Nonlinearities in dynamo

By the example of the dynamo model in the rotating plane layer heated from below, the effects are examined that lead to the stabilization of an exponentially growing magnetic field in the magnetostrophic convection in passing from the kinematic dynamo mode to the nonlinear mode. The estimates of the energy redistribution in the spectrum are given, and the mechanisms of suppression of helicity are presented. Equalization of the field of velocity and the magnetic field is analyzed. The modes examined are close to those utilized in the up-to-date models of the planetary dynamo in the cores of planets.     

The distribution of trace elements in surface continental waters and the character of their migration in water

The results of studying the elemental composition of surface continental waters in the European Russia from tundra to arid zone are discussed. The relative concentrations of elements in the solid residue of waters from various natural-climatic zones are evaluated, and the enrichment or dispersion of continental waters by these elements are analyzed as compared with their clarkes in the rocks that occur in the catchment areas. The coefficients of migration in water are evaluated, and the major elements with respect to which surface waters enrich under anthropogenic load are identified. The territorial distribution of higher concentrations of the most hazardous elements in waters of lakes is characterized.     

Detecting organic tracers from biomass burning in the atmosphere.

This is a brief review key to the literature on the determination of organic tracers from biomass burning which are detectable even after long-range global transport in total extracts of atmospheric particles. The major tracers are thermal degradation products from the biopolymer cellulose, namely the didehydromonosaccharide derivatives levoglucosan, galactosan and mannosan and the resin acid derivative dehydroabietic acid, with minor beta-sitosterol. Dehydroabietic acid is emitted primarily from burning of conifer fuel and these tracers are found in most aerosol samples from the North American continent. Particulate matter from the atmosphere over oceanic areas contains organic tracers from both natural and biomass burning emissions. The major biomarker compounds characterized are natural products from continental vegetation consisting primarily of epicuticular wax components and trace components from biomass burning emissions. The presence of these tracers in atmospheric particulate matter over the ocean confirms the long-range transport of smoke from biomass burning off the continents.     

The stress-field in the alpine-mediterranean region

The neotectonic stress field in the Alpine-Mediterranean region is investigated. It is shown that information on this field can be obtained from insitu measurements, from earthquake fault plane solutions, from the orientation of joints and even from valley trends. The available data are collected and collated. It is shown that there is a general correspondence in any one area between these types of data. Maps showing the orientations of the principal stress directions are given.     

Volcanic ash soils in New Zealand

Ash and lapilli derived from Holocene and Late Pleistocene volcanic cruptions cover approximately half of the North Island of New Zealand. Deposits from 16 separate series of showers are recognised in the surface soils and areas with 3 inches and more of each ash bed have been mapped out during soil surveys. These and other shower deposits are also recognised and described in fossil soils. The effects of the volcanic ashes on soil properties are related to the thickness and frequency of deposition, to mineral composition, and to the period of exposure to soil formation. Soils formed from shower deposits of Holocene age are extensive and have characteristic properties of friability, fine granular structure, deep humic topsoils and slippery non-sticky clays. The clays are chiefly amorphous and responsible for the notable practical properties of free drainage, high moisture retention, low bulk density, and critical limits of stability under pressure. In New Zealand the development of these characteristies increases with time up to about 15,000 years and then decreases with the crystallisation of the clays to halloysite. Soils formed from Late Pleistocene volcanic ashes are high in halloysite clay and with increasing age resemble soils formed from marine sedimentary rocks. Differing degrees of development of the characteristics are shown in the soil classification. The soils from volcanic ash are widely used for crop, pasture or forestry production. More intensive permanent usage depends on more detailed knowledge of the materials which will be obtained through combined volcanological and pedological research.     

Crustal loading in vertical GPS time series in Fennoscandia

We compare time series of vertical position from GPS with modelled vertical deformation caused by variation in continental water storage, variation in the level of the Baltic Sea, and variation in atmospheric pressure. Monthly time series are used. The effect of continental water storage was calculated from three different global models. The effect of non-tidal variation in Baltic Sea level was calculated using tide gauge observations along the coasts. Atmospheric loading was computed from a numerical weather model. The loading time series are then compared with three different GPS time series at seven stations in Fennoscandia. A more detailed analysis is computed at three coastal stations. When the monthly GPS time series are corrected using the load models, their root-mean-square scatter shows an improvement between 40 and 0%, depending on the site and on the GPS solution. The modelled load effect shows a markedly seasonal pattern of 15 mm peak-to-peak, of which the uncorrected GPS time series reproduce between 60 and 0%.     

