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    共找到 天文地球相关的 248328篇文献

    Preparation of fermented tea from Grifola frondosa and determination of tea polyphenols content 收藏

    期刊: 地球科学前沿 刊期: 2017年第1期 作者: Zheng Qiuhua, Zheng Yize, Fangbaiyu, Zengsongrong 阅读量: 3647

    in order to tea polyphenols and its preparation method with further understanding of Maitake fermented tea, in order to lower the value of the Green Tea medium as the basis, and through the medium of training set for different formulations of tea, and then make the Grifola frondosa in the culture medium for fermentation and the growth situation observation, determined the best medium formula for the mycelial growth of Green Tea. On this basis, using the Folin phend method for the determination of tea polyphenols content to be. The results showed that flower fermented tea produced in the preparation of the ash tree, tea polyphenol content was 2.3%, compared to the ash tree flower before fermentation, the tea polyphenol degradation rate as high as 65.6%, After fermentation, the bitter taste of tea was diluted, and its taste and quality were improved significantly. 展开

    Grifola frondosa fermented tea tea polyphenols Folin phenol colorimetry

    Assessment of pollution levels and human health risk of heavy metals in dust deposited on Yerevan’s tree leaves (Armenia) 收藏

    期刊: 中国地球化学学报(英文版) 刊期: 2017年第1期 作者: N. Maghakyan 阅读量: 1829

    The total concentrations of Cd, As, Pb, Cr, Ni,Co, Zn, Cu, Ag, Hg, and Mo were determined in theatmospheric dust of the city of Yerevan by atomicabsorption spectrometry (AAnalyst PE 800). Heavy metalpollution levels were evaluated by calculating geo-accumulation(Igeo) and summary pollution (Zc) indices.Potential human health risk was assessed using the UnitedStates Environmental Protection agency’s human healthrisk assessment model. The results show that mean contentsof all elements tested except Ni and Cr were substantiallyhigher than local geochemical backgroundvalues. According to the Igeo, Yerevan territory is stronglyto-extremely polluted by As, Ag, Hg, Mo, and Cd. The Zcassessment indicated that very high pollution was detectedin 36 % of samples, high in 32 %, average in 12 %, andlow in 20 %. The health risk assessment revealed a noncarcinogenicrisk (HI[1) for children at 13 samplings sitesand for adults at one sampling site. For children the riskwas due to elevated levels of Mo, Cd, Co, and As, while foradults, only Mo. Carcinogenic risk ([1:1,000,000) of Asand Cr via ingestion pathway was observed in 25 and 14samples, respectively. This study, therefore, is the base forfurther detailed investigations to organize problematic siteremediation and risk reduction measures. 展开

    Urban dust · Heavy metals · Pollution levels · Health risk assessment

    Research progress on aging of organic pollutants in geosorbents: a review 收藏

    期刊: 中国地球化学学报(英文版) 刊期: 2017年第1期 作者: Xianjin An 阅读量: 1278

    Geosorbents are the main host of anthropogenicorganic pollutants and play a vital role in their fate andtransport in the natural environment. Soil and sediment arethe most common and abundant geosorbents in the naturalenvironment; their interactions with organic pollutants,especially sorption and desorption processes, have beenextensively studied from the perspectives of thermodynamicsand kinetics. Recently, the aging of organic pollutantsin geosorbents has drawn increased attention, leadingto an improved understanding of interactions betweenorganic pollutants and geosorbents and informing remediationcriteria. Aging has been deemed important in accuratelyassessing ecologic and health risks of organicpollutants, and both positive and negative impacts havebeen reported in studies of natural and artificial sorbents.This paper summarizes recent research progress on organicpollutant aging in geosorbents, including related mechanismresearch, influence factors, bioavailability assessments,and biological and physicochemical remediation ofaged organic pollutants. We also discuss issues in thecurrent research and bring forward suggestions for futurestudy. 展开

    Geosorbent · Aging effects · Bioavailability · Organic pollutants · Supergene processes

    Evaluation of hydrogeochemical characteristics and the impact of weathering in seepage water collected within the sedimentary formation 收藏

