Research Progress of Leaf-wax Hydrogen Isotope Paleoaltimetry

Leaf waxes/lipids which are derived from terrestrial higher plants are ubiquitous in fluvial, lake, and marine sediments. N-alkanes are an important component of leaf waxes. Modern leaf wax n-alkanes from terrestrial higher plants are characterized with long chains with 27 to 33 carbon atoms (nC₂₇-nC₃₁) and high carbon preference index (CPI) values (>5). The hydrogen isotopes in n-alkanes are determined by meteoric water compositions, which makes them a potential proxy in paleoaltimetry studies. The lapse rates at which n-alkane hydrogen isotopes in modern soils change with altitude vary in different areas, implying that local calibration has to be conducted. The enrichment due to evapotranspiration and difference in fractionation during biosynthesis also influence n-alkane hydrogen isotopes values. When using long-chain n-alkanes to reconstruct paleoaltitude, many factors such as paleoclimate, paleolatitude and paleobotany should be considered.     

Discrete element simulation of dynamic semi-circular bend flexure tests of rocks using split Hopkinson pressure bar

The semi-circular bending (SCB) using a split Hopkinson pressure bar system appears to be a promising method for measuring dynamic flexural strength of rock materials due to its distinct advantages. The quasi-static analysis is adopted for determining the dynamic flexural strength, of which several vital prerequisites have not been thoroughly examined yet. In this study, dynamic flexure tests regarding dynamic force equilibrium, interfacial friction effects, and energy partitioning are numerically investigated based on discrete element method (DEM) modeling. Results show that by virtue of the ramped wave loading, the force equilibrium of the specimen can be effectively achieved and the rupture is precisely measured to synchronize with the peak force, both of which guarantee the quasi-static data reduction method employed to determine the dynamic flexural strength; while the opposite occurs for the test under a rectangular wave loading. Furthermore, dynamic flexural strengths obtained by the numerical SCB tests exhibit approximately linear rate dependence that is identical with the experimental results. The interfacial friction, which is found to significantly influence the measuring results for rather high loading rates, contributes to enhancing the rate dependence of flexural strength and must be taken into account in dynamic flexure tests. In addition, energy partitioning is first numerically performed in the dynamic SCB tests and the nominal fracture energy manifests an S type of rate dependence with loading rates.     

Quality and quantity of pre-drainage methane and responding strategies in Chinese outburst coal mines

The potential sources of recharge of both water and solutes to the Quaternary aquifer in the area between Ismailia and El Kassara canals in northeastern Egypt include seepage from the irrigation canals and conduits, return flow after irrigation in the cultivated fields, local precipitation, and the upward flow of groundwater from the underlying Miocene aquifer system. Water isotopes, solute concentrations, and sulfate isotopes were used to investigate the geochemical sources, reactions, and the impacts of the hydraulic connections among recharge sources. The obtained results indicate a minimal influence of the underlying Miocene aquifer as a water and solute source while old and new contributions from the irrigation canals represent the main sources of recharge. The chemical reactions responsible for the chemical constituents and salinity in the aquifer include silicate weathering, evaporite dissolution, and carbonate precipitation. Most of groundwater samples appear to lie at/or close to equilibrium with montmorillonite, kaolinite, and illite where clay minerals are quite common in the local soils of the Quaternary aquifer.

     

2010年秋季南海北部浮游植物群落结构研究

2010年10月26日-11月24日在南海北部进行了浮游植物群落结构的调查,共鉴定浮游植物4门70属204种(包括未定种12种),浮游植物以硅藻为主,其物种数为146种,其细胞丰度占总浮游植物细胞丰度的93.17%;甲藻次之,其物种数为51种,占总浮游植物细胞丰度的0.63%;金藻门3属4种及蓝藻门2属3种;蓝藻门中以红海束毛藻(Trichodesmium erythraeum)为主。调查区浮游植物的细胞丰度介于0.06×103~107.50×103 cells/L之间,平均值为5.00×103 cells/L。海南岛东北部和粤东近岸表层浮游植物丰度较高。垂直分布上,表层和25 m层的浮游植物细胞丰度较高。浮游植物主要优势种类有菱形海线藻(Thalassionema nitzschioides)、舟形藻(Navicula spp.)、中肋骨条藻(Skeletonema costatum)、旋链角毛藻(Chaetoceros curvisetus)、斯氏几内亚藻(Guinardia stolterforthii)、具槽帕拉藻(Paralia sulcata)等。调查区表层和5 m层Shannon-Wiener多样性指数平均值分别为3.14和2.83,Pielou均匀度指数平均值分别为0.73和0.77;两种指数在表层和5 m层均表现出较高的一致性。环境分析表明除硅酸盐外,浮游植物细胞丰度与其他环境因子均呈极显著性的相关性,主要受到氮元素及磷酸盐的共同限制作用。     

风浪和海洋飞沫对海表面拖曳系数和风廓线的影响

基于埃克曼理论,本文将波致应力和飞沫应力引入到海-气边界层的界面应力中,来研究海表面风浪和海洋飞沫对海-气边界层动量交换的影响,并得到修改后的埃克曼模型的理论解。波致应力是由风浪谱和波增长函数估计,并得到在中低风速下,波致应力、飞沫应力与湍流应力相比,对海表面拖曳系数和风廓线的影响非常小。当风速高于25米/秒时,海洋飞沫通过飞沫应力对海-气界面应力的作用远高于波致应力,以至于波致应力可以忽略。海表面拖曳系数在高风速下,随着风速的增大而减小。通过采用风浪谱的不同波龄,得到海洋飞沫的产生会导致海-气边界层风速的增加。最后,理论解与现场的观察数据进行了对比。对比后的数据表明,在中高风速下,飞沫对海-气边界层的影响远大于表面风浪。     

我国海上风电发展政策演变分析

海上风电是新能源和可再生能源发展的战略重点之一,目前我国海上风电发展已经取得一定成效,而且发展前景广阔。文章通过对我国海上风电发展现状和政策框架的深入研究,从政策背景、政策内容和政策实施评价3个方面分析我国海上风电发展政策演变历程,揭示其演变特征及存在的主要问题,提出关于我国海上风电发展政策的若干建议,以期为我国海上风电开发管理及政策制定提供参考借鉴。