海风锋在渤海西岸局地暴雨过程中的作用

利用常规观测资料、地面加密自动站资料、多普勒雷达观测资料及中尺度TJ-WRF模式输出资料,对2009年7月6日天津宁河地区出现的暴雨天气过程进行了分析,重点分析了渤海湾海风锋对沿岸局地暴雨的触发机理。结果表明：此次局地暴雨过程是在有利天气背景条件下发生的,暴雨发生地存在局地层结不稳定和较好的水汽条件。海风锋本身有一辐合抬升区,区域内有弱对流存在;当海风锋移到局地存在层结不稳定且水汽充足的区域,其抬升区的辐合上升运动迅速加强,从而触发该地区雷暴的新生发展;海风锋与迎面移来的雷暴相遇,会对雷暴的加速发展起到加强作用。利用中尺度WRF模式输出资料进行分析看到,两条辐合线相交处易激发出强雷暴,雷暴出现在近地层大气暖干区的北端、湿空气的交汇处;海风锋对雷暴的新生发展有明显的触发抬升作用。     

Fluid–rock interaction in the Qitianling granite and associated tin deposits, South China: Evidence from boron and oxygen isotopes

The behavior of boron and its isotopes in fluid-dominant processes and hydrothermal alteration of granites is examined using fresh and altered granite samples from the Qitianling granite and associated hydrothermal tin deposits in South China. Boron concentrations are highest in the fresh granite (37 ppm) and depleted as a result of two stages of fluid mobility and fluid–rock interaction within the granite. Constraints provided both by δ¹¹B and δ¹⁸O data suggest that the first stage was related to exsolution of aqueous fluids from the granite magma at a temperature of > 450 °C. This was followed by further boron depletion in the granite by hydrothermal circulation of meteoric water at lower temperatures (~ 350 °C) and low water/rock ratios. The sensitivity of coupled boron and oxygen isotope systematics to these processes suggests that they can provide valuable constraints on of fluid mobility in granite and associated mineralization.     

基于BP人工神经网络的鹰潭市PM2.5和PM10浓度预测模型

利用2015—2019年鹰潭市5个大气成分监测站数据和气象站地面观测数据,运用主成分分析法,提取气象要素、气体污染物对PM2.5和PM10浓度影响的主要成分,调整BP人工神经网络的隐藏层个数和隐藏层节点数,构建基于BP人工神经网络的鹰潭市PM2.5和PM10浓度预测模型。结果表明：1） 气象要素中,共提取3个影响PM2.5、PM10浓度的主成分,分别为相对湿度、降水,气温、气压和风速,其中湿度、气温、风速与PM2.5、PM10浓度显著相关。2） 气体污染物中,共提取2个主成分,分别为SO2、NO2和O3,其中NO2、SO2与PM2.5、PM10浓度显著相关。3） 所建立的PM2.5、PM10浓度逐小时预测模型在20 h内预测性能良好,预测准确率分别为88%、86%,逐日预测模型在5 d内的预测性能良好,预测准确率分别为94%、92%,准确率较高,具有良好的预报性能。     

Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method

The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na_0.4Mg_0.6Al_1.6Si_0.4O₄ (40 % NaAlSiO₄–60 % MgAl₂O₄). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G ₀ = 121.960 ± 0.087 GPa and its pressure derivative G’ = 1.961 ± 0.009 for the NAL phase, and G ₀ = 129.653 ± 0.059 GPa and G’ = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa.     

Static and Dynamic Flexural Strength Anisotropy of Barre Granite

Granite exhibits anisotropy due to pre-existing microcracks under tectonic loadings; and the mechanical property anisotropy such as flexural/tensile strength is vital to many rock engineering applications. In this paper, Barre Granite is studied to understand the flexural strength anisotropy under a wide range of loading rates using newly proposed semi-circular bend tests. Static tests are conducted with a MTS hydraulic servo-control testing machine and dynamic tests with a split Hopkinson pressure bar (SHPB) system. Six samples groups are fabricated with respect to the three principle directions of Barre granite. Pulse shaping technique is used in all dynamic SHPB tests to facilitate dynamic stress equilibrium. Finite element method is utilized to build up equations calculating the flexural tensile strength. For samples in the same orientation group, a loading rate dependence of the flexural tensile strength is observed. The measured flexural tensile strength is higher than the tensile strength measured using Brazilian disc method at given loading rate and this scenario has been rationalized using a non-local failure theory. The flexural tensile strength anisotropy features obvious dependence on the loading rates, the higher the loading rate, the less the anisotropy and this phenomenon may be explained considering the interaction of the preferentially oriented microcracks.     

