共查询到20条相似文献，搜索用时 843 毫秒
1.
F. Ashkar N. El Jabi M. Issa 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(2):97-116
: The knowledge of the volume and duration of low-flow events in river channels is essential for water management and the
design of hydraulics structures. In this study, both preceding characteristics, X
1 and X
2, are considered simultaneously via two types of bivariate distributions whose marginals are exponential. One of these bivariate
distributions has been presented by Nagao and Kadoya (1971) and the other has been used by Singh and Singh (1991) to the study
of rainfall intensity and rainfall depth. The results are applied to the low-flow series (“peaks-below-threshold”) of Lepreau
River (station 01AQ001) in New Brunswick, Canada. These results show that the model that was successfully employed by Singh
and Singh (1991) to study rainfall, presents certain difficulties when a very strong correlation, ρ, between the two random
variables X
1 and X
2, exists. The model by Nagao and Kadoya (1971) seems to be more satisfactory for such situations, although this model seems
also to be quite sensitive to variations in ρ. 相似文献
2.
S. Yue 《Stochastic Environmental Research and Risk Assessment (SERRA)》2001,15(3):244-260
The open literature reveals several types of bivariate exponential distributions. Of them only the Nagao–Kadoya distribution
(Nagao and Kadoya, 1970, 1971) has a general form with marginals that are standard exponential distributions and the correlation
coefficient being 0≤ρ<1. On the basis of the principle that if a theoretical probability distribution can represent statistical
properties of sample data, then the computed probabilities from the theoretical model should provide a good fit to observed
ones, numerical experiments are executed to investigate the applicability of the Nagao–Kadoya bivariate exponential distribution
for modeling the joint distribution of two correlated random variables with exponential marginals. Results indicate that this
model is suitable for analyzing the joint distribution of two exponentially distributed variables. The procedure for the use
of this model to represent the joint statistical properties of two correlated exponentially distributed variables is also
presented. 相似文献
3.
Saralees Nadarajah Samuel Kotz 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(3):164-170
Motivated by environmental applications, we derive the exact distributions of R = X+Y, P = X
Y and W = X/(X+Y) and the corresponding moment properties when X and Y follow Downton’s bivariate exponential distribution. The expressions turn out to involve several special functions. For practical
purposes, we also provide extensive tabulations of the percentage points associated with the distributions. 相似文献
4.
Probabilistic seismic hazard for Mainland Portugal was re-evaluated in order to perform its disaggregation. Seismic hazard
was disaggregated considering different spaces of random variables, namely, univariate conditional hazard distributions of
M (magnitude), R (source-to-site distance) and ε (deviation of ground motion to the median value predicted by an attenuation model), bivariate conditional hazard distributions
of M–R and X–Y (seismic source latitude and longitude) or multivariate conditional hazard distributions of M–R–ε and M–(X–Y)–ε. The main objective of the present work was achieved, as it was possible, based on the modal values of the above mentioned
distributions, to characterize the scenarios that dominate some seismic hazard levels of the 278 Mainland Portuguese counties.
In addition, results of 4D disaggregation analysis, in M–(X–Y)–ε, pointed out the existence of one geographic location shared by the dominant scenario of most analyzed counties, especially
for hazard levels correspondent to high return periods. Those dominant scenarios are located offshore at a distance of approximately
70 km WSW of S. Vicente cape. On the other hand, the lower the return period the higher is the number of modal scenarios in
the neighbourhood of the analyzed site. One may conclude that modal scenarios reproduce hazard target values in each site
with great accuracy enabling the applications derived from those scenarios (e.g. loss evaluation) to be associated to a hazard
level exceedance probability. 相似文献
5.
