Effect of Drying on Viscoelasticity and Permeability of Gel

1994 ◽  
Vol 346 ◽  
Author(s):  
George W. Scherer
Keyword(s):  
Elastic Modulus ◽  
Silica Gel ◽  
Exponential Function ◽  
Power Law ◽  
Relaxation Function ◽  
Relaxation Behavior ◽  
Viscoelastic Relaxation ◽  
Acid Base ◽  
Stretched Exponential ◽  
Beam Bending

ABSTRACTThe beam-bending method was used to measure the effect of partial drying on the viscoelastic relaxation behavior and permeability of a two-step acid-base catalyzed silica gel. Both the elastic modulus (E) and the permeability (D) showed a power-law dependence on density (ρ): E ～ ρm, m ≈ 3.0; D ～ ρ-n, n ≈ 2.5. The viscosity of the network rose from ～1011 to ～1013 Pa·s, and was strongly dependent on age as well as density of the gel. The viscoelastic relaxation function was well described by the stretched exponential function with an exponent of 0.3–0.5.

Role of Cytoskeletal Components in Stress-Relaxation Behavior of Adherent Vascular Smooth Muscle Cells

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Jason D. Hemmer ◽  
Jiro Nagatomi ◽  
Scott T. Wood ◽  
Alexey A. Vertegel ◽  
Delphine Dean ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Stress Relaxation ◽  
Power Law ◽  
Relaxation Function ◽  
Cytochalasin D ◽  
Relaxation Behavior ◽  
Power Law Model ◽  
Stress Relaxation Behavior ◽  
Relaxation Experiments

A number of recent studies have demonstrated the effectiveness of atomic force microscopy (AFM) for characterization of cellular stress-relaxation behavior. However, this technique’s recent development creates considerable need for exploration of appropriate mechanical models for analysis of the resultant data and of the roles of various cytoskeletal components responsible for governing stress-relaxation behavior. The viscoelastic properties of vascular smooth muscle cells (VSMCs) are of particular interest due to their role in the development of vascular diseases, including atherosclerosis and restenosis. Various cytoskeletal agents, including cytochalasin D, jasplakinolide, paclitaxel, and nocodazole, were used to alter the cytoskeletal architecture of the VSMCs. Stress-relaxation experiments were performed on the VSMCs using AFM. The quasilinear viscoelastic (QLV) reduced-relaxation function, as well as a simple power-law model, and the standard linear solid (SLS) model, were fitted to the resultant stress-relaxation data. Actin depolymerization via cytochalasin D resulted in significant increases in both rate of relaxation and percentage of relaxation; actin stabilization via jasplakinolide did not affect stress-relaxation behavior. Microtubule depolymerization via nocodazole resulted in nonsignificant increases in rate and percentage of relaxation, while microtubule stabilization via paclitaxel caused significant decreases in both rate and percentage of relaxation. Both the QLV reduced-relaxation function and the power-law model provided excellent fits to the data (R2=0.98), while the SLS model was less adequate (R2=0.91). Data from the current study indicate the important role of not only actin, but also microtubules, in governing VSMC viscoelastic behavior. Excellent fits to the data show potential for future use of both the QLV reduced-relaxation function and power-law models in conjunction with AFM stress-relaxation experiments.

Conductivity, Dielectric and Modulus study of NH4PF6 based Zwitterionic polymer electrolyte

2020 ◽  
Vol 13 ◽  
Author(s):  
Manindra Kumar ◽  
Neelabh Srivastava
Keyword(s):  
Polymer Electrolyte ◽  
Power Law ◽  
Loss Tangent ◽  
Electric Modulus ◽  
Relaxation Behavior ◽  
Conductivity Data ◽  
Frequency Range ◽  
Zwitterionic Polymer ◽  
Power Law Equation ◽  
Jonscher’S Power Law

Background and Objective: Zwitterionic polymer electrolyte has been successfully synthesized using NH4PF6 salt. The conductivity of the synthesized polymer membrane is found to be of the order of 10-3Scm-1. Dielectric and Modulus properties of the polymer electrolyte have also been studied which showed well relaxation peaks with both temperature and salt concentrations. Result: This is well depicted with the loss tangent curve. Debye type relaxation behavior has observed from the electric modulus. Conclusion: Frequency dependent conductivity data (fitted with Jonscher's power law equation) confirmed the presence of NCL/SLPL type behavior in the studied frequency range.

POWER LAW AND STRETCHED EXPONENTIAL EFFECTS OF EXTREME EVENTS IN CHINESE STOCK MARKETS

2010 ◽  
Vol 09 (02) ◽  
pp. 203-217 ◽  
Author(s):  
XIAOJUN ZHAO ◽  
PENGJIAN SHANG ◽  
YULEI PANG
Keyword(s):  
Correlation Analysis ◽  
Power Law ◽  
Extreme Events ◽  
Stock Markets ◽  
Cross Correlation ◽  
Extreme Values ◽  
Cumulative Distribution ◽  
Stretched Exponential ◽  
Cross Correlation Analysis ◽  
Chinese Stock Markets

