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1.
Transformation of phosphorus species in settling seston and during early sediment diagenesis 总被引:9,自引:0,他引:9
Sequential P extraction was combined with electron microscop and X-ray spectroscopy to characterise various P species and to study their transformation in settling seston and in recent sediment. During early diagenesis most of the particulate P formed in the water was redissolved. No net transformation into species that would resist dissolution was observed.It was shown that
相似文献
• | the phosphorus (P) content and the P flux of settling particles varied seasonally over one order of magnitude |
• | particles became enriched with reductant soluble P (BD-P) while settling through the hypolimnion |
• | changes in BD-P were highly significantly correlated with changes in reductant soluble iron (BD-Fe) |
• | bacteria oxidising Fe and Mn seemed to be mainly responsible for this increase in P concentration |
• | other fractions including organic P did not change during sedimentation |
• | most of the organic P and of the Fe bound P and 70% of TP was released from the sediment during early diagenesis |
• | the sediment surface did not act as a trap for P migrating upwards from deeper sediment layers |
• | CaCO3 sedimentation contributed little to P sedimentation but significantly to the permanent burial of P. |
2.
Saving lives in earthquakes: successes and failures in seismic protection since 1960 总被引:1,自引:1,他引:0
Robin Spence 《Bulletin of Earthquake Engineering》2007,5(2):139-251
This paper will look at what we have and have not achieved in reducing the risks to human life from earthquakes in the last
50 years. It will review how success has been achieved in a few parts of the world, and consider what needs to be done by
the scientific and engineering community globally to assist in the future task of bringing earthquake risks under control.
The first part of the talk will re-examine what we know about the casualties from earthquakes in the last 50 years. Almost
80% of about 1 million deaths turn out to have been caused by just ten great earthquakes, together affecting a tiny proportion
of the territory at risk from heavy ground shaking. The disparity between richer and poorer countries is also evident, not
only in fatality rates, but also in their rates of change. But the existing casualty database turns out to be a very poor
basis for observing such differences, not only because of the small number of lethal events, but also because of the very
limited data on causes of death, types and causes of injury. These have been examined in detail in only a few, recent events.
All that can be said with certainty is that a few wealthier earthquake-prone countries or regions have made impressive progress
in reducing the risk of death from earthquakes, while most of the rest of the world has achieved comparatively little, and
in some areas the problem has become much worse. The second part of the paper looks in more detail at what has been achieved
country-by-country. Based on a new expert-group survey of key individuals involved in earthquake risk mitigation, it will
examine what are perceived to be the successes and failures of risk mitigation in each country or group of countries. This
survey will be used to highlight the achievements of those countries which have successfully tackled their earthquake risk;
it will examine the processes of earthquake risk mitigation, from campaigning to retrofitting, and it will consider to what
extent the achievement is the result of affluence, scientific and technical activity, political advocacy, public awareness,
or the experience of destructive events. It will ask to what extent the approaches pioneered by the global leaders can be
adopted by the rest. The final section of the talk will argue that it can be useful to view earthquake protection activity
as a public health matter to be advanced in a manner similar to globally successful disease-control measures: it will be argued
that the key components of such programmes—building in protection; harnessing new technology and creating a safety culture—must
be the key components of earthquake protection strategies also. It will consider the contribution which the scientific and
engineering community can make to bringing down today’s unacceptably high global earthquake risk. It will be suggested that
this role is wider than commonly understood and needs to include:
Building-in protection
Harnessing new technologies
Creating a safety culture
Examples of some of these actions will be given. International collaboration is essential to ensure that the resources and
expertise available in the richer countries is shared with those most in need of help. And perhaps the most important single
task for the engineering community is work to counter the widespread fatalistic attitude that future earthquakes are bound
to be at least as destructive as those of the past. 相似文献
• | Improving and simplifying information available for designers and self-builders of homes and infrastructure. |
• | Devising and running “building for safety” programmes to support local builders. |
• | Developing and testing cost-effective techniques for new construction and retrofit. |
• | Involvement in raising public awareness. |
• | Political advocacy to support new legislation and other actions. |
• | Prioritising action on public buildings, especially schools and hospitals. |
3.
