Characterization of the mechanical properties of a claystone by nano-indentation and homogenization

Based on the analyses of mineralogical compositions by X-ray diffraction and microstructure by optical microscopy, the Young’ modulus and hardness of a claystone were characterized by the nano-indentation technique and homogenization method. Three distinct microstructural zones are identified in the claystone: clay matrix, a composite matrix of clay and small mineral grains and imbedded quartz grains. The elastic modulus and hardness of different zones were determined by nano-indentation testing. Based on the statistical analysis of nano-indentation results, the spatial mappings and frequency distributions of elastic modulus and hardness of the different zones were obtained. The elastic moduli of main constituent phases of the claystone are then estimated from the nano-indentation tests. These values were further used for the determination of the macroscopic elastic modulus of the claystone using two different homogenization schemes: the dilute scheme and Mori–Tanaka scheme. The predicted values by the homogenization schemes are compared with experimental data obtained from conventional uniaxial compression tests.     

Evaluating climate change adaptation efforts on the US 50 states’ hazard mitigation plans

Climate change brings uncertain risks of climate-related natural hazards. The US Federal Emergency Management Agency (FEMA in Climate change: long-term trends and their implications for emergency management, 2011. https://www.fema.gov/pdf/about/programs/oppa/climate_change_paper.pdf) has issued a policy directive to integrate climate change adaptation actions into hazard mitigation programs, policies, and plans. However, to date there has been no comprehensive empirical study to examine the extent to which climate change issues are integrated into state hazard mitigation plans (SHMPs). This study develops 18 indicators to examine the extent of climate change considerations in the 50 SHMPs. The results demonstrate that these SHMPs treat climate change issues in an uneven fashion, with large variations present among the 50 states. The overall plan quality for climate change considerations was sustained at an intermediate level with regard to climate change-related awareness, analysis, and actions. The findings confirm that climate change concepts and historic extreme events have been well recognized by the majority of SHMPs. Even though they are not specific to climate change, mitigation and adaptation strategies that can help reduce climate change risks have been adopted in these plans. However, the plans still lack a detailed assessment of climate change and more incentives for collaboration strategies beyond working with emergency management agencies.     

Performance evaluation of ensemble learning techniques for landslide susceptibility mapping at the Jinping county,Southwest China

Natural Hazards - The objective of this study is to investigate different ensemble learning techniques namely Bagging, Boosting, and Stacking for LSM at the Jinping county, Southwest China. Two...     

冷空气引起的飞船主着陆场区偏北大风的特征分析及预报

分析了飞船主着陆场区1981—1999年1—4月和9—12月因冷空气而产生的偏北大风的过程中气候概况及其天气特征。通过分析发现:主着陆场区因冷空气引起的偏北大风以春季最频繁,秋、冬季最稀少;一天当中偏北大风以午后出现频率最大,午夜出现频率最少;对于不同季节的气压和温度,春、秋两季变化剧烈,冬季相对较小;在大风出现前24小时,主着陆场区的欧亚中高纬度大气环流以两槽一脊型、一槽一脊型、贝湖低压型为主;冷空气入侵前24小时,欧亚天气图上主着陆场区上游低层850hPa中高纬度有明显的冷中心,地面图场区上游冷高压中心的分布主要有3个区域:贝加尔湖西南至新疆、贝加尔湖到内蒙中北部、贝加尔湖西北部。大风前24小时在35～45°N、100～115°E等压线密集,等压线一般都在4根以上。     

Some phenomena of the interaction between vegetation and a atmosphere on multiple scales

This article studies the response of the distribution pattern and the physiological characteristics of the ecosystem to the spontaneous precipitation and the interaction between vegetation and the atmosphere on multiple scales in arid and semi-arid zones, based on measured data of the ecological physiological parameters in the Ordas Plateau of northern China. The results show that the vegetation biomass and the energy use efficiency of photosynthesis are especially sensitive to the annual precipitation; strong and complex interactions exist between the vegetation and the atmosphere on multiple scales leading to supernormal thermal heterogeneity of the underlying surface, the strong vortex movement and turbulence. This study can facilitate understanding of the land surface processes and the influences of global climate change as well as human activities on the human environment in the arid and semi-arid zones. It also aids in improving the parameterization schemes of turbulent fluxes of a heterogeneous underlying surface for land surface processes in climate models.     

