Slow Deformation Research Articles

Study on creep mechanism of coral sand based on particle breakage evolution law

The time-dependent deformation property of backfill coral sand is of great important to the long-term stability of engineer facilities bulit on reefs and reclaimed land. In order to investigate the long-term deformation behavior, one-dimensional compression creep tests under different constant stresses were carried out for coral sand taken from a reef in the South China Sea by WG type high-pressure consolidation instrument. The test results show that under the action of constant stress, coral sand has a strong deformation timeliness and shows remarkable nonlinear attenuation creep characteristics. The creep of coral sand has obvious stages and has gone through three stages of instantaneous deformation, accelerated deformation and slow deformation phase tending to stability. The relationship of strain-time can be fitted with power function in mathematic. The particle breakage state of any single particle size group of coral sand after creep can be well described by using the two-parameter Weibull distribution function, Weibull parameters a and b have a good exponential relationship with stress, and have a negative linear relation with quantitative index Br of particle breakage, and have a negatively correlated with final total strain. Under the action of low stress level, the main cause of creep deformation is the movement and recombination of particles. At low stress level, the movement and recombination of particles are the main reason of creep deformation, while at high stress level, the slippage and filling pores of broken coral sand particles are the main reason of creep deformation.

Algorithms for calculation damage processes

The paper reviews the existing approaches to calculating the destruction of solids. The main attention is paid to algorithms using a unified approach to the calculation of deformation both for nondestructive and for the destroyed states of the material. The thermodynamic derivation of constitutive relations for solids with elastic, viscous and plastic properties accounting possible destruction is presented. Explicit and implicit non-matrix algorithms for calculating the evolution of deformation and fracture development are presented. Implicit schemes are implemented using iterations of the conjugate gradient method, with the calculation of each iteration exactly coinciding with the calculation of the time step for two-layer explicit schemes. Therefore the solution algorithms are very simple. The results of solving typical problems of destruction of solid deformable bodies for slow (quasistatic) and fast (dynamic) deformation processes are presented. Recommendations are given for modeling the processes of destruction and ensuring the reliability of numerical solutions.

Optimization of phase-resolved optical coherence elastography for highly-sensitive monitoring of slow-rate strains

A realization of real-time optical coherence elastography for mapping small-amplitude, slowly varying strains is discussed. The technique is based on the recently developed ‘vector’ method for estimating interframe phase-variation gradients by considering complex-valued signals in optical coherence tomography (OCT) as vectors in the complex plane. This method is very tolerant to various measurement noises and allows for mapping both fairly fast and large, as well as rather small and slow-rate strains. Evaluation of strains slowly varying on intervals of ~tens of minutes is important for the emerging techniques of laser-assisted modification of collagenous tissues (e.g. for estimating post-reshaping stability of laser-modeled cartilaginous implants) or for studying slow deformations of osmotic origin in biological tissues. Optimization of the interframe interval for improving signal-to-noise ratio (SNR) in OCE-mapping of slowly-varying strains is discussed and experimentally demonstrated. The ultimate stability of strain estimation with the designed OCT setup is experimentally estimated using stable phantoms. Examples of the spatially resolved maps of slowly-varying strains are presented.

Measurement of the three-dimensional surface deformation of the Jiaju landslide using a surface-parallel flow model

ABSTRACTSAR Interferometry (InSAR) is a powerful technique for mapping land surface deformation, but single one-dimensional (1D) InSAR line-of-sight (LOS) measurement limits its application in three-dimensional (3D) displacement retrieval. Traditional methods were developed for measuring large-scale deformation. In this paper, to retrieve the slow 3D deformation process in the Jiaju landslide, a surface-parallel flow model is applied, according to the existing geological data gained from this landslide. Nine ENVISAT ASAR images and 19 ALOS PALSAR images were collected to reconstruct the 3D deformation field. An iterative method for correcting the characteristic value (IMCCV) with maximum likelihood estimation (M-estimation) adaptively generates an accurate stochastic model. The 3D deformation measurements show that the northern part of the Jiaju landslide clearly had horizontal deformation with the largest deformation velocity exceeding 15 cm year−1, while the southern part was relatively stable. Similarly, large vertical deformation appeared in the northern part (−2 cm year−1) and little deformation occurred in the southern part (−0.5 cm year−1). Compared with GPS measurements, the standard deviation is 1.4 cm year−1 and 0.7 cm year−1 in horizontal and vertical directions, respectively. Therefore, the Jiaju landslide exhibited movements in the horizontal direction accompanied by slight settlement in the vertical direction.