Using the P-and S-wave arrivals from the 150 earthquakes distributed in Tibetan Plateau and its neighboring areas, recorded
by Tibetan seismic network, Sichuan seismic network, WWSSN and the mobile network situated in Tibetan Plateau, we have obtained
the average P-and S-wave velocity models of the crust and upper mantle for this region:
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 573–579, 1992. 相似文献
(1) | The crust of 70 km average thickness can be divided into two main layers: 16 km thick upper crust with P-wave velocity 5.55 km/s and S-wave velocity 3.25 km/s; and 54 km thick lower crust with P-wave velocity 6.52 km/s and S-wave velocity 3.76 km/s. |
(2) | The p-wave velocity at the upper most mantle is 7.97 km/s, and the S-wave 4.55 km/s. The low velocity layer in the upper mantle occurs approximately at 140 km deep with a thickness of about 55–62 km. The prominent velocity gradient beneath the LVZ is comparable to the gradient above it. |
4.
牛荻涛 《地震学报(英文版)》1995,8(1):155-159
StochasticmodelofbedrockearthquakemotionanddeterminationofitsparametersDi-TaoNIU(牛荻涛)(Xi'anUniversityofArchitecturalSciencean... 相似文献
5.
During a cruise on board RV Gauss in May/June 1988, joint investigations into organochlorine compounds, dissolved trace metals, petroleum hydrocarbons and basic hydrography were carried out at representative stations of the Baltic Monitoring Programme (BMP). The aim of the cruise was to study distribution patterns and — using previous data — to establish temporal trends if at all discernible.Each group of contaminants investigated showed specific characteristics, with differences even between compounds within the same group. The differences are due to:
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| - the partition of contaminants between dissolved and adsorbed form; |
| - the response to redox conditions; |
| - the influence of microbial decay, organic production or changes in speciation. |
6.
The spontaneous and evoked activity of electroreceptors were electrophysiologically studied. The results are:
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 380–386, 1991. 相似文献
1. | The spontaneous discharge rate ranged from 15 to 85 imp/s with a mode of 50 imp/s for 126 organs of 18 animals. |
2. | By analysis of periodic histograms and interspike interval histograms of responses to sinusoidal electric stimulations, the frequency response characteristic was determined. The frequency response curve shows a band pass type, the band width ranged from 5 Hz to 30 Hz and the best frequency is around 15 Hz. |
3. | The thresholds of responses for 47 organs were measured by injection of sinusoidal current into the organs. The threshold values were less than 0.1nA (61μV/cm) for 35 organs (74%), and less than 0.01nA (6.1 μV/cm) for the rest of 9 organs (19%). |
7.
Jo Ann Joselyn 《Pure and Applied Geophysics》1989,131(3):333-341
Based on published literature and the response to a questionnaire sent to geomagnetic field, ionospheric and magnetospheric researchers, several methods of choosing periods of quiet conditions based on geomagnetic records, as well as other observed parameters, have been identified. Caveats with respect to using geomagnetic indices to select quiet periods include the following:
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1. | Geomagnetic disturbances are strongly local. Even if the data from all available observatories indicate quiet behavior, there is the distinct possibility that some other location, not sampled, may be disturbed. |
2. | Geomagnetic indices are convenient but imperfect indicators of geomagnetic activity. Indices based on a quiet-day reference level have uncertainties comparable to the threshold value for quiet conditions. Indices representing average conditions during a 24-hr UT day may not be appropriate. |
3. | Geomagnetic activity does not fully reflect the range of possible factors that influence the ionosphere or magnetosphere. |
8.
Time series measurements from light vessel and coastal stations in the transition area of the Kattegat and the Baltic Sea are analyzed for the period August 1975 to March 1976. The data consist of daily sampled salinities from different depth levels and daily means of sea levels, surface current, and wind, respectively. The purpose of this paper is to examine the dynamics of the mass- and salt-transport during a major salt water inflow.The principal conclusions of this paper are that
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1) | the dynamics of the barotropic water exchange between the Kattegat and the Baltic Sea resembles that of a Helmholtz-resonator with a geostrophically controlled flow in the connecting channel; |
2) | the water exchange is forced by both the east component of the windstress over the North Sea and the windstress component in 30o true over the Baltic Sea; |
3) | the salinity in the upper layer of the Kattegat is governed by a permanent weak salt flux directed from the bottom to the surface layer and the outflow of less saline Baltic water into the upper layer of the Kattegat whereas the salinity of the Belt Sea is advected by the local currents along the main channel; |
4) | the most favorable conditions for a major salt inflow are initially a mean sea level of the Baltic lowered by about 30 cm followed by west winds steadily increasing over the following several ten days. Moreover, the hitherto used definition of a major salt water inflow is discussed and an improved definition is proposed. |
9.