Francesco Serinaldi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(5):695-696
A comprehensive parametric approach to study the probability distribution of rainfall data at scales of hydrologic interest
(e.g. from few minutes up to daily) requires the use of mixed distributions with a discrete part accounting for the occurrence
of rain and a continuous one for the rainfall amount. In particular, when a bivariate vector (X, Y) is considered (e.g. simultaneous observations from two rainfall stations or from two instruments such as radar and rain
gauge), it is necessary to resort to a bivariate mixed model. A quite flexible mixed distribution can be defined by using
a 2-copula and four marginals, obtaining a bivariate copula-based mixed model. Such a distribution is able to correctly describe
the intermittent nature of rainfall and the dependence structure of the variables. Furthermore, without loss of generality
and with gain of parsimony this model can be simplified by some transformations of the marginals. The main goals of this work
are: (1) to empirically explore the behaviour of the parameters of marginal transformations as a function of time scale and
inter-gauge distance, by analysing data from a network of rain gauges; (2) to compare the properties of the regression curves
associated to the copula-based mixed model with those derived from the model simplified by transformations of the marginals.
The results from the investigation of transformations’ parameters are in agreement with the expected theoretical dependence
on inter-gauge distance, and show dependence on time scale. The analysis on the regression curves points out that: (1) a copula-based
mixed model involves regression curves quite close to some non-parametric models; (2) the performance of the parametric regression
decreases in the same cases in which non-parametric regression shows some instability; (3) the copula-based mixed model and
its simplified version show similar behaviour in term of regression for mid-low values of rainfall.
An erratum to this article can be found at 相似文献
6.
Calculation of the parameters of georesistivi－ty anisotropy and case history of earthquake precursors 总被引：4，自引：0，他引：4
Ｃａｌｃｕｌａｔｉｏｎｏｆｔｈｅｐａｒａｍｅｔｅｒｓｏｆｇｅｏｒｅｓｉｓｔｉｖｉ┐ｔｙａｎｉｓｏｔｒｏｐｙａｎｄｃａｓｅｈｉｓｔｏｒｙｏｆｅａｒｔｈｑｕａｋｅｐｒｅｃｕｒｓｏｒｓＦＵ－ＹＥＱＩＡＮ１）（钱复业），ＹＵ－ＬＩＮＺＨＡＯ１）（赵玉林）ａ... 相似文献
7.
The parameters of rocks in ultrahigh-presure state are very important to understanding the geodynamics and explosion engineering
of rocks. In these experiments the plane wave dynamite lenses were used to drive the flying plates. The flying plate hits
the target and produces the ultrahigh-pressure shock wave. The propagation velocity and the particle velocity of shock wave
in rock samples were measured by probes, and the relation between density of rocks and pressure was obtained by Rankine-Hugoniot
formulas. The maximum pressure in experiments was higher than 70 GPa. The ultrahigh-pressure state formulas obtained are:
Limestoneρ=3.22+0.016p; Graniteρ=3.20+0.024p. In which the unit for ρ is g/cm3, the unit forp is GPa.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 96–103, 1991. 相似文献
8.
Ａｌｉｇｎｍｅｎｔｓｉｌｋｗｏｒｍｓａｓｓｅｉｓｍｉｃａｎｉｍａｌａｎｏｍａｌｏｕｓｂｅｈａｖｉｏｒ（ＳＡＡＢ）ａｎｄｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｍｏｄｅｌｏｆａｆａｕｌｔ：ａｔｈｅｏｒｙａｎｄｌａｂｏｒａｔｏｒｙｅｘｐｅｒｉｍｅｎｔＭＯＴＯ... 相似文献
9.
This paper aims to analyse the geoelectrical resistivityρ
s
data on the dipole electrode sounding, which were firstly accumulated from the earthquake prone region in China. The analyses
on the one order difference value of the geoelectrical resistivity indicated that, firstly, more than 4 percent of theρ
s
data reveals the precursors by 3 to 76 days ahead the earthquakes occurring, with the magnitude range of 4 ≤M ≤ 6. 4, in a region of 100 km around the station, and secondly, the results revealed that the seasonal variation ofρ
s
data were slight.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 211–219, 1992. 相似文献
10.
