scholarly journals Deformation Analysis of Granular Soils under Dynamic Compaction Based on Stochastic Medium Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Jifang Du ◽  
Shuaifeng Wu ◽  
Sen Hou ◽  
Yingqi Wei
Keyword(s):  
Computational Model ◽  
Back Analysis ◽  
Dynamic Compaction ◽  
Deformation Analysis ◽  
Published Data ◽  
Granular Soils ◽  
Stochastic Medium ◽  
Soil System ◽  
Medium Theory ◽  
Granular Fill

Dynamic compaction (DC) is widely used to improve the mechanical properties of soils and other granular fill material upon which foundations or other structures are to be built. To calculate the inner deformation induced by DC, a computational model based on stochastic medium theory was developed to deduce the amount of deformation in the fill from the geometry of the DC crater. For this model, the tamper-soil system was simplified to an axisymmetric geometry and the probability of any unit of material below the crater being deformed can be calculated. Subsequently, the deformation at any point can be obtained by integration. Input parameters for the model were established by back analysis using the results from a DC field test and published data. Comparing the model results to results from actual and simulated DC programs shows that the computational model is useful for calculating deformation induced by DC without the need to consider the constitutive model of the soil.

scholarly journals Ground Movement Analysis Based on Stochastic Medium Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Meng Fei ◽  
Wu Li-chun ◽  
Zhang Jia-sheng ◽  
Deng Guo-dong ◽  
Ni Zhi-hui
Keyword(s):  
Distribution Function ◽  
Back Analysis ◽  
Movement Analysis ◽  
Measured Data ◽  
Ground Movement ◽  
Pile Driving ◽  
Normal Distribution Function ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Vertical Ground

In order to calculate the ground movement induced by displacement piles driven into horizontal layered strata, an axisymmetric model was built and then the vertical and horizontal ground movement functions were deduced using stochastic medium theory. Results show that the vertical ground movement obeys normal distribution function, while the horizontal ground movement is an exponential function. Utilizing field measured data, parameters of these functions can be obtained by back analysis, and an example was employed to verify this model. Result shows that stochastic medium theory is suitable for calculating the ground movement in pile driving, and there is no need to consider the constitutive model of soil or contact between pile and soil. This method is applicable in practice.

Analysis of Ground Movement in Pile Driving Based on Stochastic Medium Theory

2013 ◽  
Vol 438-439 ◽  
pp. 1404-1408 ◽  
Author(s):  
Fei Meng ◽  
Jia Sheng Zhang ◽  
Hui Ying Liu
Keyword(s):  
Axisymmetric Problem ◽  
Back Analysis ◽  
Measured Data ◽  
Ground Movement ◽  
Pile Driving ◽  
Normal Distribution Function ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Vertical Ground ◽  
Soil Interface

In order to calculate the ground movement induced by displacement piles driven into horizontal layered soil, it is simplified to an axisymmetric problem. Then the vertical and horizontal ground movement functions were deduced based on stochastic medium theory. The vertical ground movement is a normal distribution function, while the horizontal ground movement is an exponential function. Utilizing field measured data, parameters of these functions can be obtained by back analysis. The example indicates that the stochastic medium theory is suitable for calculating the ground movement in pile driving, and there is no need to consider the constitutive model of soil or contact model of pile-soil interface in calculation. This method is fairly applicable in practice, and can provide a reference for related research.

scholarly journals Simulation of P2X-mediated calcium signaling in microglia

2018 ◽  
Author(s):  
Ben Chun ◽  
Bradley D. Stewart ◽  
Darin Vaughan ◽  
Adam D. Bachstetter ◽  
Peter M. Kekenes-Huskey
Keyword(s):  
Computational Model ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Quantitative Model ◽  
Published Data ◽  
Transcriptional Responses ◽  
Extracellular Adenosine ◽  
Wide Range ◽  
Intracellular Ca