The problem of fitting a probability distribution, here log-Pearson Type III distribution, to extreme floods is considered from the point of view of two numerical and three non-numerical criteria. The six techniques of fitting considered include classical techniques (maximum likelihood, moments of logarithms of flows) and new methods such as mixed moments and the generalized method of moments developed by two of the co-authors. The latter method consists of fitting the distribution using moments of different order, in particular the SAM method (Sundry Averages Method) uses the moments of order 0 (geometric mean), 1 (arithmetic mean), –1 (harmonic mean) and leads to a smaller variance of the parameters. The criteria used to select the method of parameter estimation are:
These criteria are transformed into value functions or fuzzy set membership functions and then three Multiple Criteria Decision Modelling (MCDM) techniques, namely, composite programming, ELECTRE, and MCQA, are applied to rank the estimation techniques. 相似文献
| - the two statistical criteria of mean square error and bias; |
| - the two computational criteria of program availability and ease of use; |
| - the user-related criterion of acceptability. |
10.
Akira Takada 《Bulletin of Volcanology》1988,50(2):106-118
The Subvolcanic structure of the central dike swarm associated with the Miocene Otoge ring complex and the Shitara igneous complex, central Japan, has been reconstructed. The central dike swarm was supplied from several aligned magma reservoirs. Flow lineations observed at the margin of the dikes converge towards a region that is regarded as a magma reservoir about 1–2 km below present sea level. The minimum diameter of the magma reservoir corresponds to the width of the central dike swarm, estimated to be about 3–4 km. The inferred magma reservoir of the Otoge ring complex, may have a zoned structure, as suggested by the flow lineations of dikes and the arrangement of cone sheets. Felsic magma occupied the upper part, about 1–2 km below present sea level, and basic magma the lower part, deeper than 2 km. The centre of the Shitara igneous complex is interpreted to be composed of several other shallow magma reservoirs. The distribution pattern in plan view of the central dike swarm is summarized from the frequency of dikes (defined by the number of dikes per kilometre in the direction normal to the trend of the dike swarm) and the variations of the different properties of individual dikes along the dike swarm. It has a plane of symmetry normal to the dike swarm above the magma reservoir. The patterns critical to a general understanding of the dike formation are:
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1. | A region of low dike frequency is present above the magma reservoir and a radial dike pattern occurs around the magma reservoir. |
2. | From both sides of the magma reservoir, the axes of high dike frequency extend symmetrically along the central zone of the dike swarm. |
3. | The number as well as the individual and total thickness of felsic dikes increases towards the magma reservoir. |
4. | The number of basic dikes increases towards both sides of the magma reservoir, while the individual thicknesses of basic dikes increase with distance from the magma reservoir. |
11.
Experimental study on the mechanism of non-synchronism of seismo-electromagnetic radiation precursors 总被引:1,自引:0,他引:1
IntroductionThrough20-oddyears’observationandstudyafterthe1976Tangshangreatearthquake,theseismo-electromagneticradiationprec... 相似文献
12.
A. Oya J. Navarro-Moreno J. C. Ruiz-Molina 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):317-326
An approach to the simulation of spatial random fields is proposed. The target random field is specified by its covariance
function which need not be homogeneous or Gaussian. The technique provided is based on an approximate Karhunen–Loève expansion
of spatial random fields which can be readily realized. Such an approximate representation is obtained from a correction to
the Rayleigh–Ritz method based on the dual Riesz basis theory. The resulting numerical projection procedure improves Rayleigh–Ritz
algorithm in the approximation of second-order random fields. Simulations are developed to illustrate the convergence and
accuracy of the method presented.
相似文献
J. C. Ruiz-MolinaEmail: |
13.