Agricultural drought risk analysis based on three main crops in prefecture-level cities in the monsoon region of east China

Drought, a frequent environmental disaster in the monsoon region of east China, significantly affects the agricultural economy. In recent years, researchers have emphasised drought risk management. This paper presents a preliminary method to analyse the risk of agricultural drought with regard to the loss of three main crops in individual prefecture-level cities in the monsoon region of east China. In this study, the agricultural drought risk is assessed by developing the index of consecutive rainless days and establishing loss rate curves based on the historical drought data from 1995 to 2008. The results show that the North China is seriously affected by drought hazard. Northeast China is the most sensitive to drought due to its large sown crop areas and weak irrigation. Approximately 11 % of the cities are in the extreme risk category; this category includes 26 % of the cultivated land area and 11 % of the total crop yields in the region. Twenty-three per cent of the cities, accounting for 28.5 % of the total cultivated land area and 26.4 % of the crop yields of the study area, are in high-risk areas, and 77 % of the cities with high and extreme risk levels are distributed in North and Northeast China. Moreover, 64 % of the cities in the monsoon region of East China are in moderate- and low-risk levels. These cities are primarily located south of the Yangtze River. In conclusion, minimising the risk of agricultural drought must be emphasised in northern China because of the high level of risk.     

WebGIS-based information management system for landslides triggered by Wenchuan earthquake

A digital landslide database has been created for Sichuan province, where a magnitude 8.0 earthquake at 2:28 p.m. on May 12, 2008, to provide the authorities and scientific communities with a tool for landslide risk assessment, emergency management, land-use planning, development of early warning system and enhancement of public awareness of natural hazards. Landslide data have been obtained from a variety of sources including technical reports and landslide inventory maps, and most of which were based on fieldwork and interpretation of aerial photographs. This paper presents the sources of landslide information, database design and the webGIS-based information management system. The database currently contains spatial information for about 9,000 landslides that were mostly triggered by the earthquake. Slide is the most common type of landslide in the database, but other types including rockfall and debris flow have also been identified. The website is an online GIS, providing access to comprehensive landslide information via the Internet. The development of the website allowed us to define the state of knowledge on landslide processes in Sichuan and to provide a preliminary identification of areas affected by landslides.     

Numerical simulation of flow processes in liquefied soils using a soil–water-coupled smoothed particle hydrodynamics method

Liquefaction can result in the damage or collapse of structures during an earthquake and can therefore be a great threat to life and property. Many site investigations of liquefaction disasters are needed to study the large-scale deformation and flow mechanisms of liquefied soils that can be used for performance assessments and infrastructure improvement. To overcome the disadvantages of traditional flow analysis methods for liquefied soils, a soil–water-coupled smoothed particle hydrodynamics (SPH) modeling method was developed to analyze flow in liquefied soils. In the proposed SPH method, water and soil were simulated as different layers, while permeability, porosity, and interaction forces could be combined to model water-saturated porous media. A simple shear test was simulated using the SPH method with an elastic model to verify its application to solid phase materials. Subsequently, the applicability of the proposed SPH modeling method to the simulation of interaction forces between water and soil was verified by a falling-head permeability test. The coupled SPH method produced good simulations for both the simple shear and falling-head permeability tests. Using a fit-for-purpose experimental apparatus, a physical flow model test of liquefied sand has been designed and conducted. To complement the physical test, a numerical simulation has been undertaken based on the soil–water-coupled SPH method. The numerical results correspond well with the physical model test results in observed configurations and velocity vectors. An embankment failure in northern Sweden was selected so that the application of the soil–water-coupled SPH method could be extended to an actual example of liquefaction. The coupled SPH method simulated the embankment failure with the site investigation well. They have also estimated horizontal displacements and velocities, which can be used to greatly improve the seismic safety of structures.     

白令海和西北冰洋表层沉积物磁化率特征初步研究

为了准确解释环境磁学参数记录的极地古气候环境变化信息,本研究对白令海和西北冰洋61个站位的表层沉积物进行了高、低频质量磁化率(χ)、非磁滞磁化率(χARM)和磁化率-温度(k-T)分析,以探明该区沉积物中磁性矿物的种类、来源与搬运路径。结果显示,样品的χ具有明显的地域分布特征。白令海的χ值整体高于楚科奇海,并在育空河口外侧和圣劳伦斯岛南侧较高,向北和向西南方向逐渐减小。楚科奇海中东部陆架上表层沉积χ值高于阿拉斯加沿岸,而西北冰洋深海平原和洋脊区的χ值最低。χARM的变化趋势与质量磁化率相似,但频率磁化率的变化趋势与质量磁化率正好相反。k-T分析结果显示阿留申海盆沉积物中的铁磁性矿物以磁赤铁矿占主导,白令海陆架育空河口外侧和圣劳伦斯岛南北两侧为磁铁矿,白令海陆架西部和楚科奇海陆架中东部为磁赤铁矿和磁铁矿,楚科奇海阿拉斯加沿岸为黄铁矿,而西北冰洋陆坡、深海平原和洋脊区为胶黄铁矿和黄铁矿,但高纬度区沉积物中的胶黄铁矿含量更高。沉积物中磁性矿物的区域性分布受沉积物来源、洋流和底质环境等因素的控制。白令海和楚科奇海陆架磁赤铁矿来源于亚洲大陆,白令海陆架东部的磁铁矿来自育空河流域,阿拉斯加沿岸沉积物中的黄铁矿,应为阿拉斯加西北部陆源侵蚀来源的或早期成岩作用形成的,西北冰洋深海盆区的胶黄铁矿,为自生成因的。