不同初始饱和度红砂岩冻融后物理力学性质研究

对不同初始饱和度红砂岩冻融循环前后进行物理及力学试验研究,探讨初始饱和度对红砂岩冻融损伤的影响。本文设定红砂岩试样初始饱和度为20%、40%、60%、80%、100%,冻融次数设定为20次,对冻融前后试样分别测定质量、纵波波速以及进行单轴压缩试验。试验结果表明：1）冻融后不同初始饱和度红砂岩的物理性质发生变化,纵波波速降低、质量减小,但变化程度不同;2）随饱和度的增大,试样经冻融后峰值强度和弹性模量均呈降低趋势,但只有饱和度大于60%时,降低趋势较明显。本文研究为寒区隧道及地下工程建设以及岩土地质灾害监测与治理提供理论依据和试验基础。     

X-ray activity from different types of stars

X-ray emission is an important indicator of stellar activity. In this paper, we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars. We provide a sample including 1259 X-ray-emitting stars, of which 1090 have accurate stellar parameter estimations. Our sample size is much larger than those used in previous works. We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars. We interpret that this bimodality is due to two subpopulations with different coronal heating rates. Furthermore, using the full widths at half maxima calculated from Hα and Hβ lines, we show that these stars in the inactive peaks have smaller rotational velocities. This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity. We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line, and find a tight relation between the coronal and chromospheric activity indicators.     

应用经验正交函数估算顶部电离层电子密度剖面

本文基于IRI模型、地面数字测高仪和GNSS TEC数据,提出了一种利用经验正交函数（Empirical Orthogonal Function,简称EOF）估算顶部电离层电子密度剖面的方法,并将其应用于美国Millstone Hill测高仪和GNSS数据以估算顶部电离层电子密度剖面.通过将估算的临界频率、峰值高度、400 km以上电子密度分别与测高仪实测临界频率、测高仪实测峰值高度以及非相干散射雷达实测400 km以上电子密度作对比以对方法的有效性进行验证.统计结果显示估算临界频率、峰值高度与测高仪实测数据基本一致,400 km以上估算电子密度相较于非相干散射雷达实测的绝对误差平均值仅是测高仪推算400 km以上电子密度绝对误差平均值的一半左右.所以本文提出的方法可以更加精确地估算顶部电离层电子密度.

     

青田山口叶蜡石传压介质初步研究

采用青田山口叶蜡石作为超高压高温合成金刚石的传压介质，分析了其主要化学成分和矿物组成。对青田山叶蜡石粉压块粒度效应进行了研究，确定了该传压介质的粒度组成。超高压高温人造金刚石试验表明，青田山口叶蜡石的传压介质理想，金刚石合成效果较好。     

Phytoplankton biomass size structure and its regulation in the Southern Yellow Sea (China): Seasonal variability

Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters, as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006–2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 1.42 and 1.27 mg m⁻³, respectively. Conversely, in the winter and spring, the average Chl a levels were only 0.98 and 0.99 mg m⁻³. Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters. The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients, temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions, hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton.     

Groundwater sustainability and groundwater/surface-water interaction in arid Dunhuang Basin,northwest China

The Dunhuang Basin, a typical inland basin in northwestern China, suffers a net loss of groundwater and the occasional disappearance of the Crescent Lake. Within this region, the groundwater/surface-water interactions are important for the sustainability of the groundwater resources. A three-dimensional transient groundwater flow model was established and calibrated using MODFLOW 2000, which was used to predict changes to these interactions once a water diversion project is completed. The simulated results indicate that introducing water from outside of the basin into the Shule and Danghe rivers could reverse the negative groundwater balance in the Basin. River-water/groundwater interactions control the groundwater hydrology, where river leakage to the groundwater in the Basin will increase from 3,114?×?10⁴ m³/year in 2017 to 11,875?×?10⁴ m³/year in 2021, and to 17,039?×?10⁴ m³/year in 2036. In comparison, groundwater discharge to the rivers will decrease from 3277?×?10⁴ m³/year in 2017 to 1857?×?10⁴ m³/year in 2021, and to 510?×?10⁴ m³/year by 2036; thus, the hydrology will switch from groundwater discharge to groundwater recharge after implementing the water diversion project. The simulation indicates that the increased net river infiltration due to the water diversion project will raise the water table and then effectively increasing the water level of the Crescent Lake, as the lake level is contiguous with the water table. However, the regional phreatic evaporation will be enhanced, which may intensify soil salinization in the Dunhuang Basin. These results can guide the water allocation scheme for the water diversion project to alleviate groundwater depletion and mitigate geo-environmental problem.     