This paper reports the statistics of extreme values and positions of extreme events in Chinese stock markets. An extreme event is defined as the event exceeding a certain threshold of normalized logarithmic return. Extreme values follow a piecewise function or a power law distribution determined by the threshold due to a crossover. Extreme positions are studied by return intervals of extreme events, and it is found that return intervals yield a stretched exponential function. According to correlation analysis, extreme values and return intervals are weakly correlated and the correlation decreases with increasing threshold. No long-term cross-correlation exists by using the detrended cross-correlation analysis (DCCA) method. We successfully introduce a modification specific to the correlation and derive the joint cumulative distribution of extreme values and return intervals at 95% confidence level.

scholarly journals An Investigation of Stretched Exponential Function in Quantifying Long-Term Memory of Extreme Events Based on Artificial Data following Lévy Stable Distribution

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
HongGuang Sun ◽  
Lin Yuan ◽  
Yong Zhang ◽  
Nicholas Privitera
Keyword(s):  
Exponential Distribution ◽  
Exponential Function ◽  
Extreme Events ◽  
Stable Distribution ◽  
Wide Spectrum ◽  
Long Term Memory ◽  
Term Memory ◽  
Stretched Exponential ◽  
Stretched Exponential Distribution

Extreme events, which are usually characterized by generalized extreme value (GEV) models, can exhibit long-term memory, whose impact needs to be quantified. It was known that extreme recurrence intervals can better characterize the significant influence of long-term memory than using the GEV model. Our statistical analyses based on time series datasets following the Lévy stable distribution confirm that the stretched exponential distribution can describe a wide spectrum of memory behavior transition from exponentially distributed intervals (without memory) to power-law distributed ones (with strong memory or fractal scaling property), extending the previous evaluation of the stretched exponential function using Gaussian/exponential distributed random data. Further deviation and discussion of a historical paradox (i.e., the residual waiting time tends to increase with an increasing elapsed time under long-term memory) are also provided, based on the theoretical analysis of the Bayesian law and the stretched exponential distribution.

Effect of Rheology on Afterslip and Viscoelastic Patterns Following the 2010 Mw 8.8 Maule, Chile, Earthquake

2020 ◽  
Author(s):  
Carlos Peña ◽  
Oliver Heidbach ◽  
Marcos Moreno ◽  
Jonathan Bedford ◽  
Moritz Ziegler ◽  
...  
Keyword(s):  
Shear Strength ◽  
Power Law ◽  
Upper Mantle ◽  
Dislocation Creep ◽  
Viscoelastic Relaxation ◽  
Aftershock Activity ◽  
Plate Interface ◽  
Crust And Upper Mantle ◽  
Continental Lower Crust ◽  
Seismic Moment Release

<p>After large earthquakes at subduction zones, the plate interface continues moving due to mostly frictional afterslip processes. Below depths of 60 km, little frictional afterslip is to be expected on the plate interface due to low shear strength, lack of apparent geodetic interseismic locking, and low seismic moment release from aftershocks. However, inversion models that consider an elastic crust above a mantle with viscoelastic rheology result in a significant portion of afterslip at depths > 60 km. In this study, we present a forward 3D geomechanical-numerical model with power-law rheology that simulates dislocation creep processes for the crust and upper mantle in combination with an afterslip inversion. The linear rheology case is also considered for comparison. We estimate the cumulative viscoelastic relaxation and the afterslip distribution for the first six years following the 2010 M<sub>w</sub> 8.8 Maule earthquake in Chile. The cumulative afterslip distribution is obtained from the inversion of the residual surface displacements between continuous GPS (cGPS) observations and predicted displacements from viscoelastic forward modelling. We investigate three simulations: two with the same dislocation creep parameters in the slab and upper mantle but different ones in the continental crust, and another with elastic properties in the crust and slab and a linear viscoelastic upper mantle. Our preferred simulation is the one with power-law rheology in the crust and upper mantle with a weak continental crust since the corresponding afterslip distribution shows the best overall fit to the cGPS displacements (cumulative and time series) as well as having a good correlation with aftershock activity. In this simulation, most of the viscoelastic relaxation occurs in the continental lower crust beneath the volcanic arc due to dislocation creep processes. The resulting afterslip pattern from the inversion is reduced at depths > 60 km, which correlates well with the spatial distribution of cumulative seismic moment release from aftershocks. We conclude that by allowing for non-linear stress relaxation in the continental lower crust due to dislocation creep processes, the resulting afterslip distribution is in better agreement with the physical constraints from the shear strength of the plate interface at depth, the predicted locking degree, and the aftershock activity.</p>

Comprehensive Modeling of the Viscoelastic Relaxation Behavior of Polypropylene Tension Free Urinary Incontinence Tapes

2011 ◽  
Vol 3 (3) ◽  
pp. 183-187
Author(s):  
Dionysios E. Mouzakis ◽  
Stefanos P. Zaoutsos ◽  
Nikolaos Bouropoulos ◽  
Constantine Bouropoulos ◽  
Nikolaos Ferakis ◽  
...  
Keyword(s):  
Urinary Incontinence ◽  
Relaxation Behavior ◽  
Viscoelastic Relaxation ◽  
Tension Free ◽  
Comprehensive Modeling
Sign in / Sign up

Export Citation Format

Share Document