From gradual spreading to catastrophic collapse – Reconstruction of the 1888 Ritter Island volcanic sector collapse from high-resolution 3D seismic data

Volcanic island flank collapses have the potential to trigger devastating tsunamis threatening coastal communities and infrastructure. The 1888 sector collapse of Ritter Island, Papua New Guinea (in the following called Ritter) is the most voluminous volcanic island flank collapse in historic times. The associated tsunami had run-up heights of more than 20 m on the neighboring islands and reached settlements 600 km away from its source. This event provides an opportunity to advance our understanding of volcanic landslide-tsunami hazards. Here, we present a detailed reconstruction of the 1888 Ritter sector collapse based on high-resolution 2D and 3D seismic and bathymetric data covering the failed volcanic edifice and the associated mass-movement deposits. The 3D seismic data reveal that the catastrophic collapse of Ritter occurred in two phases: (1) Ritter was first affected by deep-seated, gradual spreading over a long time period, which is manifest in pronounced compressional deformation within the volcanic edifice and the adjacent seafloor sediments. A scoria cone at the foot of Ritter acted as a buttress, influencing the displacement and deformation of the western flank of the volcano and causing shearing within the volcanic edifice. (2) During the final, catastrophic phase of the collapse, about 2.4 km3 of Ritter disintegrated almost entirely and traveled as a highly energetic mass flow, which incised the underlying sediment. The irregular topography west of Ritter is a product of both compressional deformation and erosion. A crater-like depression underlying the recent volcanic cone and eyewitness accounts suggest that an explosion may have accompanied the catastrophic collapse. Our findings demonstrate that volcanic sector collapses may transform from slow gravitational deformation to catastrophic collapse. Understanding the processes involved in such a transformation is crucial for assessing the hazard potential of other volcanoes with slowly deforming flanks such as Mt. Etna or Kilauea.

Microstructure Formation of Low-Carbon Ferritic Stainless Steel during High Temperature Plastic Deformation

In this paper, the effects of the deformation temperature, the deformation reduction and the deformation rate on the microstructural formation, ferritic and martensitic phase transformation, stress–strain behaviors and micro-hardness in low-carbon ferritic stainless steel were investigated. The increase in deformation temperature promotes the formation of the fine equiaxed dynamic strain-induced transformation ferrite and suppresses the martensitic transformation. The higher deformation temperature results in a lower starting temperature for martensitic transformation. The increase in deformation can effectively promote the transformation of DSIT ferrite, and decrease the martensitic transformation rate, which is caused by the work hardening effect on the metastable austenite. The increase in the deformation rate leads to an increase in the ferrite fraction, because a high density of dislocation remains that can provide sufficient nucleation sites for ferrite transformation. The slow deformation rate results in dynamic recovery according to the stress–strain curve.

Evidence of Instability in Previously-Mapped Landslides as Measured Using GPS, Optical, and SAR Data between 2007 and 2017: A Case Study in the Portuguese Bend Landslide Complex, California

Velocity dictates the destructive potential of a landslide. A combination of synthetic aperture radar (SAR), optical, and GPS data were used to maximize spatial and temporal coverage to monitor continuously-moving portions of the Portuguese Bend landslide complex on the Palos Verdes Peninsula in Southern California. Forty SAR images from the COSMO-SkyMed satellite, acquired between 19 July 2012 and 27 September 2014, were processed using Persistent Scatterer Interferometry (PSI). Eight optical images from the WorldView-2 satellite, acquired between 20 February 2011 and 16 February 2016, were processed using the Co-registration of Optically Sensed Images and Correlation (COSI-Corr) technique. Displacement measurements were taken at GPS monuments between September 2007 and May 2017. Incremental and average deformations across the landslide complex were measured using all three techniques. Velocity measured within the landslide complex ranges from slow (> 1.6 m/year) to extremely slow (< 16 mm/year). COSI-Corr and GPS provide detailed coverage of m/year-scale deformation while PSI can measure extremely slow deformation rates (mm/year-scale), which COSI-Corr and GPS cannot do reliably. This case study demonstrates the applicability of SAR, optical, and GPS data synthesis as a complimentary approach to repeat field monitoring and mapping to changes in landslide activity through time.

