Loess magnetic properties in the Ili Basin and their correlation with the Chinese Loess Plateau

Over the past two decades, magnetoclimatological studies of loess-paleosol sequences in the Chinese Loess Plateau (CLP) have made outstanding achievements, which greatly promote the understanding of East Asian paleomonsoon evolution, inland aridification of Asia, and past global climate changes. Loess magnetic properties of the CLP have been well studied. In contrast, loess magnetic properties from outside the CLP in China have not been fully understood. We have little knowledge about the magnetic properties of loess in the Ili Basin, an intermontane depression of the Tianshan (or Tien Shan) Mountains. Here, we present the results of rock magnetic measurements of the Ili loess including mass magnetic susceptibility (χ) and anhysteretic remanent magnetization (ARM), high/low temperature dependence of susceptibility (TDS) and hysteresis, as well as X-ray diffraction (XRD) for mineral analysis. Based on the comparison with loess-paleosol sequences in the CLP (hereafter referred to as the Chinese loess), we discuss the possible magnetic susceptibility enhancement mechanism of the Ili loess. The results show that 1) the total magnetic mineral concentration of the Ili loess is far lower than that of the Chinese loess, though they have similar magnetic mineral compositions. The ferrimagnetic minerals in the Ili loess are magnetite and maghemite, and the antiferromagnetic mineral is hematite; XRD analysis also identifies the presence of ilmenite. The ratio of maghemite is lower in the Ili loess than in the Chinese loess, but the ratios of magnetite and hematite are higher in the Ili loess than in the Chinese loess. 2) The granularity of magnetic minerals in the Ili loess, dominated by pseudo-single domain (PSD) and multi-domain (MD) grains, is generally much coarser than that of the Chinese loess. Ultrafine pedogenically-produced magnetic grains have a very limited contribution to the susceptibility enhancement. Rather, PSD and MD particles of magnetite and maghemite are the main contributors to the enhancement of susceptibility in the Ili loess. 3) The susceptibility enhancement mechanism for the Ili loess is complicated and superimposes both a wind velocity/vigor model (Alaskan or Siberian model) and the in situ ultrafine grain pedogenic model; the former might play an important role in the Ili loess. 4) Magnetic susceptibility enhancements of the Ili loess are related not only to the eolian input of the source area, but also to the local climate, landform, and geological background. Therefore, great care should be taken when reconstructing paleoclimate using magnetic susceptibility data from the Ili loess.     

Prediction criteria for groundwater potential zones in Kemuning District,Indonesia using the integration of geoelectrical and physical parameters

The presence of groundwater is strongly related to its geological and geohydrological conditions.It is,however,important to study the groundwater potential in an area before it is utilized to provide clean water.Werner-Schlumberger’s method was used to analyze the groundwater potential while hydraulic properties such as soil porosity and hydraulic conductivity were used to determine the quality and ability of the soil to allow water’s movement in the aquifer.The results show that the aquifer in the Sekara and Kemuning Muda is at a depth of more than 6 meters below the ground level with moderate groundwater potential.It is also found that the aquifer at depths of over 60 m have high groundwater potential.Moreover,soil porosity in Kemuning is found to be average while the ability to conduct water was moderate.This makes it possible for some surface water to seep into the soil while the remaining flows to the rivers and ditches.     

大跨度主-副桁架钢结构的地震反应探讨分析

桁架钢结构被广泛应用于大跨度建筑中,分析桁架钢结构的地震反应具有一定的现实意义。构建大跨度主-副桁架钢结构的有限元模型,以该模型作为研究对象,对其进行地震反应的探讨分析。采用自振特性分析方法在刚度和质量两个因素的基础上分析大跨度主-副桁架钢结构的自振特性;通过振型分解反应谱法分析大跨度主-副桁架钢结构的力学性能,利用桁架钢结构的力学性能分析其地震作用下的反应。模拟发现,大跨度主-副桁架钢结构刚度较好,其抗风柱柱脚连接处的受力最强且位移最大,为大跨度主-副桁架钢结构的地震反应研究提供参考,为其抗震设计提供初步依据。     

一种改进的软土结构性弹塑性损伤模型

提出了一个改进的土结构性弹塑性损伤模型。该模型引入修正剑桥模型的屈服函数来描述损伤土特性,并建议了新的损伤演化规律。由于剑桥模型本身建立在大量重塑土试验的基础上,故能较精确地描述完全损伤土的特性;此外,其参数有较为完善的测定方法,且积累了丰富的经验值。该改进的模型能较好地应用于工程实践,并易于推广。     

Application of 3-D Geoscience Modeling Technology for the Estimation of Solid Mineral Reserves

Abstract: Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology (3-D GMT), this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT: building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves.     