Songbai Song Vijay P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):425-444
This study aims to model the joint probability distribution of periodic hydrologic data using meta-elliptical copulas. Monthly
precipitation data from a gauging station (410120) in Texas, US, was used to illustrate parameter estimation and goodness-of-fit
for univariate drought distributions using chi-square test, Kolmogorov–Smirnov test, Cramer-von Mises statistic, Anderson-Darling
statistic, modified weighted Watson statistic, and Liao and Shimokawa statistic. Pearson’s classical correlation coefficient
r
n
, Spearman’s ρ
n, Kendall’s τ, Chi-Plots, and K-Plots were employed to assess the dependence of drought variables. Several meta-elliptical copulas and
Gumbel-Hougaard, Ali-Mikhail-Haq, Frank and Clayton copulas were tested to determine the best-fit copula. Based on the root
mean square error and the Akaike information criterion, meta-Gaussian and t copulas gave a better fit. A bootstrap version
based on Rosenblatt’s transformation was employed to test the goodness-of-fit for meta-Gaussian and t copulas. It was found
that none of meta-Gaussian and t copulas considered could be rejected at the given significance level. The meta-Gaussian copula
was employed to model the dependence, and these results were found satisfactory. 相似文献
11.
Features and physical process of the dynamic evolution pattern of ground resistivity precursor front
ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅ１９６０′ｓ,ｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍｏｄｅｒｎｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙｈａｓｇｒａｄｕａｌｙｍａｄｅｉｔｐｏｓｉｂｌｅｔｏｐｒｅｄｉｃｔｅａｒｔｈｑｕａｋｅｓａｎｄｈａｓｐｒｏｍｏｔ... 相似文献
12.
Generous statistical tests 总被引：1，自引：1，他引：0
T. V. Hromadka II R. J. Whitley S. B. Horton M. J. Smith J. M. Lindquist 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(1):9-12
A common statistical problem is deciding which of two possible sources, A and B, of a contaminant is most likely the actual
source. The situation considered here, based on an actual problem of polychlorinated biphenyl contamination discussed below,
is one in which the data strongly supports the hypothesis that source A is responsible. The problem approach here is twofold:
One, accurately estimating this extreme probability. Two, since the statistics involved will be used in a legal setting, estimating
the extreme probability in such a way as to be as generous as is possible toward the defendant’s claim that the other site
B could be responsible; thereby leaving little room for argument when this assertion is shown to be highly unlikely. The statistical
testing for this problem is modeled by random variables {X
i
} and the corresponding sample mean the problem considered is providing a bound ɛ for which for a given number a
0. Under the hypothesis that the random variables {X
i
} satisfy E(X
i
) ≤ μ, for some 0 < μ < 1, statistical tests are given, described as “generous”, because ɛ is maximized. The intent is to
be able to reject the hypothesis that a
0 is a value of the sample mean while eliminating any possible objections to the model distributions chosen for the {X
i
} by choosing those distributions which maximize the value of ɛ for the test used. 相似文献
13.
Jiří Horák 《Studia Geophysica et Geodaetica》1970,14(1):83-92
Zusammenfassung Wir studieren die Folgen eines Modells der unter der Voraussetzung konstruierten turbulenten Diffusion, dass die zuf?llige
FunktionX(X
0,t) eine Markowsche Funktion ist und dass der Mittelwert der Konzentration
von der Beimengung der zweiten Kolmogorowschen Gleichung entspricht. Das Verlassen dieser Vorstellung führt zur Schlussfolgerung,
dass man den Zustand des „Mikroobjekts” (Teilchens) für jedent-Wert als eine Klasse von Gr?ssenwerten betrachten kann, die es gleichzeitig prinzipiell m?glich ist mit beliebiger Genauigkeit
zu messen. Eine Abwendung von der statistischen Relation der Unbestimmtheit wird durch die Existenz von verborgenen Parametern
bei den diffusions- und Turbulenzprozessen verursacht. ihr Vorkommen ruft jedoch keinen übergang zum Kausalmodell des Prozesses
hervor; die FunktionX(X
0,t) (Lagrangesche Charakteristik vom Fliessen einer unkompressibeln Flüssigkeit) bleibt immer eine zuf?llige Funktion. Die Klasse
der m?glichen Wahrscheinlichkeitswerte des übergangsp bildet jedoch keinen Markowschen Prozess im entsprechenden Phasenraum.
