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1.
Assuming a radially stratified Newtonian mantle in a steady-state approximation, we demonstrate that the permeability of a viscosity interface at 660-km depth strongly depends on the wavelength of buoyancy forces driving the flow. The flow induced by long-wavelength loads penetrates through the boundary freely even if the viscosity increases by two orders. In contrast, the boundary is practically impermeable for short-wavelength loads located in the upper mantle. Thus, a stepwise increase of viscosity is a significant obstacle for small descending features in the upper mantle, but huge upper mantle downwellings, or upwellings formed in the-lower mantle can overcome it easily. This indicates that certain care is necessary in interpreting the seismic structure of the mantle by means of flow models. The global tomographic image includes only the first few degrees of the harmonic series and, consequently, its interpretation in terms of a present-day flow field results in a predominantly whole-mantle circulation even for extreme viscosity contrasts. 相似文献
2.
We present the preliminary results of axisymmetric numerical simulations of thermal convection in the mantle with a phase transition boundary at 660 km depth and a viscosity interface at 1000 km depth. The results, obtained for Ra = 2 × 10
6
, are compared with the case when both the phase and the viscosity boundaries are located at the same depth of 660 km. 相似文献
3.
The shear viscosity of a suspension of deformable bubbles dispersed within a Newtonian fluid is calculated as a function of the shear rate and strain. The relative importance of bubble deformation in the suspension is characterized by the capillary number (Ca), which represents the ratio of viscous and surface tension stresses. For small Ca, bubbles remain nearly spherical, and for sufficiently large strains the viscosity of suspension is greater than that of the suspending fluid, i.e. the relative viscosity is greater than 1. If Ca>O(1) the relative viscosity is less than one. In the limit that Ca→∞ (surface tension is dynamically negligible), numerical calculations for a suspension of spherical bubbles agree well with the experimental measurements of Lejeune et al. (1999, Rheology of bubble-bearing magmas. Earth Planet. Sci. Lett., vol. 166, pp. 71–84). In general, bubbles have a modest effect on the relative viscosity, with viscosity changing by less than a factor of about 3 for volume fractions up to 50%. 相似文献
4.
Statistical damage detection method for frame structures using a confidence interval 总被引:1,自引:0,他引:1
<正>A novel damage detection method is applied to a 3-story frame structure,to obtain statistical quantification control criterion of the existence,location and identification of damage.The mean,standard deviation,and exponentially weighted moving average(EWMA) are applied to detect damage information according to statistical process control(SPC) theory.It is concluded that the detection is insignificant with the mean and EWMA because the structural response is not independent and is not a normal distribution.On the other hand,the damage information is detected well with the standard deviation because the influence of the data distribution is not pronounced with this parameter.A suitable moderate confidence level is explored for more significant damage location and quantification detection,and the impact of noise is investigated to illustrate the robustness of the method. 相似文献
5.
R/SanalysisofearthquaketimeintervalChang-HaiLIU;(刘长海)Yi-GaoLIU;(刘义高)andJunZHANG;(张军)(SeismologicalBureauofAnhuiProvince,Hefei... 相似文献
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8.
An infinite horizontal layer, with vertically stratified temperature and solute concentration, is considered in the case where the viscosity is exponentially dependent on temperature, and the Prandtl number is infinite. Its linear stability is investigated when the destabilizing thermal gradient acts against a stabilizing solute gradient. The analysis is performed using horizontal Fourier and vertical Chebyshev polynomial expansions. For the constant viscosity case, the laws well established in the free boundary configuration are seen to be directly suitable for the rigid one. In the variable viscosity case, characterised by a given viscosity contrast c, the scaling laws with c are settled extrapolating to the double diffusive situation the approach initiated by Stengel et al. (1982). In contrast with the constant viscosity case, the critical wave number is found to be strongly dependent on the solutal Rayleigh number in the marginal oscillatory obtained at large contrast values. 相似文献
9.
汶川Ms8.0地震发生在青藏高原东缘NE向龙门山断裂带上,造成以映秀、北川为中心的长达300km的同震地表破裂带.初步研究认为,龙门山断裂带大震复发属于特征地震模式.本文在考虑地形差异影响下,用有限元数值模拟方法对汶川地震的大震复发周期进行研究.初步结果表明:龙门山断裂带大震复发周期为3908~4482a,该结果与古地震、断层滑动法、地震矩率、GPS数据确定等给出的结果具有较好的一致性,为龙门山断裂带的地震活动性及地震危险性研究提供重要的定量依据. 相似文献
10.