AbstractMicroglia function is orchestrated through highly-coupled signaling pathways that depend on calcium (Ca2+). In response to extracellular adenosine triphosphate (ATP), transient increases in intracellular Ca2+ driven through the activation of purinergic receptors, P2X and P2Y, are sufficient to promote cytokine synthesis and potentially their release. While steps comprising the pathways bridging purinergic receptor activation with transcriptional responses have been probed in great detail, a quantitative model for how these steps collectively control cytokine production has not been established. Here we developed a minimal computational model that quantitatively links extracellular stimulation of two prominent ionotropic puriner-gic receptors, P2X4 and P2X7, with the graded production of a gene product, namely the tumor necrosis factor α (TNFα) cytokine. In addition to Ca2+ handling mechanisms common to eukaryotic cells, our model includes microglia-specific processes including ATP-dependent P2X4 and P2X7 activation, activation of NFAT transcription factors, and TNFα production. Parameters for this model were optimized to reproduce published data for these processes, where available. With this model, we determined the propensity for TNFα production in microglia, subject to a wide range of ATP exposure amplitudes, frequencies and durations that the cells could encounter in vivo. Furthermore, we have investigated the extent to which modulation of the signal transduction pathways influence TNFα production. Our key findings are that TNFα production via P2X4 is maximized at low ATP when subject to high frequency ATP stimulation, whereas P2X7 contributes most significantly at millimolar ATPranges. Given that Ca2+ homeostasis in microglia is profoundly important to its function, this computational model provides a quantitative framework to explore hypotheses pertaining to microglial physiology.

scholarly journals Integrated experimental-computational analysis of a liver-islet microphysiological system for human-centric diabetes research

2021 ◽  
Author(s):  
Belén Casas ◽  
Liisa Vilén ◽  
Sophie Bauer ◽  
Kajsa Kanebratt ◽  
Charlotte Wennberg Huldt ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Computational Model ◽  
In Silico ◽  
Experimental Results ◽  
Published Data ◽  
Diabetes Research ◽  
Glucose Response ◽  
High Blood Glucose

Microphysiological systems (MPS) are powerful tools for emulating human physiology and replicating disease progression in vitro. MPS could be better predictors of human outcome than current animal models, but mechanistic interpretation and in vivo extrapolation of the experimental results remain significant challenges. Here, we address these challenges using an integrated experimental-computational approach. This approach allows for in silico representation and predictions of glucose metabolism in a previously reported MPS with two organ compartments (liver and pancreas) connected in a closed loop with circulating medium. We developed a computational model describing glucose metabolism over 15 days of culture in the MPS. The model was calibrated on an experiment-specific basis using data from seven experiments, where single-liver or liver-islet cultures were exposed to both normal and hyperglycemic conditions resembling high blood glucose levels in diabetes. The calibrated models reproduced the fast (i.e. hourly) variations in glucose and insulin observed in the MPS experiments, as well as the long-term (i.e. over weeks) decline in both glucose tolerance and insulin secretion. We also investigated the behavior of the system under hypoglycemia by simulating this condition in silico, and the model could correctly predict the glucose and insulin responses measured in new MPS experiments. Last, we used the computational model to translate the experimental results to humans, showing good agreement with published data of the glucose response to a meal in healthy subjects. The integrated experimental-computational framework opens new avenues for future investigations toward disease mechanisms and the development of new therapies for metabolic disorders.

scholarly journals A New Modified Peck Formula for Predicting the Surface Settlement Based on Stochastic Medium Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Zhanping Song ◽  
Xiaoxu Tian ◽  
Yuwei Zhang
Keyword(s):  
Friction Angle ◽  
Surface Settlement ◽  
Calculation Error ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Comparison Results ◽  
Calculation Process ◽  
The Difference ◽  
Shallow Buried Tunnel ◽  
Prediction Approach