Wave Propagation Modeling and Amplitude-Variation-with-Offset Response in a Fractured Coalbed

Coalbed methane can be detected employing the amplitudevariation-with-offset technique. However, there are two issues in applying this technique to a coalbed: strong azimuthal anisotropy resulting from high-density fractures, and the seismic response being composed of many or several individual reflections within the coalbed. To overcome these difficulties, we present an exact solution for reflections in extensive dilatancy anisotropy media. First, we build a three-layer model and simulate the wave propagation in this model. Then we derive an exact P- and converted S-wave reflection coefficient equation based on boundary conditions. Finally, substituting given model parameters into the exact equation, we obtain the variation in the reflection coefficient with incidence angle. The results show that the fracture factors, wavelet frequency and thickness of the coalbed have different effects on the reflection coefficient. Furthermore, we create a synthetic seismogram by forward calculation, and the result fits well with results of the exact equation.     

压力及流体对岩石孔隙结构与黏弹性的影响规律研究:理论模型及实验观测

地质成因和构造/热应力导致地壳岩石中的孔隙结构（裂隙和粒间孔）的变化.影响岩石黏弹性的因素包括压力、孔隙度、孔隙中包含的流体和孔隙几何形状等.相对于岩石中的硬孔隙,岩石黏弹性（衰减和频散）受软孔隙（裂隙）的影响更大.本文选取三块白云岩样本,进行了不同围压和流体条件下的超声波实验测量.利用CPEM（Cracks and Pores Effective Medium,裂隙和孔隙有效介质）模型获得了岩石高、低频极限的弹性模量,并通过Zener体（标准线性体）模型将CPEM模型拓展到全频带而得到CPEM-Zener模型,用该模型拟合岩石松弛和非松弛状态下的实验数据,本文得到平均裂隙纵横比和裂隙孔隙度以及纵波速度和品质因子随频率的变化关系.结果表明,饱水岩石的平均裂隙纵横比和裂隙孔隙度均高于饱油岩石,随着压差（围压和孔隙压力的差值）的增加,饱油岩石中的裂隙首先闭合.并且压差在70 MPa以内时,随着压差增大,岩石的平均裂隙纵横比和裂隙孔隙度在饱水和饱油时的差值增大,此时流体类型对于岩石裂隙的影响越来越显著,此外,对饱水岩石,平均裂隙纵横比随压差增加而增大,这可能是由于岩石中纵横比较小的裂隙会随压差增大而逐渐趋于闭合.在饱水和饱油岩石中,裂隙孔隙度和裂隙密度都随着压差增加而减小.通过对裂隙密度和压差的关系进行指数拟合,本文获得压差趋于0时的裂隙密度,且裂隙密度随孔隙度增大而增大,增大速率随压差增加而降低.针对饱水和饱油的白云岩样本,CPEM-Zener模型预测的纵波频散随压差增大而减小,此变化趋势和实验测得的逆品质因子随压差的变化关系基本一致,由此进一步验证了模型的实用性.本研究对岩石的孔隙结构和黏弹性分析以及声波测井、地震勘探的现场应用有指导意义.     

2014年中国气候概况

2014年,全国平均气温较常年偏高0.5℃,与1999年并列为1961年以来第六暖年;四季气温均偏高。全国平均降水量636.2 mm,接近常年,比2013年偏少3%;降水时空分布不均,辽宁、北京和河北偏少明显,冬、春、夏三季降水量均接近常年同期,秋季偏多。华南前汛期开始早、雨量多;西南雨季开始晚、结束早、雨量少;梅雨区降水量南多北少,江淮出现空梅;华北雨季不明显,出现空汛;华西秋雨开始早、结束晚、雨量多。夏季副热带高压脊线位置偏南,南海夏季风爆发晚,东亚夏季风强度略偏弱。2014年,我国气候属正常年景,极端天气气候事件少于2013年,暴雨洪涝、干旱等灾害偏轻,因灾造成死亡人数和受灾面积明显偏少,气象灾害属于偏轻年份。     

淹水解除后互叶白千层幼苗光合特性的恢复

为了优选用于河岸、库岸等间歇性淹水地区植被恢复的适生树种,研究了30d完全淹水解除后互叶白干层(Melaleuca alternifolia)幼苗气体交换特性、叶绿素荧光特性和质膜透性的恢复情况.在全淹30d及退水后70d的恢复生长过程中,互叶白干层成活率为100％.经过30d的全淹处理,互叶白干层的叶绿素含量、净光合...