Shear-induced martensitic transformations in crystalline polyethylene: Direct molecular-dynamics simulations

For the first time, we carry out molecular dynamics (MD) simulation of shear-induced martensitic phase transitions between the orthorhombic and non-orthorhombic (triclinic and monoclinic) phases of crystalline polyethylene (PE) in the framework of a realistic all atom model of the polymer. We show that the variation of the shear rate allows observing on a nano-sample both a strongly nonequilibrium phase transition occurring by random nucleation and irregular growth of a new phase ('civilian' way, for rapid deformations) and the coherent, or 'military', kinetics (generally considered as usual for martensitic transformations). We induce transitions from the orthorhombic to the triclinic phase according to two transformation modes observed in experiment on PE single crystals. Rapid deformation favors the transition directly to the triclinic phase, slow deformation - first to the intermediate monoclinic, and only then - to the triclinic phase. The second way corresponds to the experiment on extended chain PE. We explain this result and analyze the competition between different transformation and plastic deformation modes. Rotations of PE chains around their axes necessary for the transition between the orthorhombic and non-orthorhombic phases are executed by short twist defects diffusing along the chains. The transition between the monoclinic and triclinic phases occurs through half-chain-period translations of the chains along their axes, mostly collectively, as crystallographic slips.

Soil creep in a mesotidal salt marsh channel bank: Fast, seasonal, and water table mediated

Muddy banks of marsh channels experience soil creep – a viscous-like slow deformation resulting in a net downslope transport. Here we present the first field evidence of soil creep in a mesotidal salt marsh using both pole displacement and high precision measurements of soil deformation taken with a vibrating-wire extensometer over two years. Soil extended 2–4 mm/m/year in the high marsh platform and 20–40 mm/m/year in the low marsh bank. This was equivalent to a soil diffusivity of about 0.2 m2/year, which is much higher than the diffusivity on hillslopes and also matches the high value predicted by long-term marsh evolution models. High precision (±0.03 mm) soil deformation measurements shed light on the dynamics of the creep process. First, the low bank compressed and extended by ~5 mm/m every tidal cycle, suggesting that the diurnal changes in water level play a role in the bank movements. Second, net soil extension took place mostly during fall. Net soil extension preceded the period of ice formation, suggesting that freezing and ice rafting are not a leading cause of soil creep. Net soil extension was likely triggered by an increase in water table during fall, which decreased the effective stress and thus destabilized the bank. This high water table was caused by a combination of an abiotic factor – the increase in atmospheric precipitation – and a biotic factor – the decrease in evapotranspiration triggered by vegetation senescence. This study confirms that creep is a significant process in marsh morphodynamics and that vegetation can reduce mass wasting in marsh channels.

Testing Fault Models in Intraplate Settings: A Potential for Challenging the Seismic Hazard Assessment Inputs and Hypothesis?

Active faults in intraplate settings, exhibiting slow deformation, rarely expose clear morphotectonic expressions. In many cases, their characterization relies only on rare neotectonic slip rates, often integrated over the Holocene, Quaternary or Plio-Quaternary. In addition, the strain accumulated along these tectonic structures and therefore their locking depth and associated slip deficit usually remains out of reach of geodetic measurements. Finally, the micro-seismicity located in the vicinity of most of these structures usually fails in delineating clear active fault segments geometry. The seismogenic potential therefore remains tainted with large uncertainties. It is one of the main reasons why very little attention has been paid to testing how French seismicity compares to the predictions of tectonic models. In this work, focused on South-Eastern France, we confront the potentially active faults database of the French metropolitan territory with a recently published catalog of historical and instrumental seismicity. Seismicity rates are corrected for completeness biases and are then compared to the predictions of several endmember tectonic models. The rates of earthquakes predicted by the tectonic models appear six to eighteen times higher than the historical and instrumental observations. Such a difference could be explained by an overestimation of the seismogenic potential of the faults or by different average seismicity rates at historical and longer-term timescales. This variation, if genuine, could be implied by spatiotemporally clustered seismicity due to tectonic or non-tectonic modulations suggesting non-poissonian behavior of the largest earthquakes.

