检索结果-南通市图书馆

Applying Empirical Methods to Assess the Internal Stability of Embankment Dam cores of Glacial Till

在线全文

学校读者我要写书评

暂无评论

Geomaterials 2015年第1期5卷 1-18页

作者： Hans Ronnqvist Peter Viklander Department of Civil Environmental and Natural Resources EngineeringLulea University of TechnologyLuleaSweden

This paper presents a database of glacial till gradations that are compiled from laboratory internal stability tests from the literature and from core soils of existing dams, some of which have experienced internal erosion. The potential internal instability of these gradations is assessed using empirical methods. Two approaches of evaluation are used: the Kenney-Lau method, which analyzes the shape of the gradation curve;and the Burenkova method, which uses factors of uniformity of the slope of the gradation. Although they include some uncertainties in terms of soils with fines, these methods, which are primarily developed from laboratory studies of sand and gravels, are used in engineering practice to evaluate widely graded soils that include fines, such as glacial tills. This study evaluates the glacial till gradations of the database using these approaches and discusses their applicability and relative predictive success. This study indicates that both the Kenney-Lau method and the Burenkova method have merit, but a closer analysis indicates that the Kenney-Lau approach has relatively better predictive ability based on the glacial till gradations analyzed in this study.

关键词： Internal Stability Internal Erosion cores Glacial Tills Embankment Dams

Geochemical Characteristics of Saturated Hydrocarbons from Strata Inferred from the Multitubular cores of the Prydz Bay and the Sources/Environmental Variations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Meteorological and Environmental Research 2019年第5期10卷 96-102页

作者： Yang Dan Zhang Yicheng Han Xinbin Zhao Jun Xu Xuedan Zhang Huijuan Zhang Haisheng Key Laboratory of Marine Ecosystem and Biogeochemistry Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China

The content and distribution of saturated hydrocarbons (n-alkanes,isoprenoid,steranes and terpanes) in the multitubular cores ANT29-M2 from the Prydz Bay of the Antarctic were analyzed using gas chromatography-mass spectrometry,and the organic matter sources,sedimentary environments and geochemical parameters of the sediments were *** results showed that the carbon number of the multitubular samples ANT29-M2 was between C14 and C32 with low-carbon single peak group and main peak carbon of C18 .n-alkane gas charomatography fingerprint spectra indicated that unmixable complex compounds displayed a significant bulge,and the obvious UCM shape suggested a large input of *** ∑C21^-/∑C22^+ values varied from 1.82 to 3.9,and C21^+C22 /C28 ^+C 29 values ranged from 1.26 to 6.30,indicating that the sedimentary organic matter mainly originated from marine *** CPI and OEP values varied from 1.54 to 2.29 and from 4.48 to 4.82,respectively,with a significant odd even ***/Ph values ranged from 0.34 to 0.76,significantly smaller than 1,with a clear distribution of C29 >C27 >C28 and C27 >C29 >C28 for regular steranes and a V-shaped C29 predominance and C27 *** indicated that the sedimentary organic matter in the Prydz Bay originated from a mixed marine/continental source,and was deposited under a strongly reducing *** maturity parameters of the sedimentary strata from the Prydz Bay displayed significant *** parameters of hopane C 32 22S/C 32 (22S+22R) and sterane C 29 αββ/(αββ+ααα) suggested a high maturity,but other geochemical parameters such as C29 ααα20S/C29 ααα(20S+20R),CPI and OEP reflected that those of columnar strata were within the range of modern marine sediments (lowly mature to immature),probably resulting from the development of microorganisms.

关键词： Prydz Bay Sediment cores Saturated hydrocarbons Geochemical characteristics Environmental significance

Study on Test Methods for Mechanical Properties of Semi-rigid Base cores of In-service Pavements

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Civil Engineering and Architecture 2018年第2期12卷 97-105页

作者： Song Bo Zhang Jin-xi Xue Zhong-jun Zhou Xu-li Zhang Tao School of Metropolitan Transportation Beijing University of TechnologyBeijing 100124China Beijing Board Engineering Quality Supervision Station Beijing 100076China

Compressive strength and compressive resilience modulus are two important parameters to measure the mechanical properties of semi-rigid *** test methods of semi-rigid base cores are different from those of the laboratory samples in terms of sample acquisition,sample selection and humidity ***-drilling location,size of core sample,smoothness and humidity conditions were *** test methods of compressive strength and compressive resilience modulus were *** research results show that compressive strength of lime fly-ash stabilized gravels base has a tendency of increasing during a long *** compressive resilience modulus increases significantly with compressive strength of semi-rigid *** compressive resilience modulus generally is 3-4 times than the recommended range of asphalt pavement design *** fluctuation range of compressive resilience modulus is obviously higher than the compressive *** compressive resilience modulus is more sensitive to the construction *** overall trend between the compressive resilience modulus and the back-calculation modulus is ***(falling weight deflectometer)back-calculation modulus can reflect the stiffness and bearing capacity of asphalt pavement.