Ozan Eskikaya Pinar Belibagli Raouf Bouchareb Zelal Isik Nadir Dizge 《洁净——土壤、空气、水》2024,52(3):2300083
Waste motor oil (WMO), which has no stable form or structure, causes major environmental problems and damage to the ecosystem once it is disposed to the environment. Because of the high toxicity of contents in such effluent, it must be treated before being discharged into the receiving environment. In recent years, the valorization and the use of waste materials to remove toxic pollutants is of great importance to researchers and diverse industries. In this study, the usability of waste welding powder (WWP) as an adsorbent for waste oil removal was investigated. For this purpose, investigating the usability of material, which is generated as industrial waste, in wastewater treatment will lead to the evaluation of waste. The effects of temperature, pH, WWP amount, and initial WMO amount were investigated. According to the adsorption studies, 1 g WWP/L of the processed adsorbent was able to effectively remove 95.05% of WMO (100 mg) at a pH of 2 at 30°C. Stereo microscopy images showed a large amount of oil adsorbed on the WWP surface. The different WWP properties were determined by adsorption isotherm (Harkins–Jura), kinetic (pseudo-second order), and thermodynamic (ΔG: −5.1 kJ mol–1) experiments. It is thought that WWP, which is a low-cost and waste material, can be used as a promising adsorbent in WMO removal. 相似文献
11.
Viscosity measurements of subliquidus magmas: Alkali olivine basalt from the Higashi-Matsuura district, Southwest Japan 总被引:3,自引:0,他引:3
We carried out viscosity measurements and sampling of a crystal suspension derived from alkali olivine basalt from the Matsuura district, SW Japan, at subliquidus temperatures from 1230 °C to 1140 °C under 1 atm with NNO oxygen buffered conditions. Viscosity increased from 31 to 1235 Pa s with a decrease in temperature from 1230 to 1140 °C. On cooling, olivine first appeared at 1210 °C, followed by plagioclase at 1170 °C. The crystal content of the sample attained 31 vol.% at 1140 °C (plagioclase 22%, olivine 9%). Non-Newtonian behaviors, including thixotropy and shear thinning, were pronounced in the presence of tabular plagioclase crystals. The cause of such behavior is discussed in relation to shear-induced changes in melt–crystal textures. Relative viscosities, ηr (= ηs / ηm, where ηs and ηm are the viscosities of the suspension and the melt, respectively), were obtained by calculating melt viscosities from the melt composition and temperature at 1 atm using the equation proposed by Giordano and Dingwell [Giordano, D., Dingwell, D.B., 2003. Non-Arrhenian multicomponent melt viscosity: a model. Earth and Planetary Science Letters, 208, 337–349.]. The obtained relative viscosities are generally consistent with the Einstein–Roscoe relation, which represents ηr for suspensions that contain equant and equigranular crystals, even though the crystal suspension analyzed in the present experiments contained tabular plagioclase and granular olivine of various grain sizes. This consistency is attributed to the fact that the effect of crystal shape was counterbalanced by the effect of the dispersion of crystal size. The applicability of the Einstein–Roscoe equation with respect to crystal shape is discussed on the basis of the present experimental results. Our experiments and those of Sato [Sato, H., 2005. Viscosity measurement of subliquidus magmas: 1707 basalt of Fuji volcano. Journal of Mineralogical and Petrological Sciences, 100, 133–142.] show that the relationship between relative viscosity and crystal fraction is consistent with the Einstein–Roscoe relationship for axial ratios that are smaller than the critical value of 4–6.5, but discrepancies occur for higher ratios. 相似文献
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On the basis of fault’s dynamic model of Knopoffet al. (1973), this paper has finally obtained a simple approximate formula to be able to estimate the recurrence time intervalT
R
of earthquake on strike-slip fault. Preliminary result holds thatμ andδ
s
— δ
f
have not much effect onT
R
. Leta is the ratio of the coseismic displacementD
s
to the total displacementD
t
in whole event course, i.e.,a =D
s
/D
t
, thena = 1/3 may represent the standard theoretical state in whichT
R
is independent onμ andδ
s
— δ
f
. At this time,T
R
is the arithmetic average ofs
0/v andkd/β, wheres
0 is the long-term preseismic accumulated slippage,v is fault’s average displacement rate,d is the fracture length on the fault of seismic focal region andβ is shear wave velocity. In addition,k =υ
0/aυ, whereυ
0 is the initial fracture velocity of actual structure at the coseismic instant.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 187–194, 1992.
This paper is a part of contracted item of State Seismological Bureau — Tectonic Physical Study of Earthquake Recurrence Period
and Characteristic Magnitude. 相似文献
14.
An incremental Knox test for the determination of the serial interval between successive cases of an infectious disease 总被引:1,自引:0,他引:1
An estimate of the interval between successive infections is essential for surveillance, control, and modeling of infectious
diseases. This paper proposes a method for determining the serial interval when the location and time of onset of illness
are known. The theoretical underpinning of this method is the intrinsically spatial nature of disease transmission. Successive
infections tend to be closer than unrelated cases of disease and, therefore, exhibit spatial clustering. An incremental Knox
type analysis of cases is introduced. Cases occurring at a range of time intervals are examined to determine the serial interval.
