Refined modeling and movement characteristics analyses of irregularly shaped particles

Irregularly shaped (IRS) particles widely exist in many engineering and industrial fields. The macro physical and mechanical properties of the particle system are governed by the interaction between the particles in the system. The interaction between IRS particles is more complicated because of their complex geometric shape with extremely irregular and co‐existed concave and convex surfaces. These particles may interlock each other, making the sliding and friction of IRS particles more complex than that of particles with regular shape. In order to study the interaction of IRS particles more efficiently, a refined method of constructing discrete element model based on computed tomography scanning of IRS particles is proposed. Three parameters were introduced to control the accuracy and the number of packing spheres. Subsequently, the inertia tensor of the IRS particle model was optimized. Finally, laboratory and numerical open bottom cylinder tests were carried out to verify the refined modeling method. The influence of particle shape, particle position, and mesoscopic friction coefficient on the interaction of particles was also simulated. It is noteworthy that with the increase of mesoscopic friction coefficient, the fluidity of IRS particle assembly decreases, and intermittent limit equilibrium state may appear. Copyright © 2014 John Wiley & Sons, Ltd.     

Chemical weathering and CO2 consumption in the glaciated Karuxung River catchment,Tibetan Plateau

Climate factors play critical roles in controlling chemical weathering, while chemically weathered surface material can regulate climate change. To estimate global chemical weathering fluxes and CO₂ balance, it is important to identify the characteristics and driving factors of chemical weathering and CO₂ consumption on the Tibetan Plateau, especially in glaciated catchments. The analysis of the hydro-geochemical data indicated that silicate weathering in this area was inhibited by low temperatures, while carbonate weathering was promoted by the abundant clastic rocks with fresh surfaces produced by glacial action. Carbonate weathering dominated the riverine solute generation (with a contribution of 58%, 51%, and 43% at the QiangYong Glacier (QYG), the WengGuo Hydrological Station (WGHS), and the lake estuary (LE), respectively). The oxidation of pyrite contributed to 35%, 42%, and 30% of the riverine solutes, while silicate weathering contributed to 5%, 6%, and 26% of the riverine solutes at the QYG, WGHS, and LE, respectively. The alluvial deposit of easily weathering fine silicate minerals, the higher air temperature, plant density, and soil thickness at the downstream LE in comparison to upstream and midstream may lead to longer contact time between pore water and mineral materials, thus enhancing the silicate weathering. Because of the involvement of sulfuric acid produced by the oxidation of pyrite, carbonate weathering in the upstream and midstream did not consume atmospheric CO₂, resulting in the high rate of carbonate weathering (73.9 and 75.6 t km⁻² yr⁻¹, respectively, in maximum) and potential net release of CO₂ (with an upper constraint of 35.6 and 35.2 t km⁻² yr⁻¹, respectively) at the QYG and WGHS. The above results indicate the potential of the glaciated area of the Tibetan Plateau with pyrite deposits being a substantial natural carbon source, which deserves further investigation.     

Efficient estimation of flood forecast prediction intervals via single‐ and multi‐objective versions of the LUBE method

Prediction intervals (PIs) are commonly used to quantify the accuracy and precision of a forecast. However, traditional ways to construct PIs typically require strong assumptions about data distribution and involve a large computational burden. Here, we improve upon the recent proposed Lower Upper Bound Estimation method and extend it to a multi‐objective framework. The proposed methods are demonstrated using a real‐world flood forecasting case study for the upper Yangtze River Watershed. Results indicate that the proposed methods are able to efficiently construct appropriate PIs, while outperforming other methods including the widely used Generalized Likelihood Uncertainty Estimation approach. Copyright © 2016 John Wiley & Sons, Ltd.     

台湾海峡西岸海雾研究现状与未来发展方向

台湾海峡是一个海雾多发的交通要道,海雾灾害往往会导致人员和财产损失。对当前有关的海雾研究现状进行总结,以海峡西岸为代表,比较台湾海峡海雾和其他海域的大雾研究进展状况,主要包括海雾发生时的天气气候学特征、监测手段、微物理特征研究和海雾数值预报研究等。结果表明,台湾海峡西岸在天气气候学方面已经取得了一定的成果;监测手段随着科学技术的发展,也不断的完善,但在如何对卫星遥感监测结果进行反演方面还需进一步研究;海雾的微物理特征研究有助于海雾模式的改进和卫星遥感海雾反演技术的提高,但台湾海峡西岸尚未开始研究,是下一步的研究重点;台湾海峡海雾数值模拟工作较少,伴随观测技术的不断进步、动力统计方法的不断完善,可通过数值预报产品与传统的天气学方法相结合,提高台湾海峡海雾预报水平。     