关键词： Road engineering semi-rigid base cores compressive strength compressive resilience modulus test methods

Hierarchical cores Applied to an Analysis of Use of Technologies Level among Higher Education Students in Mexico

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Statistics 2014年第10期4卷 837-850页

作者： Francisco Casanova-del-Angel SEPI-ESIA Unit ALM of the Polytechnic Institute National Mexico City Mexico

Using the theory shown, cores Optimal Criterion, three factors from which hierarchical aggregation of variables under study was built, as well as hierarchical cores showing the level of use of pocket computing technologies by students. The principal factors influencing the level of use of pocket computing technologies among higher education students are analyzed from a theoretical aggregation development based on hierarchical cores. The theoretical part includes the development of an algorithm used to obtain an interesting class or partition from a hierarchy. The experimental work carried out included design, preparation and application of a questionnaire to higher education students in Mexico. A pilot test was carried out to check timing and repetition of questions. Data was recorded, validated, and mathematically and statistically analyzed.

关键词： Use of Technologies Higher Education Questionnaire Pocket Calculators Hierarchical cores

Geochemical distribution, fractionation, and sources of heavy metals in dammed-river sediments: the Longjiang River, Southern China

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Geochimica 2019年第2期38卷 190-201页

作者： Xiaolong Lan Zengping Ning Yizhang Liu Qingxiang Xiao Haiyan Chen Enzong Xiao Tangfu Xiao State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory for Water Quality and Conservation of the Pearl River Delta Ministry of Education School of Environmental Science and Engineering Guangzhou University

In the present study, six sediment cores were collected from six river-dammed reservoirs to reveal the geochemical distribution of heavy metals(As, Cd, Pb, Sb,and Zn) in the Longjiang River, South China, which is highly impacted by nonferrous metal mining and smelting activities. The sediments were geochemically characterized, combining geochemical analysis, sequential extractions, and210 Pb chronology. The results indicated that the river sediments were severely polluted by heavy metals in the order of Cd [ Zn & Pb & Sb [ As. These heavy metals generally exhibited relatively low enrichment in the upstream sediments because of the limited anthropogenic impact, but their abundances drastically increased in the midstream sediments due to local smelting activities. In downstream sediments, the heavy metal concentrations(except for Cd) decreased, owing to the effect of dam interception and detrital inputs. Cadmium levels tended to increase in downstream sediments, which were attributed to the intensive discharge of Cd during the pollution event in 2012. The sedimentary records were traced back to1985, and a significant decrease of heavy metal enrichments could be found after the year 2000, suggesting the enhancement of environmental management in this *** statistical results indicated that local metal smelting and mining activities were the main anthropogenic contributors for the enrichment of heavy metals in the dammed-river sediments. High enrichment factor and nonresidual fractions of heavy metals in local sediments may pose a direct threat to aquatic organisms. Cd presents significant danger because of its extreme enrichment and high labile fractions.

关键词： Heavy metals Fractionation 210pb dating Smelting and mining activities Sediment cores The Longjiang River

Distribution of eight heavy metals in the inner shelf sediments of East China Sea:Risk assessments and sources analysis

在线全文

学校读者我要写书评

暂无评论

Ecosystem Health and Sustainability 2021年第1期7卷 87-101页

作者： Chunjie Wang Zhangwei Wang Xiaoshan Zhang State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijingChina College of Resources and Environment University of Chinese Academy of SciencesBeijingChina

Although numerous studies on heavy metals(HMs)in sediments have been carried out in the East China Sea(ECS),the knowledge on the recent pollution levels of HMs in coastal region remains not well understood due to the rapid developments of urbanization in eastern *** this study,23 surface samples and 4 core samples are collected in the inner shelf of the *** average dry-weight concentrations follow the descending order of Zn,Cr,Ni,Pb,Cu,As,Cd,and Hg(103.6±26.0,42.8±12.4,37.0±9.1,34.7±11.1,19.5±10.3,15.7±11.6,0.056±0.017,and 0.041±0.017μg g^(−1),respectively).HMs concentrations share a similar spatial distribution pattern of TOC content with a decreasing trend from coastline to outer ***,HMs concentrations exhibit a decreasing trend from top to bottom sediments,especially for Hg at the open sites due to the wet and dry deposition of atmospheric Hg besides the riverine *** potential ecological risk indices(PERI)values in coastal sediments were about 2-4 times higher than those in open *** the Hg and Cd concentrations were lower by 2-3 orders of magnitude than those of other six metals,the PERI values of Hg(65.5)and Cd(52.1)were 3-40 times higher than those of *** hierarchical cluster result is consistent with the PCA result,suggesting that Hg,Cd,and As have similar sources and probably mainly originated from anthropogenic emissions.