The significance of clustering is determined using a permutation approach under the null hypothesis of space-time independence.
The power of this method is evaluated using an individual level, spatially explicit epidemic simulation. The time increment
Knox test is robust to multiple introductions and incomplete sampling. Finally, the increment Knox statistic is used to analyze
an outbreak of dengue fever in the city of Florida, Puerto Rico during 1991. Results indicate that the likely interval between
successive cases during this outbreak is at least 18–19 days. 相似文献
15.
基于最大熵原理,得到地震时间间隔和地震震级的概率分布函数。根据时间间隔分布,得到地震发震概率,当概率上升达到警界值时,可对云南5级以上中强地震做出预测。6个月以内中短期预测对应率为91%;3个月以内,短临期预测对应率为73%。根据震级分布,得到用最大熵原理求出的地震理论发生次数,理论发震次数与实际较为接近。用最大熵原理求出了云南不同地区不同震级档次5级以上中强地震的复发周期。分析认为,云南7级以上大震危险性在逐步逼近,西部危险性高于东部。 相似文献
16.
17.
The slip rate and strong earthquake recurrence interval on the Qianning-Kangding segment of the Xianshuihe fault zone 总被引:2,自引:0,他引:2
IntroductionLocated in the western part of Sichuan Province, China, the Xianshuihe fault zone is a notable strong earthquake zone in the eastern Tibetan Plateau. At its northwestern end, the Xianshuihe fault zone overlaps the Ganzi-Yushu fault in a left-stepping pattern. The fault zone extends southeastwards through Luhuo, Daofu, Kangding, and Moxi and disappears near Shimian, with a total length of 400 km. The fault trends N40(-50°W in the north, and N20(-30°W to the south of Kangdi… 相似文献
18.
Planning of municipal solid waste management systems under dual uncertainties: a hybrid interval stochastic programming approach 总被引:3,自引:3,他引:0
G. H. Cheng G. H. Huang Y. P. Li M. F. Cao Y. R. Fan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(6):707-720
In this study, a random-boundary-interval linear programming (RBILP) method is developed and applied to the planning of municipal
solid waste (MSW) management under dual uncertainties. In the RBILP model, uncertain inputs presented as interval numbers
can be directly communicated into the optimization process; besides, intervals with uncertain lower and upper bounds can be
handled through introducing the concept of random boundary interval. Consequently, robustness of the optimization process can be enhanced. To handle uncertainties with such complex presentations,
an integrated chance-constrained programming and interval-parameter linear programming approach (ICCP) is proposed. ICCP can
help analyze the reliability of satisfying (or risk of violating) system constraints under uncertainty. The applicability
of the proposed RBILP and ICCP approach is validated through a case study of MSW management. Violations for capacity constraints
are allowed under a range of significant levels. Interval solutions associated with different risk levels of constraint violation
are obtained. They can be used for generating decision alternatives and thus helping waste managers to identify desired policies
under various environmental, economic, and system-reliability constraints. 相似文献
19.
Ali A. Nowroozi 《Pure and Applied Geophysics》1990,133(1):103-115
In reflection surveys and velocity analysis, calculations of interval velocities and layer-thicknesses of a multilayered horizontal structure are often based on Dix's equation which requires the travel times at zero offsets and a prior estimate of the root mean squared velocities.In this paper a method is presented which requires only the reflection travel-time data. A set of equations are derived which relate the interval velocity and thickness of a layer to the reflection travel time from the top and the bottom of that layer, the offset distances and the ray parameter. It is shown that the difference of the offset distances and the difference of the picked travel times of any reflected rays with the same value of ray parameter from the top and the bottom of a horizontal layer can be used to calculate the interval velocity and thickness of that layer. 相似文献
20.
Wide-angle reflections are now routinely recorded in high resolution explosion seismics to study the crustal structure. Use of Dix's hyperbolic approximation to the nonhyperbolic wide-angle reflection travel times causes major errors in the determination of interval velocities and layer thicknesses of a stack of horizontal velocity layers. Here we propose a layer stripping method to directly calculate the interval velocities and layer thicknesses in a vertically heterogeneous earth from the strong and reliable wide-angle reflected events. Synthetic reflection travel times, at wide-angle range, for a given velocity model, contaminated by some random errors, have been used to demonstrate the reliability of the algorithms to determine the interval velocities and thicknesses of various layers. The method has also been tested on two field examples along two deep seismic sounding (DSS) profiles with well identified wide-angle reflection travel times, which illustrates the practical feasibility of the proposed method. 相似文献