昆中断裂带南北陆块基底、盖层沉积、岩浆岩对比研究——昆中断裂带构造意义的讨论

本文依据1∶25万区域地质调查成果资料,从昆中断裂带对南北两侧的基底变质岩系(包括变基性火山岩、变泥质岩)、表壳盖层沉积岩系、前寒武纪长英质火成侵入岩以及镁铁-超镁铁质侵入岩的沉积建造、岩石类型组合、岩石地球化学及所反映的源岩物性的控制,系统对比讨论了昆中断裂带南北两侧基底陆块特征及昆中断裂带的构造属性。得出以昆中断裂带为界,南北两侧陆块的大陆岩石圈,无论在表壳沉积岩系、中-下地壳和地幔的层性和物性结构及地球化学成分都存在显著差异。从而提出昆仑造山带实际上是个两陆块碰撞复合陆缘造山带。在元古宇以前南北陆块并非属同一古陆块,或者说昆中断裂带为欧亚大陆和冈瓦纳大陆的真正分界或二者的拼合带。     

静压预制桩工程性状研究──以河南某电厂技改工程为例

以河南某电厂技改工程为例 ,根据现场检测结果 ,探讨了影响静压预制桩沉桩深度成因 ,分析了静压桩承载力的分布规律。研究结果证明静压桩的沉桩深度和承载力与地基土的性状密切相关。对于河南某电厂技改工程场地 ,尽管桩端进入砂较小深度 ,却可以在桩端平面附近良好土层的作用下提供较大的端阻力。     

Recursive evaluation of interaction forces and property matrices from unit-impulse response functions of unbounded medium based on balancing approximation

Starting from the unit-impulse response matrix of the unbounded medium, a discrete-time formulation permitting the recursive evaluation of the interaction forces and a continuous-time formulation yielding property matrices corresponding to a model with a finite number of degrees of freedom are discussed. This is achieved using the balancing approximation method which is easily automated, guarantees stability and leads to highly accurate results. © 1998 John Wiley & Sons Ltd.     

松辽盆地丰乐地区营城组火山岩储层预测

徐家围子断陷的主要产气层段为营城组火山岩段地层,所以研究该地层对寻找天然气藏具有非常重要的意义.本文利用丰乐地区的高分辨率地震资料、岩石物性资料、测井资料对下白垩统营城组火山岩进行构造精细解释,火山岩地震相及岩相分析从而进行储层预测,利用均方根振幅、瞬时频率能量及瞬时吸收系数能量等地震属性分析结合地震反演技术精细刻画火山岩储层.结果认为：均方根振幅、瞬时频率能量和瞬时吸收系数能量能较好预测火山岩相和储层物性;有利储层在反演剖面上表现为中低阻抗特征,中等密度;较好储层主要分布在工区的西部与中部.     

Landowner Attitudes Toward Conservation Easements: Balancing the Private and Public Interest in Land

Private land conservation provides an opportunity to address problems of habitat fragmentation and biodiversity loss caused by an increase in the development and parcelization of private land. Conservation easements (CEs) are used to protect significant natural qualities of private land. In this study, we explore landowner attitudes toward CEs through the implementation of a mixed-mode survey to private landowners in the Whychus Creek Watershed (Deschutes County, Oregon). The results of an exploratory factor analysis suggest there are two dimensions to landowner attitudes toward CEs, an internal dimension and an external dimension. We found that positive external attitudes are primarily influenced by environmental beliefs, whereas positive internal attitudes are influenced by a suite of factors, including financial beliefs and perceived risk to private ownership. Awareness of CEs may also play a role in attitude development. Through this research, we argue that CEs may be beneficial in reintegrating the public good into private property.