Peck method and stochastic medium method are the two most commonly used methods to estimate surface settlement caused by tunnel excavation. However, the Peck method was not suitable for a shallow-buried tunnel, and the calculation process of the stochastic medium theory was complicated. To solve this problem, in this paper, a simple and accurate prediction approach for surface settlement was obtained by improving the Peck method based on the basic idea of stochastic medium theory. In detail, the over-excavation area of the tunnel was divided into n independent units, and the surface settlement caused by the collapse of each unit was calculated, respectively. Then, the total surface settlement can be obtained by superimposing surface settlement induced by each unit. Taking the shallow-buried section of Mulingguan tunnel entrance as a case, the surface settlement calculated by the modified Peck formula and original Peck formula was compared with the observed data, respectively. The comparison results indicated that the surface settlement calculated by the modified Peck formula is closer to the observed data than that calculated by the original Peck formula in the calculation process of surface settlement of shallow-buried tunnel. The table of recommendation for the number of units can be obtained by a discussion of reasonable n values. Finally, the difference between the original Peck formula and the modified Peck formula was analysed, and the results showed that the change rule of the surface settlement is consistent under the tunnel depth, internal friction angle, and ground loss of the tunnel. However, the calculation error of the surface settlements calculated by the original Peck formula is more significant than that calculated by modified Peck formula under the tunnel diameter ratio being less than 1.75. The modified Peck formula is more suitable for calculating the surface settlement under internal angle friction being less than 20° or greater than 40°. The research results expand the scope of application of the original Peck formula and enrich the calculation approach of surface settlement induced by underground excavation in tunnel construction.

scholarly journals Analysis of the Design of a Poppet Valve by Transitory Simulation

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 889 ◽  
Author(s):  
Ivan Gomez ◽  
Andrés Gonzalez-Mancera ◽  
Brittany Newell ◽  
Jose Garcia-Bravo
Keyword(s):  
Computational Model ◽  
Dynamic Behavior ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Published Data ◽  
Minimal Effect ◽  
High Frequencies ◽  
Poppet Valve ◽  
Dimensional Parameters ◽  
Volume Method

This article contains the results and analysis of the dynamic behavior of a poppet valve through CFD simulation. A computational model based on the finite volume method was developed to characterize the flow at the interior of the valve while it is moving. The model was validated using published data from the valve manufacturer. This data was in accordance with the experimental model. The model was used to predict the behavior of the device as it is operated at high frequencies. Non-dimensional parameters for generalizing and analyzing the effects of the properties of the fluid were used. It was found that it is possible to enhance the dynamic behavior of the valve by altering the viscosity of the working fluid. Finally, using the generated model, the influence of the angle of the poppet was analyzed. It was found that angle has a minimal effect on pressure. However, flow forces increase as angle decreases. Therefore, reducing poppet angle is undesirable because it increases power requirements for valve actuation.

scholarly journals A new laboratory apparatus for studying dynamic compaction grouting into granular soils

2013 ◽  
Vol 53 (3) ◽  
pp. 462-468 ◽  
Author(s):  
S.Y. Wang ◽  
D.H. Chan ◽  
K.C. Lam ◽  
S.K.A. Au
Keyword(s):  
Dynamic Compaction ◽  
Granular Soils ◽  
Laboratory Apparatus ◽  
Compaction Grouting

Influence Mechanism of Isolation Layer to Granular Media Flow

2012 ◽  
Vol 256-259 ◽  
pp. 2514-2518
Author(s):  
Yun Xiang Liu ◽  
Qing Fa Chen ◽  
Hong Qi Chen
Keyword(s):  
Granular Media ◽  
Working Condition ◽  
Underground Mining ◽  
Particle Flow Code ◽  
Radius Of Curvature ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Isolation Layer ◽  
Influence Mechanism ◽  
Shrinkage Method

By using particle flow code (PFC2D), influence mechanism of isolation layer to granular media flow was studied by simulating two ore-drawing modes of filling mining method (working condition Ⅰ) and synchronous filling shrinkage method(working condition Ⅱ). After analyzed simulation results, some laws were gotten: (1) by the fitting process conducted on released volume and height, it is found that the relationship of released volume and height was power equation, which is same as the stochastic medium theory for ore-drawing; (2) The released volume, the size in most width of loosing body and the location of working condition Ⅱ was both bigger than those of working condition Ⅰ; (3) the radius of curvature of drawn-funnel of working conditionⅡ was bigger than those of working conditionⅠ, but the volume of residual ore was opposite. Analysis shows that the isolation layer reduced the contact force in ore drawing regional, made the porosity bigger, so as to improve liquidity. The results provide a theoretical reference for the changes in underground mining techniques and ore-drawing control.

Sign in / Sign up

Export Citation Format

Share Document