar, two-axle, sprung mass system with frictional device. The response equations are derived in terms of the natural modal co-ordinates of the bridge and of displacement co-ordinates of the vehicle. The road surface irregularities, generally found at the junctions of the approach road and bridge ends, are idealized as a 45° ramp. The maximum impact factors for bending moment and deflection are obtained due to the ramp and in combination with the braking of vehicle for symmetric as well as essentric loading of the vehicle. 相似文献
17.
介绍了多道中心式记录强震仪的工作原理,性能及技术指标,给出了仪器的设计方法、理论分析和具体电气功能控制、时间服务系统等结构框图。文中还介绍了强震仪在地震现场观测获取的很有价值的地震记录。 相似文献
18.
In accordance with the natural, geographic, and ecological characteristics of the Taihu Lake Basin, and the relation between the water body of Taihu Lake and its surrounding environment, an area, which has tight relevance with the water environment of Taihu Lake, was token as the main investigation region. The area was named as the Taihu Lake Region. Some factors, such as TN, TP, CODCr that characterized the main environmental problem, the eutrophication were selected when conducted the pollution sources investigation on in Taihu Lake Region. The categories, distribution, pollution contribution to the Lake of dijferent pollution sources, as well as the routes of pollutants entering the Lake were basically made clear. Pollution sources that must be preferentially controlled and the direction of controlling those main pollutants, such as TN, TP, CODCr, were proposed. Base on the investigation, a series of eco-systematic approaches for controlling Taihu Lake eutrophication were put forward. They are ecosystem regulation, nutrient substances transferring along food chain, trophic masse degrading step by step along the route from a pollution source to the Lake, building ecological preventive zone of the Lake, as well as the ecological measures for point sources treatment and so on. 相似文献
19.
Sanhita Majumdar Pijush Kanti Mandal Sudip Kumar Das Rabindranath Majumdar 《洁净——土壤、空气、水》2013,41(3):291-297
Carbon bearing materials derived from rice husk (RH) have long been recognized as sorbents for diverse chemicals – both organic and inorganic. This work presents an overview of studies demonstrating a single step process of carbonization of chemically pretreated RH to produce metal impregnated silica‐carbon char designated as silicarbon materials that can be utilized in sorbing out water‐borne organic and inorganic hazardous substances (such as phenol, hexavalent chromium, fluoride, and arsenic) and air‐borne volatile organic chemicals (such as acetone, chloroform, benzene, and pyridine). The metal‐impregnated silicarbon solids derived from RH appear to constitute renewable, low‐cost, user‐friendly, and efficient materials for control systems for indoor air contamination and for industrial as well as non‐industrial hazardous aqueous pollution. 相似文献