Electro-osmotic oscillatory flow of viscoelastic fluids in a microchannel

This work presents an analytical solution for electro-osmotic flow (EOF) in small amplitude oscillatory shear (SAOS) as a measuring tool suitable to characterize the linear viscoelastic properties of non-Newtonian fluids in microchannel flow. The flow in the straight microchannel is driven by applying oscillating sinusoidal electric potentials. Fourier series are used to derive an expression for the velocity field, under an externally imposed generic potential field aimed at the practical application of SAOS in characterizing the rheological properties of viscoelastic fluids. This extensive investigation covers a wide range of parameters and considers the multi-mode upper-convected Maxwell (UCM) model, which represents the rheology of viscoelastic fluids in the limit of small and slow deformations. Particular focus is given to two cases of practical interest: equal wall zeta potentials at both channel walls and negligible zeta potential at one of the walls. The results show that in flows with thin electric double layers (EDL), Reynolds numbers below 0.001, and Deborah numbers below 100, corresponding to a viscoelastic Mach number of 0.32, the velocity field outside the EDLs is linear and has a large enough amplitude of oscillation, which may allow the quantification of the storage and loss moduli in the linear regime. This technique requires the use of significantly smaller sample sizes than the traditional SAOS in a rotational rheometer.

Scaled Energy Estimation for Shallow Slow Earthquakes

AbstractDeep and shallow slow earthquakes occur at the edge of the seismogenic zone in the Nankai subduction zone. Deep slow earthquakes occur under high‐temperature and high‐pressure conditions, whereas shallow slow earthquakes occur at lower temperatures and pressures. Although these two types of slow earthquake show qualitatively similar behaviors, such as slow deformation and depleted high‐frequency seismic signals, their similarities have not yet been evaluated in quantitative ways. In this work, we analyze shallow tectonic tremors accompanied by very low frequency earthquakes off Kii Peninsula, Japan. We estimate the seismic energy of the shallow tectonic tremors by correcting for the site amplifications of ocean bottom seismic stations and seismic attenuation in the shallow accretionary prism. The estimated seismic energy rates of these tectonic tremors are compared with seismic moment rates of accompanying very low frequency earthquakes, revealing that the scaled energy of shallow slow earthquakes is roughly constant, ~10−9 to 10−8, which is 0 to 1 order of magnitude larger than the typical scaled energy of deep slow earthquakes.

APT: An Instrument for Monitoring Seafloor Acceleration, Pressure, and Temperature with Large Dynamic Range and Bandwidth

Research Article| January 15, 2019 APT: An Instrument for Monitoring Seafloor Acceleration, Pressure, and Temperature with Large Dynamic Range and Bandwidth Earl E. Davis; Earl E. Davis aPacific Geoscience Centre, Geological Survey of Canada, P.O. Box 6000, Sidney, British Columbia, Canada V8L 4B2, earl.davis@canada.ca Search for other works by this author on: GSW Google Scholar Martin Heesemann; Martin Heesemann bOcean Networks Canada, University of Victoria, 2474 Arbutus Road, Victoria, British Columbia, Canada V8N 1V9 Search for other works by this author on: GSW Google Scholar Joseph J. Farrugia; Joseph J. Farrugia bOcean Networks Canada, University of Victoria, 2474 Arbutus Road, Victoria, British Columbia, Canada V8N 1V9 Search for other works by this author on: GSW Google Scholar Greg Johnson; Greg Johnson cRBR Ltd., 95 Hines Road, Ottawa, Ontario, Canada 2K 2M5 Search for other works by this author on: GSW Google Scholar Jerome Paros Jerome Paros dParoscientific, Inc. and Quartz Seismic Sensors, Inc., 4500 148th Avenue NE, Redmond, Washington 98052 Search for other works by this author on: GSW Google Scholar Author and Article Information Earl E. Davis aPacific Geoscience Centre, Geological Survey of Canada, P.O. Box 6000, Sidney, British Columbia, Canada V8L 4B2, earl.davis@canada.ca Martin Heesemann bOcean Networks Canada, University of Victoria, 2474 Arbutus Road, Victoria, British Columbia, Canada V8N 1V9 Joseph J. Farrugia bOcean Networks Canada, University of Victoria, 2474 Arbutus Road, Victoria, British Columbia, Canada V8N 1V9 Greg Johnson cRBR Ltd., 95 Hines Road, Ottawa, Ontario, Canada 2K 2M5 Jerome Paros dParoscientific, Inc. and Quartz Seismic Sensors, Inc., 4500 148th Avenue NE, Redmond, Washington 98052 Publisher: Seismological Society of America First Online: 15 Jan 2019 Online Issn: 1943-3573 Print Issn: 0037-1106 © Seismological Society of America Bulletin of the Seismological Society of America (2019) 109 (1): 448–462. https://doi.org/10.1785/0120180132 Article history First Online: 15 Jan 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Earl E. Davis, Martin Heesemann, Joseph J. Farrugia, Greg Johnson, Jerome Paros; APT: An Instrument for Monitoring Seafloor Acceleration, Pressure, and Temperature with Large Dynamic Range and Bandwidth. Bulletin of the Seismological Society of America 2019;; 109 (1): 448–462. doi: https://doi.org/10.1785/0120180132 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract A simple tool has been developed to facilitate the study of interrelated geodetic, geodynamic, seismic, and oceanographic phenomena in marine settings. It incorporates quartz pressure and triaxial acceleration sensors and a low‐power, high‐precision frequency counter. The sensors are housed in a 6‐cm outside‐diameter, 1‐m‐long pressure case that is pushed vertically into the seabed with a submersible or remotely operated vehicle, with no profile remaining above the seafloor to cause current‐induced noise. The mass of the tool is designed to match that of the sediment it displaces to optimize coupling. Intrinsic measurement precision of the order of 10−8 of full scale (in this instance, a pressure range equivalent to 4000 m of water depth and an acceleration range of ±3g⁠) allows observations of pressure, acceleration, and tilt variations of 0.4 Pa, 0.6 μm s−2⁠, and 0.06 μrad⁠, respectively. Temperature variations measured near the top and at the bottom of the instrument are resolved to better than 0.1 mK. With the large dynamic ranges, high sensitivities and broad bandwidth (10‐Hz Nyquist to drift‐limited zero‐frequency DC), ground motion associated with microseisms, strong and weak seismic ground motion, tidal loading, and slow and rapid geodynamic deformation—all normally studied using disparate instruments—can be observed with this single tool. Examples of data are provided from four deployments with connections to the Ocean Networks Canada Northeast Pacific telemetred undersea networked experiment (NEPTUNE) observatory cable. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Моделирование временных эффектов необратимого деформирования на основе релаксационной модели пластичности