Davide D’Alimonte Dan Cornford 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(5):613-620
This paper, addresses the problem of novelty detection in the case that the observed data is a mixture of a known ‘background’ process contaminated with an unknown other process, which generates the outliers, or novel observations. The framework we
describe here is quite general, employing univariate classification with incomplete information, based on knowledge of the
distribution (the probability density function, pdf) of the data generated by the ‘background’ process. The relative proportion of this ‘background’ component (the prior ‘background’ probability), the pdf and the prior probabilities of all other components are all assumed unknown. The main contribution is a new classification scheme that
identifies the maximum proportion of observed data following the known ‘background’ distribution. The method exploits the Kolmogorov–Smirnov test to estimate the proportions, and afterwards data are Bayes
optimally separated. Results, demonstrated with synthetic data, show that this approach can produce more reliable results
than a standard novelty detection scheme. The classification algorithm is then applied to the problem of identifying outliers in the SIC2004 data set, in order
to detect the radioactive release simulated in the ‘joker’ data set. We propose this method as a reliable means of novelty
detection in the emergency situation which can also be used to identify outliers prior to the application of a more general
automatic mapping algorithm.
相似文献
Davide D’AlimonteEmail: |
Dan Cornford (Corresponding author)Email: |
14.
DSDP Hole 504B was drilled into 6 Ma crust, about 200 km south of the Costa Rica Rift, Galapagos Spreading Center, penetrating 1.35 km into a section that can be divided into four zones—Zone I: oxic submarine weathering; Zone II: anoxic alteration; Zones III and IV: hydrothermal alteration to greenschist facies. In Zone III there is intense veining of pillow basalts. Zone IV consists of altered sheeted dikes. Isotopic geochemical signatures in relation to the alteration zones are recorded in Hole 504B, as follows:
Alteration temperatures are as low as 10°C in Zones I and II based on oxygen isotope fractionation. Strontium isotopic data indicate that a circulation of seawater is much more restricted in Zone II than in Zone I. Fluid inclusion measurements of vein quartz indicate the alteration temperature was mainly 300 ± 20°C in Zones III and IV, which is consistent with secondary mineral assemblages.The strontium, oxygen, and hydrogen isotopic compositions of hydrothermal fluids which were responsible for the greenschist facies alteration in Zones III and IV are estimated to be 0.7037, 2‰, and 3‰, respectively. Strontium and oxygen isotope data indicate that completely altered portions of greenstones and vein minerals were in equilibrium with modified seawater under low water/rock ratios (in weight) of about 1.6. This value is close to that of the end-member hydrothermal fluids issuing at 21°N EPR.Basement rocks are not completely hydrothermally altered. About 32% of the greenstones in Zones III and IV have escaped alteration. Thus 1 g of fresh basalt including the 32% unaltered portion are required in order to make 1 g of end-member solution from fresh seawater in water-rock reactions. 相似文献
Zone | Depth(m) | Average87Sr/86Sr | Average δ18O (%o) | Average δD (%o) |
I | 275–550 | 0.7032 | 7.3 | −63 |
II | 550–890 | 0.7029 | 6.5 | −45 |
III | 890–1050 | 0.7035 | 5.6 | −31 |
IV | 1050–1350 | 0.7032 | 5.5 | −36 |
Full-size table
15.
Ram Ranjan Ruben N. Lubowski 《Stochastic Environmental Research and Risk Assessment (SERRA)》2005,19(5):315-325
We examine the management of livestock diseases from the producers‘ perspective, incorporating information and incentive asymmetries
between producers and regulators. Using a stochastic dynamic model, we examine responses to different policy options including
indemnity payments, subsidies to report at-risk animals, monitoring, and regulatory approaches to decreasing infection risks
when perverse incentives and multiple policies interact. This conceptual analysis illustrates the importance of designing
efficient combinations of regulatory and incentive-based policies.
相似文献
Ram RanjanEmail: |
16.
Amitrajeet A. Batabyal 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(3):253-257
Recently, Batabyal and Nijkamp (Environ Econ Policy Stud 7:39–51, 2005) have used a theoretical model of antibiotic use to study the relative merits of interventionist (antibiotics) and non-interventionist
(no antibiotics) treatment options. A key assumption in their paper is that the default treatment option is the interventionist
option. Because there are several instances in which this assumption is invalid, in this paper, we suppose that the default
treatment option is the non-interventionist option. Specifically, we first derive the long run average cost of treating a
common infection such as acute otitis media (AOM). Next, we show that there is a particular tolerance level and that when
a physician uses this tolerance level to determine when to administer the non-antibiotic medicine, the long run average cost
of treating the common infection under study is minimized.
