蔚县盆地中更新世哺乳动物化石新发现

1 研究目的(Objective) 蔚县盆地为典型的冀西北山间盆地,与阳原盆地仅一山之隔,二者共同组成了广义的"泥河湾盆地",盆地内广泛出露中更新统郝家台组(Qp2h)河-湖相沉积物.相比阳原盆地,蔚县盆地古生物化石研究程度较低.20世纪80年代,盆地北部(大南沟一带)出土具有上新世—早更新世面貌的小型哺乳动物化石,近...     

东北地区湿度梯度下的表土植硅体的空间分布规律

植硅体的现代过程研究是恢复古环境的基础,探讨表土植硅体分布及组合特征对环境因子的响应尤为重要。沿中国东北地区年均温为4 ℃等温线采集70块表土样品,研究了单一温度因素控制下表土植硅体的空间分布规律,以期获得不同类型植硅体对降水的响应。研究结果表明：所有表土样品中植硅体丰富且数量较多,主要有棒型、尖型、块状、扇型、扁平状、短鞍型、帽型、哑铃型、齿型、三棱柱型、导管型、硅质突起、硅化气孔、弓型和多面表皮植硅体;且主要以短细胞、棒型、尖型为主,其平均百分含量之和高达80.77%,块状、扁平状、扇型次之,其他类型的植硅体含量较少。方差分析结果表明：棒型、三棱柱型、硅质突起、哑铃型和扁平状在大兴安岭、松嫩平原和长白山之间存在显著性差异,且棒型、三棱柱型、硅质突起的百分含量与年降水量具有极显著的正相关性,哑铃型的百分含量与年降水量具有极显著的负相关性。总之,年均温为4 ℃等温线上70块表土样品中植硅体类型基本相同,但不同类型植硅体的百分含量存在差异,说明本研究区域内表土植硅体组合特征对降水的响应较为敏感。

     

多元门限回归模型的一种建模方法

本文根据门限自回归模型的基本思想[1]，提出一种多元门限回归模型的建模方法。其特点是充分考虑了预报系统中某些特殊预报因子突变点对预报关系的改变作用。数值实例表明，该模型在模拟和预报精度上比一般线性逐步回归模型有一定程度的提高。     

Defining the range of ecological shelter zones in the shore zone of Three Gorges Reservoir,China

To maintaining a health ecological environment in Three Gorges Reservoir (TGR) area, ecological shelter zones (ESZ) need to be built in the TGR shore zone urgently. Based on the implication and function of ESZ, this study first analyzed the relationships amongst three subsystems of the TGR area, including the upstream production-living land, the downstream reservoir water body, and the ESZ. Then a simple and practical hydrological environment model for controlling the eutrophication of the TGR water body was constructed to determine ESZ range of TGR. Additionally, based on the pollutant degradation efficiency of ESZ and the assimilative capacity of reservoir water body, a raster reverse tracking method was proposed to determine the range of ESZ. Thirdly, take Yangdu town in Zhongxian county as a typical region, the ESZ range under three scenarios of different rainfall intensity, degradation efficiency and inflow water quality that corresponding to the three decisive factors of defining ESZ range were discussed. Finally, the statistical laws of the ESZ’s width at each boundary points were discussed to facilitate the ESZ construction projects, and selected standardized rate at 70, 90, and 99 % were labelled as “General”, “Good” and “Excellent” level to represent the performance of the width of the ESZ range. In conclusion, it suggest “Good” level width as basic width of ESZ, and additionally a special protection zone should be put on upstream environment for the extreme large width at the boundary points.     

天津滨海地区浅层剪切波速与基底构造关系研究

Shear wave velocity is one of the important dynamic characteristics of soil layers and applied widely in aseismic engineering. In this paper, 500 drill logging data are used to make a linear interpolation based on 0.01°×0.01°×1m grid. A shallow 3-D shear wave velocity structure of Tianjin coastal area is obtained. According to the data and geological background, we selected two typical velocity profiles to try to introduce and explain its relationship to basement structure. The results show that the shear wave velocity structure clearly presents the characteristic of stratification and lateral inhomogeneity. Furthermore, the difference of the shear wave structure between tectonic elements is clear and the velocity structure between the two sides of the local or border fault in the Quaternary is disturbed or affected significantly. It intuitively shows that the basement structure and fault activity of this region had good control of sedimentation development and strata formation in the Quaternary period which would have an important effect on engineering seismic and geological condition evaluation.     