淤泥质海岸入海河口闸下港道河相关系

以江苏沿海北部的射阳河闸下港道为原型,建立二维水动力及泥沙输运概化数学模型,模拟了淤泥质海岸闸下港道淤积过程。分别在不考虑径流年内分配变化和考虑径流年内分配变化的情况下,研究了入海径流对港道内水沙动力和冲淤演变的影响。参考前人研究成果,结合量纲和谐准则,根据模型的计算结果,建立了淤泥质海岸闸下港道年均平衡流量与汛期排水比例、河床断面积、外海潮差、潮波变形、港道长度等因素间的河相关系式,对在实际情况中达到动态冲淤平衡的某条特定港道,可简化为港道年均流量与河床断面积间关系式的简化形式,并通过分析实测资料,对公式的简化形式加以佐证。     

深海嗜热异化铁还原菌Caloranaerobacter ferrireducens DY22619T对不同铁氧化物的铁还原特性

异化铁还原微生物在铁元素的地球化学循环中具有重要意义。深海热液活动是大洋铁元素的重要来源,目前深海热液环境中铁代谢相关微生物研究很少。本文对一株分离自深海热液区的嗜热异化铁还原菌新种Caloranaerobacter ferrireducens DY22619T的铁还原特性进行分析,比较了该菌对无定形羟基氧化铁、无定形铁氧化物和针铁矿3种不同铁氧化物的铁还原速率;并利用透射电镜对矿化产物进行矿物形貌、组成元素和晶型的分析。研究发现该菌生长在指数期至稳定期时,铁还原速率最快,其中对无定形羟基氧化铁和无定形铁氧化物的还原速率较高,达2.82 μmol/h和2.15 μmol/h;透射电镜结果表明,该菌可将3种不同胞外铁氧化物均还原矿化形成颗粒状磁铁矿,由针铁矿矿化形成的磁铁矿少但粒径最大,而由无定形铁氧化物形成的磁铁矿晶面不同于另外两种铁氧化物。结果表明,该菌有很强的铁还原和矿化能力,能厌氧呼吸还原三价铁氧化物,但是铁氧化物的性质对该菌胞外铁还原能力和矿化形成的磁铁矿的性质有重要影响。本研究为认识深海热液环境中异化铁还原菌在铁元素的地球化学循环和生物成矿过程提供了参考。     

Hydrothermal Fluid Sources of the Fengjia Barite–fluorite Deposit in Southeast Sichuan,China: Evidence from Fluid Inclusions and Hydrogen and Oxygen Isotopes

The Fengjia barite–fluorite deposit in southeast Sichuan is a stratabound ore deposit which occurs mainly in Lower Ordovician carbonate rocks. Here we present results from fluid inclusion and oxygen and hydrogen isotope studies to determine the nature and origin of the hydrothermal fluids that generated the deposit. The temperature of the ore‐forming fluid shows a range of 86 to 302 °C. Our detailed microthermometric data show that the temperature during mineralization of the fluorite and barite in the early ore‐forming stage was higher than that during the formation of the calcite in the late ore‐forming stage. The salinity varied substantially from 0.18% to 21.19% NaCl eqv., whereas the density was around 1.00 g/cm³. The fluid composition was mainly H₂O (>91.33%), followed by CO₂, CH₄ and traces of C₂H₆, CO, Ar, and H₂S. The dominant cation was Na⁺ and the dominant anion Cl^‐, followed by Ca²⁺, SO₄^2‐, K⁺, and Mg²⁺, indicating a mid–low‐temperature, mid‐low‐salinity, low‐density NaCl–H₂O system. Our results demonstrate that the temperature decreased during the ore‐forming process and the fluid system changed from a closed reducing environment to an open oxidizing environment. The hydrogen and oxygen isotope data demonstrate that the hydrothermal fluids in the study area had multiple sources, primarily formation water, as well as meteoric water and metamorphic water. Combined with the geological setting and mineralization features we infer that the stratabound barite–fluorite deposits originated from mid–low‐temperature hydrothermal fluids and formed vein filling in the fault zone.