嘉山地震台大地电场资料真实性分析

分析嘉山地震台自2007年运行以来的大地电场观测资料,并对数据的变化特征进行研究,总结分析部分干扰引起的电场变化的曲线特征,给出不同影响因素导致的曲线异常变化情况,为大地电场干扰排除提供依据.     

A study on the seismic performance of steel‐reinforced concrete frame‐concrete core wall high‐rise mixed structure by large‐scale shaking table tests and numerical simulations

This paper reports a study for the seismic performance of one large‐scaled (1/15) model of 30‐story steel‐reinforced concrete frame‐concrete core wall mixed structure. The study was implemented by both shaking table tests, in which the similarity ratio for lateral and gravitational accelerations was kept to 1:1, and numerical nonlinear dynamic analysis. The test observations presented herein include story displacement, interstory drift, natural vibration periods, and final failure mode. The numerical analysis was performed to simulate the shaking table test procedure, and the numerically obtained responses were verified by the test results. On the basis of the numerical results, the progressions of structural stiffness, base shear, and overturning moment were investigated, and the distributions of base shear and overturning moment between frame and core wall were also discussed. The test demonstrates the seismic performance of the steel‐reinforced concrete frame‐core wall mixed structure and reveals the potential overturning failure mode for high rise structures. The nonlinear analysis results indicate that the peripheral frames could take more shear forces after core wall damaged under severe earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.     

有明黏土中搅拌桩施工时的孔隙水压力

深层搅拌桩施工时,固化剂的注入与叶片的搅拌作用不可避免地会扰动周围土体,改变桩周土体中的应力状态,产生超静孔隙水压力。在高灵敏性的日本有明黏土中搅拌桩施工时对周围土体中的孔隙水压力进行了现场监测。监测结果表明周围土体中产生了很高的超静孔隙水压力,其量值较土体的初始上覆压力还要大,使土体中的有效应力为零,处于张拉状态,但是该超静孔隙水压力在初始阶段消散得非常快。为分析施工引起的超静孔隙水压力,将搅拌桩施工时和周围土体的相互作用采用受剪的孔穴扩张过程来模拟,提出一种简单的方法来计算搅拌桩施工时周围土体中的超静孔隙水压力,同时考虑了固化剂注入时的膨胀压力与旋转叶片在搅拌时所产生的剪切力的作用。超静孔隙水压力由土的不排水抗剪强度、剪切力、注浆压力和孔隙压力系数所确定。所提出的计算方法得到实测数据的验证。     

Height prediction of water flowing fractured zones based on BP artificial neural network

Factures caused by deformation and destruction of bedrocks over coal seams can easily lead to water flooding(inrush)in mines,a threat to safety production.Fractures with high hydraulic conductivity are good watercourses as well as passages for inrush in mines and tunnels.An accurate height prediction of water flowing fractured zones is a key issue in today's mine water prevention and control.The theory of leveraging BP artificial neural network in height prediction of water flowing fractured zones is analysed and applied in Qianjiaying Mine as an example in this paper.Per the comparison with traditional calculation results,the BP artificial neural network better reflects the geological conditions of the research mine areas and produces more objective,accurate and reasonable results,which can be applied to predict the height of water flowing fractured zones.     

Three dimensional numerical simulation of residential building on shrink–swell soils in response to climatic conditions

Shrink–swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil–foundation–building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro‐mechanical stress analysis is used to simulate the volume change of shrink–swell soils due to both mechanical stress and water content variations. Coupled hydro‐mechanical stress‐jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2‐year period is presented. Finally, a three‐dimensional simulation is made for a virtual residential building on shrink–swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd.     

Automatic morphological classification of galaxy images

We describe an image analysis supervised learning algorithm that can automatically classify galaxy images. The algorithm is first trained using manually classified images of elliptical, spiral and edge-on galaxies. A large set of image features is extracted from each image, and the most informative features are selected using Fisher scores. Test images can then be classified using a simple Weighted Nearest Neighbour rule such that the Fisher scores are used as the feature weights. Experimental results show that galaxy images from Galaxy Zoo can be classified automatically to spiral, elliptical and edge-on galaxies with an accuracy of ∼90 per cent compared to classifications carried out by the author. Full compilable source code of the algorithm is available for free download, and its general-purpose nature makes it suitable for other uses that involve automatic image analysis of celestial objects.     

