1730年夏季黄淮地区暴雨极端事件研究

1730年（清雍正八年）7—8月,我国黄淮地区连续暴雨17 d,引起黄河、大运河和淮河暴涨、决堤的大范围洪涝灾害。这是小冰期中相对温暖时段气候背景下的极端气候事件。本文依据历史文献记载复原了1730年夏季暴雨时段的天气实况,绘制了暴雨区域图显示强降雨中心移动动态和水灾地域分布图,概述当年气候特点,指出暴雨事件与台风活动的关联。1730年是太阳活动周极小年的前3年、有重大火山活动,是极强的厄尔尼诺事件后的第2年。这些天气特点和背景条件与现代罕见的1975年河南“75?8暴雨”相似。     

Position variations of the polarization jet and injection boundary of energetic ions during substorms

The comparison of selected cases of polarization jet observation at ground stations and measurements of energetic ions at the AMPTE/CCE satellite shows that these phenomena occur simultaneously and on the same L shells. Polarization jet observations at DMSP satellites make it possible to statistically determine the dependence of its equatorial boundary position on the AE-index value. It is also shown that, in the case of isolated magnetic disturbances, the position of the inner boundary of injection of energetic ions measured at the AMPTE/CCE satellite depends on the AE index. It was found that the dependences of both boundaries on the AE index match over a wide range of AE variations. This is evidence that the equatorial boundary polarization jet band and the inner boundary of the injection of energetic ions are physically interconnected and are formed on the same L shells during substorms.     

Effect of pore geometry on Gassmann fluid substitution

Although there is no assumption of pore geometry in derivation of Gassmann's equation, the pore geometry is in close relation with hygroscopic water content and pore fluid communication between the micropores and the macropores. The hygroscopic water content in common reservoir rocks is small, and its effect on elastic properties is ignored in the Gassmann theory. However, the volume of hygroscopic water can be significant in shaly rocks or rocks made of fine particles; therefore, its effect on the elastic properties may be important. If the pore fluids in microspores cannot reach pressure equilibrium with the macropore system, assumption of the Gassmann theory is violated. Therefore, due to pore structure complexity, there may be a significant part of the pore fluids that do not satisfy the assumption of the Gassmann theory. We recommend that this part of pore fluids be accounted for within the solid rock frame and effective porosity be used in Gassmann's equation for fluid substitution. Integrated study of ultrasonic laboratory measurement data, petrographic data, mercury injection capillary pressure data, and nuclear magnetic resonance T₂ data confirms rationality of using effective porosity for Gassmann fluid substitution. The effective porosity for Gassmann's equation should be frequency dependent. Knowing the pore geometry, if an empirical correlation between frequency and the threshold pore‐throat radius or nuclear magnetic resonance T₂ could be set up, Gassmann's equation can be applicable to data measured at different frequencies. Without information of the pore geometry, the irreducible water saturation can be used to estimate the effective porosity.     

Problem of transient turbulent convection and a semiempirical profile of turbulent heat exchange coefficient in freshwater bodies

A problem of convective cooling of both freshwater and saltwater lake is formulated. A transient one-dimensional turbulent model with variable layer depth is proposed to describe the process of freezing. The dependence of layer depth on time is determined by a universal equation describing the propagation of Deardorff convective layer. A combination of the main form of equations of Kolmogorov–Obukhov theory and available experimental data is shown to allow the construction of a universal profile of turbulent exchange coefficient, depending on the height.     

Seismic performance of masonry walls retrofitted with steel reinforced grout

An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd.     

The intensity of landslide and mudflow processes in the Greater Sochi area and its variation in the early XXI century

Data on landslide and mudflow manifestations in the Greater Sochi and Krasnaya Polyana areas in recent years are analyzed. Changes in their activity under natural and technogenic effects during the preparation to the 2014 Winter Olympics are taken into account. The specific features of the intensification of these processes in 2012–2013 are identified.     

State of heterotrophic bacterioplankton of Yenisei estuary and the zone of Ob–Yenisei discharge in autumn in relation with environmental factors

In September 2011, variations of the total abundance of bacteria were studied, including, for the first time, the abundance of bacteria with intact membranes and active electron transport chains, as well as chlorophyll a concentrations and some hydrological and hydrochemical characteristics of water in Yenisei estuary and the zone of Ob–Yenisei river discharge. The study found abundant, viable, and actively functioning bacterioplankton to exist in the region. The absolute values of all microbiological characteristics were found to decrease with the distance from the freshened waters of Yenisei estuary toward the seawater of the Ob–Yenisei river discharge, while the percentage of bacteria with intact membranes and actively functioning microorganisms in bacterioplankton increased in the same direction. Positive correlations were found to exist between the values of all examined microbiological characteristics and the concentration in water of chlorophyll a, silicium, organic nitrogen, and oxygen, as well as water temperature. The same biological characteristics showed negative correlations with water salinity and phosphates. The spatial distribution of bacteria in the examined water body was supposed to be due mostly to the intensity of hydrodynamic processes, rather than the biogenic matter content of water.     

Low‐Resolution Modeling of Dense Drainage Networks in Confining Layers

Groundwater‐surface water (GW‐SW) interaction in numerical groundwater flow models is generally simulated using a Cauchy boundary condition, which relates the flow between the surface water and the groundwater to the product of the head difference between the node and the surface water level, and a coefficient, often referred to as the “conductance.” Previous studies have shown that in models with a low grid resolution, the resistance to GW‐SW interaction below the surface water bed should often be accounted for in the parameterization of the conductance, in addition to the resistance across the surface water bed. Three conductance expressions that take this resistance into account were investigated: two that were presented by Mehl and Hill (2010) and the one that was presented by De Lange (1999). Their accuracy in low‐resolution models regarding salt and water fluxes to a dense drainage network in a confined aquifer system was determined. For a wide range of hydrogeological conditions, the influence of (1) variable groundwater density; (2) vertical grid discretization; and (3) simulation of both ditches and tile drains in a single model cell was investigated. The results indicate that the conductance expression of De Lange (1999) should be used in similar hydrogeological conditions as considered in this paper, as it is better taking into account the resistance to flow below the surface water bed. For the cases that were considered, the influence of variable groundwater density and vertical grid discretization on the accuracy of the conductance expression of De Lange (1999) is small.