Numerical Simulation of the Rock SHPB Test with a Special Shape Striker Based on the Discrete Element Method

A split Hopkinson pressure bar (SHPB) system with a special shape striker has been suggested as the test method by the International Society for Rock Mechanics (ISRM) to determine the dynamic characteristics of rock materials. In order to further verify this testing technique and microscopically reveal the dynamic responses of specimens in SHPB tests, a numerical SHPB test system was established based on particle flow code (PFC). Numerical dynamic tests under different impact velocities were conducted. Investigation of the stresses at the ends of a specimen showed that the specimen could reach stress equilibrium after several wave reverberations, and this balance could be maintained well for a certain time period after the peak stress. In addition, analyses of the reflected waves showed that there was a clear relationship between the variation of the reflected wave and the stress equilibrium state in the specimen, and the turning point of the reflected wave corresponded well with the peak stress in the specimen. Furthermore, the reflected waves can be classified into three types according to their patterns. Under certain impact velocities, the specimen deforms at a constant strain rate during the whole loading process. Finally, the influence of the micro-strength ratio ( \({{\tau_{\text{c}} } \mathord{\left/ {\vphantom {{\tau_{\text{c}} } {\sigma_{\text{c}} }}} \right. \kern-0pt} {\sigma_{\text{c}} }}\) ) and distribution pattern on the dynamic increase factor (DIF) of the strength DIF were studied, and the lateral inertia confinement and heterogeneity were found to be two important factors causing the strain rate effect for rock materials.     

Research on the inversion of elemental abundances from Chang’E-2 X-ray spectrometry data

The elemental abundances of lunar surface are the important clues to study the formation and evolution history of the Moon. In 2010, China＇s Chang＇E-2 （CE-2） lunar orbiter carried a set of X-ray spectrometer （XRS） to investigate the elemental abundances of the lunar surface. During CE-2＇s life span around the Moon, the XRS ex- perienced several events of solar flare. The X-ray solar monitor onboard recorded the spectra of solar X-rays at the same time. In this paper, we introduced the XRS instrument and data product. We analyzed the characteristics of the XRS data. Using the data obtained during an M solar flare event which had occurred on Feb. 16, 201 l, we derived the elemental abundances ofMg, A1, Si, Ca and Fe of the lunar surface in the Oceanus Procellarum. Finally, we dis- cussed the factors that influence the accuracy of the inversion.     

断层模型约束反演在煤层横向预测中的应用研究

在精细断层解释的基础上,以地震层位为趋势面,通过对趋势面局部微调,使各层面的变化趋势和空间关系更加合理。通过网格精度和地层厚度有控制构建包含断层在内的精细构造框架模型,并根据波阻抗的差异特征,利用断层模型约束波阻抗反演实现煤层的横向预测。实例表明,基于断层模型约束反演技术的煤层横向预测方法,可精细描述煤层尖灭、变薄、分叉合并、厚度变化等赋煤形态,经实际钻井资料验证吻合较好。     

Phytoremediation of cadmium using plant species of Athyrium wardii (Hook.)

Athyrium wardii (Hook.) is a promising herbaceous plant species for phytostabilization of cadmium (Cd)-contaminated sites with large biomass and fast growth rate. However, little information is available on its tolerance mechanisms toward Cd. To further understand the mechanisms involved in Cd migration, accumulation and detoxification, the present study investigated subcellular distribution and chemical forms of Cd in the mining ecotypes and corresponding non-mining ecotypes of A. wardii via greenhouse pot experiment. Subcellular fractionation of Cd-containing tissues demonstrated that the majority of the element was mainly located in soluble fraction in cell walls. This indicated that both the vacuoles and cell walls might be evolved the Cd tolerance mechanisms to protect metabolically active cellular compartments from toxic Cd concentrations. Meanwhile, Cd taken up by the plant existed in different chemical forms. Results showed that the majority of Cd in plant was in undissolved Cd–phosphate complexes (extracted by 2 % CH₃COOH), followed by water-soluble Cd–organic acid complexes, Cd(H₂PO₄)₂, pectates and protein form (extracted by deionized water and 1 M NaCl), whereas only small amount of Cd in roots was in inorganic form (extracted by 80 % ethanol), which suggests low capacity to be transported to aboveground tissues. It could be suggested that Cd integrated with undissolved Cd–phosphate complexes in cell wall or compartmentalization in vacuole might be responsible for the adaptation of the mining ecotypes of A. wardii to Cd stress.     