相似文献
Amitrajeet A. BatabyalEmail: |
17.
Derivation of Photosynthetically Available Radiation from METEOSAT data in the German Bight with Neural Nets 总被引:1,自引:0,他引:1
Kathrin Schiller 《Ocean Dynamics》2006,56(2):79-85
Two different models, a Physical Model and a Neural Net (NN), are used for the derivation of the Photosynthetically Available
Radiation (PAR) from METEOSAT data in the German Bight; advantages and disadvantages of both models are discussed. The use
of a NN for derivation of PAR should be preferred to the Physical Model because by construction, a NN can take the various
processes determining PAR on a surface much better into account than a non-statistical model relying on averaged relations.
相似文献
Kathrin SchillerEmail: |
18.
Jamesina J. Simpson 《Surveys in Geophysics》2009,30(2):105-130
Advances in computing technologies in recent decades have provided a means of generating and performing highly sophisticated
computational simulations of electromagnetic phenomena. In particular, just after the turn of the twenty-first century, improvements
to computing infrastructures provided for the first time the opportunity to conduct advanced, high-resolution three-dimensional
full-vector Maxwell’s equations investigations of electromagnetic propagation throughout the global Earth-ionosphere spherical
volume. These models, based on the finite-difference time-domain (FDTD) method, are capable of including such details as
the Earth’s topography and bathymetry, as well as arbitrary horizontal/vertical geometrical and electrical inhomogeneities
and anisotropies of the ionosphere, lithosphere, and oceans. Studies at this level of detail simply are not achievable using
analytical methods. The goal of this paper is to provide an historical overview and future prospectus of global FDTD computational
research for both natural and man-made electromagnetic phenomena around the world. Current and future applications of global
FDTD models relating to lightning sources and radiation, Schumann resonances, hypothesized earthquake precursors, remote sensing,
and space weather are discussed.
相似文献
Jamesina J. SimpsonEmail: |
19.
A Survey of Techniques for Predicting Earthquake Ground Motions for Engineering Purposes 总被引:2,自引:0,他引:2
Over the past four or five decades many advances have been made in earthquake ground-motion prediction and a variety of procedures
have been proposed. Some of these procedures are based on explicit physical models of the earthquake source, travel-path and
recording site while others lack a strong physical basis and seek only to replicate observations. In addition, there are a
number of hybrid methods that seek to combine benefits of different approaches. The various techniques proposed have their
adherents and some of them are extensively used to estimate ground motions for engineering design purposes and in seismic
hazard research. These methods all have their own advantages and limitations that are not often discussed by their proponents.
The purposes of this article are to: summarise existing methods and the most important references, provide a family tree showing
the connections between different methods and, most importantly, to discuss the advantages and disadvantages of each method.
相似文献
John DouglasEmail: |
20.
Ocean/ice interaction at the base of deep-drafted Antarctic ice shelves modifies the physical properties of inflowing shelf
waters to become Ice Shelf Water (ISW). In contrast to the conditions at the atmosphere/ocean interface, the increased hydrostatic
pressure at the glacial base causes gases embedded in the ice to dissolve completely after being released by melting. Helium
and neon, with an extremely low solubility, are saturated in glacial meltwater by more than 1000%. At the continental slope
in front of the large Antarctic caverns, ISW mixes with ambient waters to form different precursors of Antarctic Bottom Water.
A regional ocean circulation model, which uses an explicit formulation of the ocean/ice shelf interaction to describe for
the first time the input of noble gases to the Southern Ocean, is presented. The results reveal a long-term variability of
the basal mass loss solely controlled by the interaction between waters of the continental shelf and the ice shelf cavern.
Modeled helium and neon supersaturations from the Filchner–Ronne Ice Shelf front show a “low-pass” filtering of the inflowing
signal due to cavern processes. On circumpolar scales, the simulated helium and neon distributions allow us to quantify the
ISW contribution to bottom water, which spreads with the coastal current connecting the major formation sites in Ross and
Weddell Seas.
相似文献
Christian B. RodehackeEmail: |