Kinematic source model for simulation of near-fault ground motion field using explicit finite element method

1 Introduction The prediction of broadband near-fault ground motion is an important aspect of seismic risk analysis, and is essential for the evaluation of urban seismic safety. Many methodologies are used to model the near-fault ground motions, such as the Green function method, ?nite element (FE) / ?nite difference (FD) method and a hybrid method (Aagaard, 1999; Oprsal and Zahradnik, 2002; Oprsal et al., 2003 a and b). In the hybrid method, the FE / FD method is used to model the low fr…     

互联网影响下的“网剧”与传统“台剧”生产网络的结构差异

选取2016—2017年最具代表性的“网剧”和“台剧”各318部,运用社会网络分析法探讨互联网影响下的“网剧”与传统“台剧”生产网络的结构差异。研究表明：① 空间分布上看,相对于“台剧”生产网络,“网剧”生产网络中的企业区位、核心城市节点和城市间强联系更加集聚,尤其是向京津冀和长三角两大城市群集聚。② 网络结构上看,相对于“台剧”生产网络,“网剧”生产网络的规模小、联系数量少、分工粗略、中心势低,核心企业节点多为民营互联网影视企业,最强凝聚子群更为开放。最后,从互联网发展的地理格局、互联网带来的消费习惯改变、互联网引发的自由竞争,以及互联网视频平台企业的崛起四个方面分析了产生上述网络结构差异的原因。     

Dynamic characteristics of marine soft clay under variable phase difference and initial static shear stress

Abstract

Under seismic loading, the soil layer is subjected to multidirectional cyclic shear stress with different amplitudes and frequencies because of the coupling of multiple shear waves and the soil element within a slope or behind a retaining wall is subjected to initial static shear stress before subjected to cyclic loading. Due to the complexity of seismic loading propagation, a phase difference exists between the initial static shear stress and cyclic shear stress. To investigate the influence of the phase difference and initial static shear stress on cyclic shear strain, cyclic modulus, and cyclic strength, a series of laboratory tests are performed on Wenzhou marine soft clay by multi-directional simple shear system, which can simulate the actual state better by controlling the horizontal cyclic stress in the x and y directions simultaneously. As the phase difference varies from 0° to 90°, the dynamic shear modulus increases and cyclic strain accumulation decreases with an increasing number of cycles. The shear strain increases with the initial shear stress.     

Feasibility of Re-injecting the Production Effluent from Alkali–Surfactant–Polymer Flooding Systems Back into a Reservoir to Further Improve Oil Recovery

Natural Resources Research - Alkali–surfactant–polymer (ASP)-produced effluent contains polymer, alkali and surfactant, and it has higher content of suspended oil droplets and suspended...     

Effect of polysaccharide from Enteromorpha prolifera on maize seedlings under NaCl stress

In this study, a polysaccharide from Enteromorpha prolifera (EP) was extracted and its effect on maize seedlings under NaCl stress was investigated. Firstly, the components and structure of the EP were determined. We found that EP is a sulfated polysaccharide of high-molecular weight (Mw, 1 840 KDa) heteropolysaccharides and the main monosaccharide is rhamnose. The polysaccharide was applied to explore its effect on the growth of maize seedlings and its defense response under a salt stress. The results show that EP could promote the growth of maize seedlings under the salt stress. In addition, EP was shown able to significantly regulate membrane permeability and adjustment of osmotic substances such as soluble protein, soluble sugar, and proline, antioxidant enzymes containing superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase. Therefore, EP is an effective salt-resistant substance for the growth of maize seedlings under NaCl stress.