Identification of fracture development period and stress field analysis based on fracture fabrics in tectonic superposition areas

As a direct consequence of multiple periods of stress applied on areas with tectonic superposition, the multiple-periods fractures have complex abutting relationships, and the field study of fractures is usually restricted by outcrop conditions, such as section direction. Therefore, previous studies of superposed stress fields based on fractures have been generally performed in areas with proper observation conditions and clear abutting relationships. In contrast, in many other areas, the identification of fracture development period based on field observation is often infeasible. Compared to abutting relationships, fracture fabrics obtained from field measurement are not affected by the restriction of outcrops and consequently are more representative of the fractures. According to the analysis of fracture fabrics and fracture features, this paper has separated and extracted the superposed fracture sets and identified the fracture development period in the area without available abutting relationships. Taking the southern segment of the Longmen Mountain thrust belt as an example, fractures of two development periods are identified and timed in the tectonic superposition area between two adjacent fold belts. The analysis of stress direction in each period suggests that the structural boundaries, consisting of such pre-existing structures as faults and anticlines, could have induced directional rotation in the subsequent stress. An equivalent result was achieved using a finite element simulation of the stress field. Based on the stress analysis of the field sites and the stress field simulation, the stress variation in the tectonic superposition area is well modeled.     

地理学史教学行动研究与教师专业成长--以“地球的形状”为例

地理学史具有独特的教育价值,是地理教学改革关注的重点议题之一,但其在实践中却存在“高价值低应用”的困境。本文以H教师的地理学史教学行动研究为例,呈现了地理学史教学的具体实践过程,探讨了地理学史教学对学生理解学科本质与培养其核心素养带来的效果,阐述了地理学史教学对教师专业成长带来的积极影响,旨在促进地理学史教学真正走进现实课堂。     

Vegetation-related dry deposition of global PM2.5 from satellite observations

Journal of Geographical Sciences - Vegetation plays an important role in the dry deposition of particles with significant spatial variability, but the magnitude remains unclear at the global scale....     

山西省石炭纪铝土矿中鲕特征及成因

在重新划分山西省石炭纪铝土矿中鲕的类型基础之上,详细总结了各种类型鲕的循环,并结合石炭纪铝土矿的成矿古环境,深入探讨了鲕的形成过程,明确提出了组成鲕的物质组分之颗粒细微,粘附能力强与炎热多雨的气候环境是铝土矿中鲕形成的主要因素。     

榆木山东麓断裂带晚第四纪活动特征的初步研究

位于甘肃河西走廊中部、张掖——民乐盆地西侧的榆木山东麓断裂带,是一条走向北北西向晚第四纪活动断裂。根据断层地貌特征研究,断裂带显示为一高角度右旋挤压的活动特点。全新世以来,该断裂带的平均滑移速率为:水平位错1.93毫米/年,垂直位错0.82毫米/年。     

Effects of the external carbon sources on the microbes in the simultaneous biological removal of SO2 and NO x process

Effects of sodium acetate and glucose on the microbes from the simultaneous flue gas desulfurization and denitrogenation tandem biotrickling process were respectively investigated. For the acidophiles, although the impacts of the carbon sources on the total microbial growth and nitrogen conversion in the medium were slight, the sulfite oxidation rate was obviously improved. The highest sulfite ion oxidation ratio in 48 h was up to 47.2 % as 258.08 mmol L^?1 sodium acetate was added in the medium. For the neutrophiles, the two carbons promoted the total microbial growth, but only sodium acetate could enhance the nitrite consumption significantly. The best nitrite consumption rate in 48 h could reach to 86.7 % with 258.08 mmol L^?1 sodium acetate. It provides valuable information for the development of biological SO₂ and NO _x simultaneous purification process.