HPLC in der Wasseranalytik

Selected journals are scrutinized for the period from 1980 to 1986 with respect to the application of HPLC to the detection of organic substances in water and the state of knowledge deducible from that is represented. Various chromatographic methods are compared with respect to their sensitivity and suitability for certain groups of substances. The structure of modern separation columns and of different detector systems as well as possible modes of operation are described. A large number of specific examples of application are given in tabular form.     

Estimation of periodicities in hydrologic data

Periodicites in hydrologic data are frequently estimated and studied. In some cases the periodic components are subtracted from the data to obtain the stochastic components. In other cases the physical reasons for the occurrence of these periodicities are investigated. Apart from the annual cycle in the hydrologic data, periods corresponding to the 11 year sunspot cycle, the Hale cycle and others have been detected.The conclusions from most of these studies depend on the reliability and robustness of the methods used to detect these periodicities. Several spectral analysis methods have been proposed to investigate periodicities in time series data. Several of these have been compared to each other. The methods by Siddiqui and Wang and by Damsleth and Spjotvoll, which are stepwise procedures of spectrum estimation, have not been evaluated.     

海南东北部地区地壳地震各向异性特征初步研究

基于海南省地震台网2000～2013年的区域地震波形数据,用剪切波分裂系统分析方法（SAM）获得了海南琼东北部地区“九五”数字台网中2个台站的剪切波分裂参数。结果表明,快剪切波偏振优势方向代表了原地最大主压应力方向。七星岭台NE方向的快剪切波偏振优势方向与区域水平主压应力场方向不一致,与NE走向的断裂一致,体现了局部构造和局部应力场的复杂性;青山岭NNE向的快剪切波偏振优势方向揭示了NNE走向断裂的构造意义。同时,本研究证实,位于活动断裂上或几条活动断裂交汇部位的台站的快剪切波偏振优势方向,与对所选用的小地震起控制作用的活动断裂走向一致,并且快剪切波偏振优势方向较为离散,反映了该区域复杂的断裂构造和应力分布特征。     

Exposure concentration statistics in the subsurface transport

The concentration fluctuations resulting from hazardous releases in the subsurface are modeled through the concentration moments. The local solute exposure concentration, resulting from the heterogeneous velocity field and pore scale dispersion in the subsurface, is a random function characterized by its statistical moments. The approximate solution to the exact equation that describes the evolution of concentration standard moments in the aquifer transport is proposed in a recursive form. The expressions for concentration second, third and fourth central moments are derived and evaluated for various flow and transport conditions. The solutions are sought by starting from the exact upper bound solution with the zero pore scale dispersion and introducing the physically based approximation that allows the inclusion of the pore scale dispersion resulting in simple closed-form expressions for the concentration statistical moments. The concentration moments are also analyzed in the relative and absolute frame of reference indicating their combined importance in the practical cases of the subsurface contaminant plume migration. The influence of pore scale dispersion with different source sizes and orientations are analyzed and discussed with respect to common cases in the environmental risk assessment problems. The results are also compared with the concentration measurements of the conservative tracer collected in the field experiments at Cape Cod and Borden Site.     

信息熵在地下流体资料处理中的应用

简要介绍了信息熵的原理及其方法，并对八宝山断裂带逸出氡和昌黎台的水位资料进行处理，结果表明，用信息熵的原理和方法从前兆观测资料中提取地震前兆异常信息是可行的，八宝山断裂带逸出氡的信息熵减熵异常对应地震较好，分别从氡日均值和五日均值中提取的信息熵都是能得出一些很有意义的异常信息，但五日均值物熵值更明显，直观，昌黎水位处理结果也说明地震前后信息熵会出现较为明显的减熵异常，并且水位观测值势变化对信息熵影响不大。     

The damage mechanics of brittle solids in compression

The development of microcrack damage in brittle solids in compression is analyzed, using a simple model. The model is developed from recent detailed analysis of the initiation, propagation and linkage of microfractures from pre-existing cracks, voids, or other inhomogeneities. It describes the evolution of damage with strain and from it a criteria for failure can be established. The results are used to construct failure surfaces in stress space which combine information about brittle failure with data describing the onset of plastic yielding. Such failure surfaces are constructed for a number of rocks and are compared with previously published experimental data.     