Address: Boční II, Praha 4-Spořilov. 相似文献
Address: Boční II, Praha 4-Spořilov. 相似文献
14.
Zhiping Song Xiangchu Yin Shirong Mei Yucang Wang Can Yin Huihui Zhang Langping Zhang 《Pure and Applied Geophysics》2006,163(9):1991-2009
Based on the three-dimensional elastic inclusion model proposed by Dobrovolskii, we developed a rheological inclusion model
to study earthquake preparation processes. By using the Corresponding Principle in the theory of rheologic mechanics, we derived
the analytic expressions of viscoelastic displacement U(r, t) , V(r, t) and W(r, t), normal strains εxx (r, t), εyy (r, t) and εzz (r, t) and the bulk strain θ (r, t) at an arbitrary point (x, y, z) in three directions of X axis, Y axis and Z axis produced by a three-dimensional inclusion in the semi-infinite rheologic medium defined by the standard linear rheologic
model. Subsequent to the spatial-temporal variation of bulk strain being computed on the ground produced by such a spherical
rheologic inclusion, interesting results are obtained, suggesting that the bulk strain produced by a hard inclusion change
with time according to three stages (α, β, γ) with different characteristics, similar to that of geodetic deformation observations, but different with the results of
a soft inclusion. These theoretical results can be used to explain the characteristics of spatial-temporal evolution, patterns,
quadrant-distribution of earthquake precursors, the changeability, spontaneity and complexity of short-term and imminent-term
precursors. It offers a theoretical base to build physical models for earthquake precursors and to predict the earthquakes. 相似文献
15.
In most lakes, phosphorus (P) is the nutrient controlling the trophic state. Thus, for effective control of eutrophication, the uncertainty in P-loading should be encoded as a probability density function (pdf). Specifically, the pdf of P-loading Y from non-point agricultural sources is sought by means of an event-based stochastic model.P-loading events are triggered by precipitation events (X1, X2, T), in which X1 is the rainfall amount, X2 the duration, and T the interarrival time between events. (X1, X2) are dependent random variables, while T is assumed to be exponentially distributed. The precipitation event causes runoff, which carries dissolved P into the lake with a concentration C1 and sediment yield, Z, which carries fixed or sorbed P into the lake in a fraction C2 of Z. Seasonal loading of P is calculated by adding random numbers of random variables. The model accounts separately for dissolved P and sorbed P. Explicit expressions are given for the mean and variance of each type of P-loadings. The case study of a sub-watershed of Lake Balaton, Hungary, is used to illustrate the methodology. Precipitation data, empirical rainfall-runoff-sediment yield relationships and a small number of observations of events are used to calibrate the model and estimate the means and variances of loading per event and per season. Then a simulation method is used to estimate complete pdf of these random variables. Use of the model for alternative methods of controlling P-loading is briefly discussed, as well as the economics of control. 相似文献
16.
In transversely isotropic media with a vertical symmetry axis (VTI), the converted-wave (C-wave) moveout over intermediate-to-far
offsets is determined by four parameters. These are the C-wave stacking velocity V
C2, the vertical and effective velocity ratios γ
0and γ
eff, and the anisotropic parameter X
eff. We refer to the four parameters as the C-wave stacking velocity model. The purpose of C-wave velocity analysis is to determine
this stacking velocity model.
The C-wave stacking velocity model V
C2, γ
0, γ
geff, and X
eff can be determined from P- and C-wave reflection moveout data. However, error propagation is a severe problem in C-wave reflection-moveout
inversion. The current short-spread stacking velocity as deduced from hyperbolic moveout does not provide sufficient accuracy
to yield meaningful inverted values for the anisotropic parameters. The non-hyperbolic moveout over intermediate-offsets (x/z
from 1.0 to 1.5) is no longer negligible and can be quantified using a background γ. Non-hyperbolic analysis with a γ correction over the intermediate offsets can yield V
C2 with errors less than 1% for noise free data. The procedure is very robust, allowing initial guesses of γ with up to 20% errors. It is also applicable for vertically inhomogeneous anisotropic media. This improved accuracy makes
it possible to estimate anisotropic parameters using 4C seismic data. Two practical work flows are presented for this purpose:
the double-scanning flow and the single-scanning flow. Applications to synthetic and real data show that the two flows yield
results with similar accuracy but the single-scanning flow is more efficient than the double-scanning flow.