关键词： Heavy metals spatial distribution cores environmental risk east China Sea

On multi-choice TU games arising from replica of economies

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2016年第3期31卷 307-319页

作者： TIAN Hai-yan LIU Jiu-qiang ZHENG Xiao-wei WANG Zhi-wei Department of Applied Mathematics Northwestern Polytechnical University School of Management Engineering Xi’an University of Finance and Economics Department of Mathematics Eastern Michigan University Mathematics and Information College Hebei Normal University

In this paper we derive a multi-choice TU game from r-replica of exchange economy with continuous, concave and monetary utility functions, and prove that the cores of the games converge to a subset of the set of Edgeworth equilibria of exchange economy as r approaches to infinity. We prove that the dominance core of each balanced multi-choice TU game, where each player has identical activity level r, coincides with the dominance core of its corresponding r-replica of exchange economy. We also give an extension of the concept of the cover of the game proposed by Shapley and Shubik （J Econ Theory 1： 9-25, 1969） to multi-choice TU games and derive some sufficient conditions for the nonemptyness of the core of multi-choice TU game by using the relationship among replica economies, multi-choice TU games and their covers.

关键词： multi-choice TU games cores dominance core Edgeworth equilibrium

Study on fragmentation of PELE against thin targets

在线全文

学校读者我要写书评

暂无评论

Journal of Beijing Institute of Technology 2011年第2期20卷 168-172页

作者：蒋建伟张谋门建兵王树有 State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology

The fragments mass and size from penetrator with enhanced lateral effect （PELE） perforating thin rolled homogenous armor （RHA） target was characterized through theoretical and numerical methods. An analytical model based on energy-limited spall （ELS） was proposed to predict fragments mass distribution of PELE with different cores and impact velocities. For different cores the expansion can be represented by a scaling factor l in the analytical calculation. The explicit finite-element （FE）-analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. By statistical distribution of ＂weak points＂ in numerical model of PELE, the dynamic fragmentation was delineated to simulate Flaw-limited spall as in real material. To verify the accuracy of theoretical calculation and validate numerical results, experiments of PELE perforating thin RHA target was setup, fragments were collected by using recovery cabin filled with foam and soft sands. Both energy limited spall theory and Flaw limited approach showed accurate results compared with experimental data.

关键词： PELE lateral effect cores natural fragments numerical simulation

Assessment of Toxicity Potential of Sedimentary PAHS from Refome Lake, South-East Nigeria over the Last Century

在线全文

学校读者我要写书评

暂无评论

Journal of Geoscience and Environment Protection 2020年第1期8卷 1-15页

作者： Inyang O Oyo-Ita Emmanuella E Oyo-Ita Ekpo O Ikip Bassey B Asuquo Orok E Oyo-Ita Environmental/Organic Geochemistry Research Group Department of Pure and Applied Chemistry University of Calabar Calabar Nigeria Xi’an Shiyou University Xi’an China

In this study, toxic equivalent factors and sediment quality guidelines were employed for the assessment of toxicity potential of PAHs in 2 sediment cores collected from the center (RC) and shoreline (RS) of Reforme lake, SE Nigeria over the last ~1 century. Boundary cross plots of isomeric ratios such as Ant/Ant + Phe (>0.1) vs. Fl/Fl + Pyr (>0.4) and BaA/BaA + Chry (>0.35) vs. Icdp/Icdp + Bper (>0.2) indicated biomass combustion/domestic coal utilization as the main sources of PAHs input. The result revealed toxicity unit indices (TU1, 1.22 - 1.57) for the two cores were above the thresholds of no effect. The highest TU1 value found in the near-bottom layer (RS5, 20 - 25 cm) of the RS corresponding to geological time-frame ~1930-1947 coincided with the period of inhabitation by the European settlers along the lake’s catchments when coal or coal products utilization for domestic and recreational purposes was at its peak. On the other hand, TU2 values were <1 at all depth intervals, revealing unlikely PAH effects to resident organisms. Total toxicity equivalency factors (TEqFs) for the surface sediment of RS and RC were 9.29 ng/g TEqFs and 9.16 ng/g TEqFs, respectively, and indicated that more attention should be paid to BaPyr accumulation in the lake’s sediment.

关键词： Toxicity PAHs Refome Lake Sediment cores Assessment Source