The analysis of plastic deformation of metals and polymethylmethacrylate under dynamic loading is carried out using a relaxation model of plastic deformation. The invariance of the parameters of the relaxation model of plasticity to the strain history allows us to obtain any set of deformation curves from a united viewpoint, both monotonic, with varying yield strength, and non-monotonic, with emerging and varying yield drop, as it is observed in experiments. The increase of the yield strength of high-strength 2.3Ni-1.3Cr steel together with the hardening effect both under high-rate and slow deformation is also modeled on the basis of the relaxation model. Using DP600 steel and nanocrystalline nickel as an example it is shown that the relaxation model of plasticity allows one to predict a smooth transition to the plastic deformation stage at slow quasi-static effects of ~ 10–3 s – 1, and also the appearance of a yield drop effect at strain rates of 500–6000 s –1. It is also shown that the developed approach allows one to simulate similar effects under high-rate deformation of polymethylmethacrylate. Thus, it was demonstrated using specific materials as an example that it is possible to effectively predict the deformation dependencies of the materials studied in a wide range of strain rates of 10-4-104 s-1 based on the parameters of the relaxation model of irreversible deformations.

Surface Deformation Monitoring in Coal Mine Area Based on PSI

It is difficult to get robust deformation results using conventional differential interferometric synthetic aperture radar (D-InSAR) method, due to the limitation of the phase measurement error, baseline error, and atmospheric delay in synthetic aperture radar (SAR) interferometry. Persistent scatterer interferometry (PSI) represents a powerful tool to measure mining subsidence, as it offers a synoptic view that can be repeated at different time intervals and at various scales. In many cases, PSI data are integrated with in situ monitoring instrumentation, since the joint use of satellite and ground-based data facilitates the geological interpretation of mining subsidence and allows a better understanding of mining subsidence geometry and kinematics. In this paper, PSI interferometry and conventional ground-based monitoring techniques have been used to characterize and to monitor Ge-Ting mining located in Shandong, China. The PSI technique used in this paper overcomes most of the limitations of conventional interferometric approaches by identifying, within the area of interest, a set of “radar benchmarks” (PS), where very precise displacement measurements can be carried out. More than 78000 PS were identified by processing SAR images acquired from 2004 to 2009 by the ENVISAT. The PSInSAR application at a sub-regional scale detected slow ground deformations ranging from 0 to −58 cm/year and resulting from various processes (swelling/shrinkage of clay soils and water pumping). The results reveal the evolution process of “bowl” in mining subsidence and are helpful to the early warning of the mine disaster.