山西地区地壳剪切波分裂特征

通过对山西数字地震台网2000年6月—2012年12月的波形记录资料的分析, 使用剪切波分裂系统分析方法, 即SAM综合分析方法, 获得了山西地区18个数字地震台站的快剪切波偏振结果. 结果表明： 位于活动断裂上的台站的快剪切波偏振优势方向与活动断裂的走向基本一致; 个别距离断裂较远的台站的快剪切波偏振优势方向与震源机制解及GPS主压应变方向完全一致; 少数位于几条断裂交汇处的台站的快剪切波偏振优势方向则较为复杂, 与活动断裂的走向和GPS主压应变方向均不一致, 反映了该地区断裂背景和应力分布特征的复杂性.     

Modeling flocculation in a hypertidal estuary

When fine particles are involved, cohesive properties of sediment can result in flocculation and significantly complicate sediment process studies. We combine data from field observations and state-of-the-art modeling to investigate and predict flocculation processes within a hypertidal estuary. The study site is the Welsh Channel located at the entrance of the Dee Estuary in Liverpool Bay. Field data consist of measurements from a fixed site deployment during 12–22 February 2008. Grain size, suspended sediment volume concentration, and current velocity were obtained hourly from moored instruments at 1.5 m above bed. Near-bottom water samples taken every hour from a research vessel are used to convert volume concentrations to mass concentrations for the moored measurements. We use the hydrodynamic model Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS) coupled with the turbulence model General Ocean Turbulence Model (GOTM) and a sediment module to obtain three-dimensional distributions of suspended particulate matter (SPM). Flocculation is identified by changes in grain size. Small flocs were found during flood and ebb periods—and correlate with strong currents—due to breakup, while coarse flocs were present during slack waters because of aggregation. A fractal number of 2.4 is found for the study site. Turbulent stresses and particle settling velocities are estimated and are found to be related via an exponential function. The result is a simple semiempirical formulation for the fall velocity of the particles solely depending on turbulent stresses. The formula is implemented in the full three-dimensional model to represent changes in particle size due to flocculation processes. Predictions from the model are in agreement with observations for both settling velocity and SPM. The SPM fortnight variability was reproduced by the model and the concentration peaks are almost in phase with those from field data.     

Magnetic fields in galaxy halos and their importance

Abstract

The observational facts about magnetic fields in galactic halos are reviewed. The existence, origin and significance of poloidal field components are described. Observational evidence that magnetic fields channel winds from active galactic centres is discussed. Field strengths adduced from the radio polarizations of edge-on galaxies are given. Priorities for future research are suggested.     

Determining sea level change in the German Bight

Regional mean sea level changes in the German Bight are considered. Index time series derived from 15 tide gauge records are analysed. Two different methods for constructing the index time series are used. The first method uses arithmetic means based on all available data for each time step. The second method uses empirical orthogonal functions. Both methods produce rather similar results for the time period 1924–2008. For this period, we estimate that regional mean sea level increased at rates between 1.64 and 1.74 mm/year with a 90% confidence range of 0.28 mm/year in each case. Before 1924, only data from a few tide gauges are available with the longest record in Cuxhaven ranging back till 1843. Data from these tide gauges, in particular from Cuxhaven, thus receive increasingly more weight when earlier years are considered. It is therefore analysed to what extent data from Cuxhaven are representative for the regional sea level changes in the German Bight. While this cannot be clarified before 1924, it is found that this is not the case from 1924 onwards when changes in Cuxhaven can be compared to that derived from a larger data set. Furthermore, decadal variability was found to be substantial with relatively high values towards the end of the analysis period. However, these values are not unusual when compared to earlier periods.     