Water quality in a polluted lowland stream with chronically depressed dissolved oxygen: Causes and effects

Abstract

The Whangamaire Stream (North Island, New Zealand) has high concentrations of nitrate nitrogen (NO^? ₃‐N), biochemical oxygen demand (BOD₅), and Kjeldahl nitrogen (TKN) as a result of catchment land use practices. The lower reaches of the stream drain intensively farmed land and have dissolved oxygen (DO) levels of 10–50% saturation. The dominant riparian vegetation, Apium nodiflorum, provides a large organic loading by intercepting nutrients in run‐off and then decaying in the stream channel. Water quality and reaeration aspects of the stream were studied in order to explain the observed low DO levels. Measurements of the reaeration coefficient at 20°C, K₂ ²⁰, using methyl chloride (CH₃Cl) as a gas tracer, yielded values of 1.1–3.0 d^?1 for the upper part of the study reach and 15.5–16.2 d^?1 for the lower reach (overall average 12.5 ± 2.5 d^?1). These were in agreement with values inferred from single‐station diurnal curve analysis, which also showed that respiration was dominant in the lower reach where photo‐synthetic activity was inhibited by shade. The relatively large reaeration coefficients ensure that parts of the stream do not become anoxic at night time. Better riparian management and reduced nutrient inputs are likely to improve stream water quality.     

The glacial and interstadial sediments at the Burn of Benholm,Kincardineshire: evidence for onshore pre‐Devensian ice movement in northeast Scotland

Pebbly clays and diamictons containing marine shell fragments and peat lenses exposed beneath subglacially deposited Late Devensian till at the Burn of Benholm provide new insights into the glacial history of Quaternary sequences in eastern Scotland. The peat yielded pollen of interstadial affinity (including Bruckenthalia spiculifolia) and non‐finite radiocarbon dates. Comparisons with other pre‐Late Devensian pollen records in northern Scotland suggest that the peat lenses are remnants of an Early Devensian interstadial deposit, of Oxygen Isotope Substage 5c or 5a age. Reworked faunal assemblages in the shelly sediments include Quaternary marine molluscs of low boreal aspect, as well as Mesozoic and Palaeozoic microfossils. Amino acid ratios from fragments of Arctica islandica suggest that the shells are of Oxygen Isotope Stage 9 age or older. The fabric and composition of the shelly sediments are consistent with their emplacement as deformation till during the onshore movement of glacially transported rafts of marine sediment. Folded and sheared contacts between the shelly deposits, peat lenses and the overlying Late Devensian till indicate that the fossiliferous sediments were glacitectonised during the main Late Devensian glaciation, when ice moved from Strathmore and overrode the site from the southwest. British Geological Survey. © NERC 2000.     

A steady state of the disc dynamo

Abstract

We discuss the steady states of the αω-dynamo in a thin disc which arise due to α-quenching. Two asymptotic regimes are considered, one for the dynamo numberD near the generation thresholdD ₀, and the other for |D| ? 1. Asymptotic solutions for |D—D ₀| ? |D ₀| have a rather universal character provided only that the bifurcation is supercritical. For |D| ? 1 the asymptotic solution crucially depends on whether or not the mean helicity α, as a function ofB, has a positive root (hereB is the mean magnetic field). When such a root exists, the field value in the major portion of the disc is O(l), while near the disc surface thin boundary layers appear where the field rapidly decreases to zero (if the disc is surrounded by vacuum). Otherwise, when α = O(|B|^?s) for |B| → ∞, we demonstrate that |B| = O(|D|^1/s ) and the solution is free of boundary layers. The results obtained here admit direct comparison with observations of magnetic fields in spiral galaxies, so that an appropriate model of nonlinear galactic dynamos hopefully could be specified.     

泥石流源地土体应力应变特性对降雨响应过程的分析——以蒋家沟泥石流为例

根据对蒋家沟泥石流源地的崩塌、滑坡、散流坡,在旱季与雨季不同时段,降雨入渗后的土壤含水状况观测,以及泉水季节性变化,详细分析了泥石流源地崩塌、滑坡、散流坡土体的应力应变特性对降雨的响应过程差异.在雨季滑坡临空面和滑坡体内的土体含水量分别为6.67%、4.8%,滑坡活动主要是通过前缘剪出口崩塌方式补给下方沟床.崩塌体由于土体结构极为松散,在雨季该土体含水量通常高达8.85%～16%,使其土体的抗剪强度(C、φ)处于极限应力状态,一旦遇到降雨浸润和冲刷,迅速触变液化,转化为高浓度泥石流的侵蚀产沙过程.