简谐荷载下单层球面网壳动力失效机理研究

以具有实际工程意义的40m跨度K8型单层球面网壳为研究对象,采用ANSYS程序的Pipe20单元,考察不同矢跨比网壳在不同频率的简谐荷载作用下,随着荷载幅值的逐渐增大,其宏观和微观响应的变化,详细阐述了2类破坏行为的规律,并通过一定规模的参数分析,给出单层球面网壳动力强度破坏判别准则.     

青藏高原东北缘北联池剖面清水营组孢粉组合特征及地质意义

青藏高原隆升是新生代最重要的地质事件之一,对邻区乃至全球的气候变化都产生了深远的影响,已有学者研究认为该期隆升与气候冷暖变化之间具有较好的耦合关系。北联池剖面在区域构造位置上隶属于青藏高原东北缘弧形构造带后缘六盘山以西,古近系清水营组主要为一套紫红色泥岩夹薄层石膏层为主的浅湖相沉积,蕴含了丰富的古环境和古气候信息。文章系统研究了剖面的孢粉组合特征,共鉴定出孢粉类型60属65种及若干未定种,其孢粉组合特征中被子植物花粉占绝对优势,裸子植物花粉和蕨类植物孢子含量很少。结合现有区域孢粉的研究成果,综合分析认为清水营组沉积的地质时代属于中晚渐新世—中新世早期。孢粉植物群以桦木科、胡桃科和榆科等落叶阔叶植物为主,组合中还出现了数量不多但种类繁多的热带—亚热带植物的花粉,而典型干旱的灌木和草本植物分子含量少,总体上反映了暖温带较温和湿润的古环境古气候背景。孢粉组合中几乎不见耐寒山地针叶植物花粉的出现,说明该时期区域气候环境尚未发生由暖转冷的重大变化,青藏高原向东北方向的隆升扩展尚未影响到六盘山地区。研究成果为约束青藏高原东北缘清水营组的沉积时代以及青藏高原隆升过程对区域古生态古气候的影响提供新的证据。     

兰坪白秧坪铜银多金属矿床成矿物质来源的铅和硫同位素示踪

白秧坪铜银多金属矿床主要产于白垩系下统景星组石英砂岩、粉砂岩中,矿石铅同位素组成特征与景星组砂岩的铅同位素组成比较接近,表明壳源物质参与了成矿作用。作ZartMan图解和Δγ-Δβ图解表明,矿石铅属于壳幔混合来源。矿石铅μ值介于9.43~9.65之间,Th/U比值介于3.72~3.87之间,表明矿石铅为壳幔混合铅。该矿床硫同位素组成表明,硫来源于深部地幔硫遭受地壳硫的混入。该矿床的成矿作用发生于开放体系之中,成矿物质来源为深部幔源物质混合了壳源物质。     

Tree-Ring δD as an Indicator of Asian Monsoon Intensity

Oxygen and hydrogen isotopic compositions of meteoric water are known to correlate with surface air temperature, except in tropical areas. This relationship has been described using a number of terms corresponding to specific observations, such as latitude, altitude and seasonal effects. However, these temperature effects do not seem to apply to precipitation in monsoonal areas of Asia. Questions have been raised as to whether the isotopic composition of meteoric water can be used to reconstruct paleomonsoon intensity. Tree rings of two modern spruce trees (Picea meyeri) and a 10,000-yr-old timber (Picea jezoensis) were analyzed for hydrogen isotopic composition. On average, the older tree is depleted in deuterium by 45‰ compared to the modern trees. We attribute this isotopic depletion to the strength of summer monsoons, which were more intense in the early Holocene than at present. Although this study is not definitive, it suggests that paleomonsoon intensity can be reconstructed by direct or proxy methods that yield the oxygen or hydrogen isotopic composition of meteoric water.     

Low-angle reflectivity modeling of land clutter

In this letter, a practical mean reflectivity model of radar land clutter (LC) for the complex system design of ground-based radars involved in low-angle targets on some typical terrains is studied using the inductive reasoning method. The functional relationships between the radar parameters and radar surface clutter backscattering are analyzed. Following the recent research work in the area of reflectivity modeling of LC in the literature, the least squares method is employed to estimate the model parameters. The model is validated using reliable practical data and shown to outperform other models in accuracy.