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351.
Pelin Tohumcu Özener Kutay Özaydın Mehmet M. Berilgen 《Bulletin of Earthquake Engineering》2009,7(1):199-219
This paper presents the results of shaking table model tests which were carried out to investigate the pore water pressure
generation and related liquefaction mechanism in layered sand deposits. The experiments were performed on uniform sand columns,
silt interlayered sand columns and two layered sand columns deposited at various relative densities and subjected to different
input excitations. During the experiments excess pore water pressures were measured by pore pressure transducers installed
at three different depths and, surface settlements and thickness of water film developed under less permeable inclusions were
measured by a digital camera. The experimental results are discussed and compared to demonstrate the effects of relative density,
input acceleration and presence of a silt seam on the generation of excess pore water pressure in sand deposits subjected
to dynamic loading. The results showed that the presence of a less permeable silt interlayer within the sand deposit and existence
of a loose sand layer underlying dense sand deposits can have significant effect on the pore water pressure generation mechanism. 相似文献
352.
An important challenge in theoretical ecology is to find good coarse-grained representations of complex food webs. Here, we
use the approach of generalized modeling to show that it may be possible to formulate a coarse-graining algorithm that conserves
the local dynamics of the model exactly. We show examples of food webs with a different number of species that have exactly
identical local bifurcation diagrams. Based on these observations, we formulate a conjecture governing which populations of
complex food webs can be grouped together into a single variable without changing the local dynamics. As an illustration,
we use this conjecture to show that chaotic regions generically exist in the parameter space of a class of food webs with
more than three trophic levels. While our conjecture is at present only applicable to relatively special cases, we believe
that its applicability could be greatly extended if a more sophisticated mapping of parameters were used in the model reduction. 相似文献
353.
The ecological tidal model simulates the cycling of carbon, nitrogen, phosphate, and silicate and describes the tidal, diurnal,
and annual dynamics of the back barrier area of the island Spiekeroog in the German Bight. The region is characterized by
strong tidal currents and extensive tidal flats. It is strongly influenced by the conditions in the southern part of the German
Bight. This model study investigates the dependence of the model behavior on the boundary conditions and the forcing. The
effect of short- and long-term sea level rise on nutrient and plankton dynamics is analyzed. As the model is set up as semi-Lagrangian
with only a coarse approximation of the hydrodynamics, the seasonal and intratidal variability in the biogeochemical cycling
can only be reproduced qualitatively. By varying the boundary conditions, the intrinsic dynamics of the back barrier area
can be separated from boundary condition effects. This study shows that any agreement between model results and field data
cannot be expected without correct boundary conditions. The seasonal variability is of major importance, while higher-frequency
variability only plays a minor role. 相似文献
354.
基于SD和CA的城镇土地扩展模拟模型——以江苏省南通地区为例 总被引:7,自引:1,他引:6
充分利用系统动力学模型(System Dynamics,SD)在情景模拟和宏观因素反映上的优势和元胞自动机模型(Cellular Automata,CA)在微观土地利用空间格局反映上的优势,构建一个耦合SD和CA的城镇土地扩展模拟模型,并以江苏省南通地区为例,对模型的实证应用做了进一步的验证。结果表明,这种耦合模型不仅能够对研究区域未来城镇土地扩展数量给予一个比较好的预测,而且还对其空间分布效果做了一定精度上的模拟,这使得城市规划在土地利用预测方面有一个相对科学的依据。 相似文献
355.
岩溶水作用下填石路基稳定性模型试验研究 总被引:2,自引:2,他引:0
以广西水南高速为工程依托点,通过大型岩溶塌陷物理模型试验室,针对岩溶区填石路基中不同岩溶形态的处置方式,模拟研究岩溶水对填石路基的稳定性问题。试验中,重点研究了四种结构: 填石级配型、(片石+ 级配碎石+ 土工布+填石)型、反滤层型、(土+ 填石)型,它们分别对应岩溶水对填石路基侵蚀问题及填石路基的稳定性问题,漏斗、落水洞的处理及土工布防止细粒土流失引起路基变形问题,溶洞填充物的流失问题,岩溶水对粘土路基潜蚀问题及石牙地基的处理。试验结果表明,地下水位变化的瞬时速度对填石路基的稳定性具有重要意义,不同的处置方法在抵抗地下水冲刷方面有显著区别。 相似文献
356.
以辽宁原油消耗为研究对象,综合运用EKC曲线模型和IPAT模型对辽宁石油资源消耗变化及影响因子进行了模拟分析。结果表明:辽宁处于石油资源消耗的高增长阶段,其极大程度是受经济发展所驱动的。科学技术进步对石油资源消耗有一定程度上的减缓作用,而人口的平稳增长对石油资源退化没有明显的影响;一段时期内,辽宁石油资源消耗还将呈现增长趋势。将2种模型模拟分析方法综合使用,可找出能源可持续性变化的科学依据,为经济发展和环境管理决策提供参考。 相似文献
357.
This work presents models of the vertical distribution and flux of phytoplankton aggregates, including changes with time in
the distribution of aggregate sizes and sinking speeds. The distribution of sizes is described by two parameters, the mass
and number of aggregates, which greatly reduces the computational cost of the models. Simple experiments demonstrate the effects
of aggregation on the timing and depth distribution of primary production and export. A more detailed ecological model is
applied to sites in the Arabian Sea; it demonstrates that aggregation can be important for deep sedimentation even when its
effect on surface concentrations is small, and it presents the difference in timing between settlement of aggregates and fecal
pellets. 相似文献
358.
经济预测模型在土地规划中的应用与分析 总被引:4,自引:0,他引:4
主要介绍土地规划时需用到的几种预测模型 ,具体阐述了几种模型的原理 ,并以抚州地区的总人口历史数据为例 ,进行实际的预测与分析 ,从而总结各种模型的优缺点 ,选择最合适的土地规划预测模型。 相似文献
359.
360.
H ,L i ,Mg2 / Cl-- H2 O四元体系 0°C,2 0°C,4 0°C的溶解度预测中需要大量参数 ,而这些参数的获得 ,依赖于盐酸 -碱金属氯化物 -水三元体系和 HCl- L i Cl- Mg Cl2 - H2 O四元体系的热力学性质。总结了近 50年来国内外对上述体系的热力学性质的研究 ,为 H ,L i ,Mg2 / Cl-- H2 O四元体系 0°C,2 0°C,4 0°C的溶解度预测奠定基础 ,同时为 Pitzer模型增添更合理的参数。 相似文献