Strong texture in nanograin bulk Nd–Fe–B magnetsviaslow plastic deformation at low temperatures

Nanograin magnets are potential candidates for ultrastrong magnets with high coercivity and high energy product. However, existing nanograin bulk magnets exhibit modest energy products because desired structures with nanoscale grain size and strong orientation (texture) are often difficult to obtain. This study describes a synchrony of the nanoscale grain size and strong texture in bulk Nd-Fe-B magnets by plastic deformation with slow strain rates at temperatures well below the melting point of the Nd-rich phase. High grain orientation (>90%) has been achieved for nanoscale grain sizes of 80-110 nm, giving the nanograin bulk magnets record high energy products (≥45 MGOe). Loosely-packed thick grain boundaries and creep-like stress-strain curves have been observed. Grain boundary mediated creep-like deformation is proposed as the mechanism for the high-degree nanoscale grain alignment under the deformation conditions without liquid phase. The effect of the strain rate on the texture and magnetic properties has been investigated systematically.

Mono-emulsion droplet stretching under direct current electric field.

We study the mechanism of stretching and breaking of a mono-emulsion droplet under a direct current electric field using theoretical and experimental approaches aided by numerical simulation. Axisymmetric straining flow driven by an electric field results in the equilibrium deformation of the droplet along the direction of the electric field if the electric capillary number Cae that is the ratio of electric stresses to capillary stresses, is less than a critical value (Cae)crit. At (Cae)crit, the droplet breaks either before showing the slow deformation stage or rapidly. Furthermore, we developed a theoretical model to understand the mechanism of the transition from equilibrium deformation to non-equilibrium breaking. The Cae that can induce Taylor's deformation D = (α - β)/(α + β) ≈ 0.295; where α and β are the lengths of semi-major and semi-minor axes of the droplet, corresponds to (Cae)crit. At this stage, the maximum flow velocity shifts to the outside of the droplet along the electric field direction and large electric stresses are mainly concentrated at the droplet's side apex causing daughter droplet ejection. Finally, we compare the values of (Cae)crit obtained from the theoretical model ((Cae)crit ≈ 0.25) for which the conductivity ratio (R) between the droplet and ambient liquid i.e., R ∼ O(10) with our experimental results ((Cae)crit ≈ 0.245) and realize that (Cae)crit decreases as R increases. We also observe that even though the viscosity ratio can alter the emulsion breakup modes, it has no effect on (Cae)crit for the onset of breaking.

Медленные деформационные волны как возможный предвестник сейсмической опасности

Медленные деформационные волны как возможный предвестник сейсмической опасности

Study of subsidence monitoring in Nanjing City with small-baseline InSAR approach

The surface subsidence in Nanjing has become increasingly apparent because of the influence of geological conditions and the rapid progress of urbanization. Here, the theory of synthetic aperture radar interferometry is analysed, and a method based on the short baseline subset (SBAS) technology is proposed. The method can overcome time and baseline decorrelation and other factors, and it can extract points with high coherence from interferograms have short spatio-temporal baselines when the atmospheric delay phase and the noise phase in the frequency domain are used to differentiate the corresponding characteristics. The slow deformation ratio of the monitoring area over long periods can also be calculated by this method. In this study, the 16 advanced land observing satellite (ALOS) data acquired from 2007 to 2011 in Nanjing are processed by the SBAS technology and compared with levelling result. This work emphasizes that the SBAS technology could derive the cumulative deformations of surfaces and deformation fields accurately.

Rapid deformation of IPMC under a high electrical pulse stimulus inspired by action potential

Slow deformation seriously restrains application development of IPMC actuator, especially for thick and ionic liquid-based IPMC. Inspired by the action potential of muscle cell, this letter proposes a concept of high electrical pulse stimulus to accelerate IPMC deformation. By analyzing the dynamic process of voltage drop at the electrode-polymer interface, high voltage pulse is proved theoretically to be safe for IPMC in a short time. After charging the electrical double layer at the interface, the voltage pulse should be reduced to a safe level before electrochemical reactions. In our experiments, applying various high voltage pulses to a thick IPMC, the deformation can be sped up a few hundred times at most without any electrolysis damage. The results strongly support the practicability of the impulsive driving method.