    期刊: 中国地球化学学报(英文版) 刊期: 2017年第1期 作者: M. V. Prasanna 阅读量: 3777

    A study was conducted by collecting eightseepage water samples that drain through the sedimentaryrocks, mainly sandstone and shale, to evaluate the hydrogeochemicalcharacteristics. The collected samples wereanalyzed for physico-chemical parameters using standardprocedures. Three water types were identified in the Piperplot and the hydrogeochemical evolution starts from a Ca–Cl facies (type 1) via mixed Ca–Mg–Cl and Ca–Na–HCO3facies (type 2) to Na–Cl facies (type 3). Increasing trend ofelectrical conductivity (EC) values were observed fromtype 1 water to type 3 water. Lower ionic concentrationswith an average EC value of 35.7 ls/cm in Ca–Cl faciesindicate the recharge water by monsoonal rainfall, and ionexchange/weathering process is reflected in the mixingzone. Higher ionic concentration with an average EC valueof 399 ls/cm is noted in Na–Cl facies, which indicates theion exchange during water–rock interaction. Higher logpCO2 values are also found in this facies, revealing thelonger residence time of seepage water in the rock matrix,which release more ions into the water. The relativemobility of elements during weathering suggest that theorder of mobility in both sandstone and shale isNa[Ca[Mg[K. It was observed that thehydrogeochemistry of seepage water is mainly controlledby the bedrock geology. 展开

    Hydrogeochemistry · Seepage water · Water– rock interaction · Weathering ·Mobility of elements

    Skarn mineralogy and its geological significance for the Tayuan (Cu–Mo)–Pb–Zn deposit, northern Daxinganling metallogenic belt 收藏

    期刊: 中国地球化学学报(英文版) 刊期: 2017年第1期 作者: Chao Li 阅读量: 3117

    The Tayuan (Cu–Mo)–Pb–Zn deposit is locatedin the northern part of Daxinganling, NE China. Lenticularore body occurs in the skarn zone. The skarn mineralsmainly include garnet, pyroxene, epidote and wollastonite.Electron microprobe analysis shows that the end memberof garnet is mainly andradite (Ad62–97Gr11–45), the pyroxeneis mainly diopside, and epidote is mainly clinozoisite.These characteristics indicate that the Tayuan polymetallicskarn deposit is mainly calcareous skarn. Sometimes thecontent zonation can be observed in garnets. With onegarnet crystal, content is shifty from the core to the rim. Ingeneral, the iron content in the core is higher than in theedge. The content in the garnet shows that the garnet in theTayuan deposit formed from weak oxidation in alkalineenvironment with the oxygen fugacity increasing, suggestingthat the hydrothermal fluid evolved from an acidicto a slight alkaline state. In the Tayuan polymetallicdeposit, the ratio of Mn/Fe in pyroxene is about 1.3, and ofMg/Fe, it is about 2. The components of garnet in theTayuan deposit plot in the field of the typical skarn Zn, Cu,Mo deposits in the world. 展开

    Skarn minerals · (Cu–Mo)–Pb–Zn deposit · Physical–chemical condition · Tayuan

    盐溶液中膨润土膨胀变形的分形模型 收藏

    期刊: 岩土力学 刊期: 2017年第1期 作者: 项国圣 阅读量: 1204

    当压实膨润土在蒸馏水中膨胀后,施加于膨润土颗粒上的有效应力通常被认为是外部施加的荷载,而当膨润土在盐溶液中膨胀时,膨润土颗粒所承受的有效应力还包括由孔隙水渗透吸力所引起的渗透应力。而压缩膨润土的蒙脱石孔隙比em 与膨润土颗粒承受的有效应力p 之间满足分形关系,该关系可用来计算膨润土的膨胀变形。通过对压实膨润土在盐溶液中颗粒的分散情况以及颗粒表面的分形特性,推导出该渗透应力的表达式,进而得出膨润土颗粒所承受的有效应力。将所提出的有效应力代入分形模型中,计算GMZ01 和MX-80 膨润土在不同浓度NaCl 溶液中的膨胀变形,将现有的两种膨润土膨胀试验结果与模型计算结果对比,发现具有较好的吻合度,在蒸馏水以及各浓度的盐溶液中膨润土的膨胀变形都可采用统一的em-p 曲线表示,表明提出的有效应力符合膨润土颗粒在盐溶液中的实际受力情况。分形模型为研究膨润土在盐溶液中的膨胀性质提供了有效的计算方法。 展开