This work is funded by the Edinburgh Anisotropy Project of the British Geological Survey.
First Author
Li Xiangyang, he is currently a professorial research seismologist (Grade 6) and technical director of the Edinburgh Anisotropy Project
in the British Geological Survey. He also holds a honorary professorship multicomponent seismology at the School of Geosciences,
University of Edinburgh. He received his BSc(1982) in Geophysics from Changchun Geological Institute, China, an MSc (1984)
in applied geophysics from East China Petroleum Institute (now known as the China University of Petroleum), and a PhD (1992)
in seismology from the University of Edinburgh. During 1984–1987, he worked as a lecturer with the East China Petroleum Institute.
Since 1991, he has been employed by the British Geological Survey. His research interests include seismic anisotropy and multicomponent
seismology. 相似文献
17.
A comprehensive analysis of Kamchatka seismicity for the period 2005–2007 using the regional catalog
We characterize the Kamchatka seismicity for the period 2005–2007. Regional catalogs of Kamchatka earthquakes were used to
develop 2D distributions of parameters of background seismicity. The characteristics we consider include the activity A
10, the slope of the recurrence curve γ, the parameters involved in the methods RTL, ΔS, and the “Z-function”, as well as the control of earthquake clustering. We have detected the space-time agreement between the anomalies
exhibited by several parameters. 相似文献
18.
In this paper, the coefficients of Parkinson vectora, b and the in-phase partA
r, Br and quadrature-phase partA
i, Bi of transter functions are calculated by using two kinds of data processing methods, respectively. The results of both methods
are close to each other. All these six parameters above are low in value, showing that the electric structure in Heze area
is rather uniform. It seems that the anomalous changes appeared in both results, and the values of parameters decrease before
and after Heze earthquake.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 113–120, 1991. 相似文献
19.
在具有垂直对称轴横向各向同性介质中，利用四种参数来确定中间至远偏移距转换波（C-波）动校正。它们是C-波叠加速度Vc2，垂直速度比和有效速度比γ0和γeff以及各向异性参数χeff。我们将这四种参数作为C波叠加速度模型。C-波速度分析的目的就是确定这种叠加速度模型。C-波叠加速度模型Vc2，γ0，γeff，和χeff可以由P-波和C-波反射动校正资料获得。然而错误的传播是C-波反射动校正反演中的严重问题。当前短排列叠加速度由于是从双曲线动校正推算而得，因而其精度不足以为各向异性参数提供有意义的反演值。中间偏移非双曲线动校正不再被人们所勿略，而是可以用一个背景γ加以量化。非双曲线分析通过中间偏移距的γ校正量可以产生Vc2，若数据不含燥音，其误差小于1％。方法稳健，允许γ启始假定值的误差达20％。该方法也适用垂直非均匀各向异性介质。精度的提高使能够用4分量地震资料计算各向异性参数。为此提出了两种工作流程：双扫描和单扫描流程。理论数据和实际数据的应用表明这两种流程得出的结果其精度相似，但是单扫描流程比双扫描更有效。 相似文献
20.
In this paper, the seismicity indexes of global earthquakesM ≥ 6 during 1964–1983 were calculated, using data of ISC and USGS. The authors suggested a method suitable to make a set of
regression formulas betweenm
bandM
s. Calculation showed that the level of global seismicity of shallow earthquakes during the years 1964–1965, 1968, 1971, 1975–1976
was higher than normal, especially the peak for the years 1975–1976 was more conspicuous. The year 1984 took the place of
the year 1954 in the 20th century as the year of lowest global shallow focus seismicity. According to the actual value ofA(b) calculated, the level of deep focus seismicity reached the highest point in 1971 and dropped to the lowest point in 1977.
In the time interval of 1977–1983 the global shallow focus seismicity decreased continuously whereas the deep focus seismicity
increased with fluctuations. 相似文献