中国火山温泉气体地球化学特征及其在火山监测中的应用

中国火山温泉主要分布在吉林长白山、云南腾冲和黑龙江五大连池等火山区。这些火山虽然处于休眠状态,但大面积的温泉分布指示着岩浆房存在的可能性。本文总结了前人研究成果,分析了中国主要火山区温泉气体地球化学特征,并探讨了温泉气体在火山监测中的应用。长白山、腾冲和五大连池火山区温泉气体地球化学性质类似,都以CO₂为主要气体,含量在80%以上,最高可达99%以上,其它气体组分包括CH₄、N₂、O₂、SO₂、H₂S、He和H₂等。长白山火山温泉气体中氦同位素比值（3He/4He）最高,约为4—6R_A,CO₂中碳同位素比值（δ13C）为-7.9‰—-1.3‰,CH₄中碳同位素为-48.0‰—-28.7‰;腾冲火山温泉气体氦同位素比值为3—5.5R_A,CO₂中的碳同位素为-6.49‰—-2.07‰,CH₄中碳同位素为-23.5‰—-9.3‰;五大连池火山温泉气体氦同位素比值约为3R_A,CO₂中的碳同位素比值为-9.6‰—-3.1‰,CH₄中碳同位素为-47.2‰—-44.4‰。3个火山区的温泉气体均显示地幔来源的岩浆气体特征,并在上升运移过程中受地壳或古俯冲物质的影响。     

地震模拟振动台控制系统的发展

地震模拟振动台作为结构抗震研究重要的试验设备之一,从20世纪60年代至今,经历了从线性到非线性、时不变到时变、模拟控制到数字控制、位移控制到加速度高级算法控制的发展过程.本文从建模方法、参数识别和控制算法三个方面回顾了地震模拟振动台控制系统研究的发展历程与现状,并阐述了地震模拟振动台控制系统的发展趋势,即试件与台面动力耦合模型、高性能参数识别、控制器参数自整定、强非线性高级控制算法、振动台台阵系统控制算法.     

Palaeomagnetism and tectonics in Umbria,Italy

Detailed records of palaeomagnetic directions from two Upper Cretaceous Umbrian sections are compared with the composite section compiled by Van den Berg et al. [1]. In addition to these sections, fifty-one geographically distributed sites have been studied magnetically and palaeontologically. The Late Miocene-Pliocene fold belt of the Umbrian Apennines is arcuate in outcrop, being convex toward the east. The fold axes are generally tangential to the Umbrian arc, which can be divided into a northern northwestern-trending part and a southern northeastern-trending part. Sites from the north have more westerly declinations than those from the south. The differences are significant at the 95% probability level and most probably reflect the bending of originally straight fold axes or the development of fold axes with initial curvature. The palaeomagnetic directions from Umbria provide important information concerning the Umbrian tectonic deformation, but are not applicable to the Italian autochthon.     

Analysis of nonstationarity in low flow in the Loess Plateau of China

An approach for nonstationary low‐flow frequency analysis is developed and demonstrated on a dataset from the rivers on the Loess Plateau of China. Nonstationary low‐flow frequency analysis has drawn significant attention in recent years by establishing relationships between low‐flow series and explanatory variables series, but few studies have tested whether the time‐varying moments of low flow can be fully described by the time‐varying moments of the explanatory variables. In this research, the low‐flow distributions are analytically derived from the 2 basic explanatory variables—the recession duration and the recession coefficient—with the assumption that the recession duration and recession coefficient variables follow exponential and gamma distributions, respectively; the derived low‐flow distributions are applied to test whether the time‐varying moments of explanatory variables can explain the nonstationarities found in the low‐flow variable. The effects of ecosystem construction measures, that is, check dam, terrace, forest, and grassland, on the recession duration and recession coefficient are further discussed. Daily flow series from 11 hydrological stations from the Loess Plateau are used and processed with a moving average technique. Low‐flow data are extracted following the pit under threshold approach. Six of the 11 low‐flow series show significant nonstationarities at the 5% significance level, and the trend curves of the moments of low flow are in close agreement with the curves estimated from the derived distribution with time‐dependent moments of the recession duration and time‐constant moments of the recession coefficient. It is indicated that the nonstationarity in the low‐flow distribution results from the nonstationarity in the recession duration in all 6 cases, and the increase in the recession duration is resulted from large‐scale ecosystem constructions rather than climate change. The large‐scale ecosystem constructions are found to have more influence on the decrease in streamflow than on the increase in watershed storage, thus resulting in the reduction of low flow. A high return period for the initial fixed design value decreases dramatically with an increasing recession duration.