    膨润土 膨胀变形 表面分维 分形模型 盐溶液 有效应力

    基于三维数字图像相关技术的脆性岩石破坏试验研究 收藏

    期刊: 岩土力学 刊期: 2017年第1期 作者: 马永尚 阅读量: 3164

    利用三维数字图像相关技术(3D-DIC)观测系统研究单轴压缩状态下带中心圆孔花岗岩岩板的破坏全过程,得到了含孔洞岩石破坏过程中观测面的三维全场位移和应变,不仅能够直观地反映岩石表面裂隙的产生、扩展及相互连通的演化过程,亦能够确定裂纹的位置、形态以及扩展方向等具体信息,还能重现加载过程中试样表面的压缩(平行荷载方向)、剥离(垂直荷载方向)、膨胀及剥落(垂直试样表面方向)。结果表明:3D-DIC 技术在岩土力学试验中有其独特的优势,岩石材料破坏过程中应变场的演化能较好地反映其内部裂纹的产生和扩展规律。根据全场应变云图可以判断岩石裂纹扩展演化的情况;裂纹的演化具有强烈的非线性特征,在试样接近破坏时形成的“X”型对称变形局部化带,最终只形成一条宏观破坏带,荷载方向、岩石结构及其内部的非均匀性都会对最终宏观破裂带的位置产生影响;利用3D-DIC 观测系统进行岩石变形破坏机制的研究是有效的,可为岩土介质宏细观变形破坏机制的研究提供重要的借鉴。 展开

    三维数字图像相关技术 带孔岩板 非接触 全场应变测量 裂纹扩展 破坏

    围岩-锚固体流变控制机制及支护最优化设计 收藏

    期刊: 岩土力学 刊期: 2017年第1期 作者: 罗生虎 阅读量: 3668

    针对巷道围岩的流变特性及其控制理论,通过黏弹性理论和非线性最优化原理,在考虑开挖面空间效应的基础上,研究围岩-锚固体的耦合作用机制,并建立巷道支护最优化设计模型。通过算例分析了支护时间、锚固体厚度、巷道半径以及原岩应力对围岩-锚固体流变特性和巷道支护最优化设计的影响。结果显示,支护时间、锚固体厚度、巷道半径以及原岩应力都与巷道围岩的稳定性有着密切的联系。巷道位移随着支护时间的增长、锚固体厚度的减小、巷道半径和原岩应力的增大而增大;当锚固体受力处于临界状态时,锚固体厚度随着支护时间的增大而减小,且当锚固体厚度较小时,锚固体厚度与支护时间近似呈线性关系。 展开

    围岩 黏弹性 耦合 最优化

    主应力轴变化下非共轴对砂土剪胀特性影响 收藏

    期刊: 岩土力学 刊期: 2017年第1期 作者: 熊 焕 阅读量: 3526

    传统塑性剪胀模型在描述应力比和塑性应变增量关系时都是基于共轴塑性流动法则,从而认为土体的剪胀性仅与应力比有关。大量试验结果表明,在涉及主应力轴变化的复杂应力条件下塑性流动过程中应力-应变是非共轴的,因而在分析砂土剪胀特性时非共轴是不可忽视的因素。为了研究主应力轴变化的复杂应力条件下非共轴对砂土剪胀特性的影响,利用空心圆柱仪对饱和砂土进行了一系列定轴剪切试验、纯主应力轴旋转试验以及组合加载试验。试验结果表明,不同应力路径下应力-应变非共轴都会引起剪胀曲线偏离Rowe 直线,通过Gutiereez 提出的考虑非共轴因子的修正剪胀方程可以修正非共轴引起的偏差,从而使得Rowe 剪胀方程适用于涉及主应力轴旋转等更加复杂的加载条件。 展开

    剪胀性 非共轴 主应力轴变化 应力比

    块石含量及形状对胶结土石混合体力学性能影响的大型三轴试验 收藏

    期刊: 岩土力学 刊期: 2017年第1期 作者: 金 磊 阅读量: 3554

    胶结土石混合体在自然界中分布广泛,为了揭示块石含量和块石形状对其力学特性的影响,开展了一系列室内大三轴试验研究。首先,通过掺有一定量水泥的土石混合体试样与未掺水泥的试样进行对比,以论证土石混合体有必要进一步划分为胶结土石混合体和无胶结土石混合体。然后,针对胶结土石混合体设计并进行了不同块石含量和块石形状的对比试验。最后,对胶结土石混合体力学特性的块石含量和块石形状效应进行了分析探讨。结果表明:水泥掺入比为3%的土石混合体试样较未掺水泥的试样强度和模量均有大幅提高,有明显的应变软化和局部化剪切带;在给定条件下,胶结土石混合体的峰值强度和脆性指数均随含石量的增加而减??;当含石量为40%时,块石为碎石的胶结土石混合体试样与块石为卵石的试样相比峰值强度略低,而残余强度略高;而当含石量为70%时,无论是峰值强度还是残余强度,块石为碎石的试样均比块石为卵石的试样大,围压较大时尤为明显。 展开

    胶结土石混合体 大三轴试验 含石量 块石形状

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