Conductivity Probe Research Articles

Landslide‐dammed lake sediment volume calculation using waterborne ERT and SONAR profiling

AbstractLake sediment volume calculation is a challenging task, namely in cases when detailed drilling is complicated, expensive, or impossible, information on the pre‐sedimentation surface unavailable, and record of siltation rate non‐existent or too short. This study shows how waterborne, non‐invasive geophysical survey, such as electrical resistivity tomography (ERT) can be very effective in acquiring the missing data, namely when combined with sound navigation ranging (SONAR) water depth measurements and supported by information from auxiliary sources. However, ERT surveying in water environment requires specific approaches, as we illustrate on the case of the Mladotice lake study. The lake was created after a landslide in May 1872, and since its formation, the depth has gradually decreased due to sedimentation. We have reconstructed the original surface, calculated the sediment volume, and compiled information on sedimentation to estimate its remaining life span. To achieve this, we measured nine waterborne ERT profiles across the lake. To reach the necessary depth, all ERT profiles were extended on land and crossed the lake using custom‐built flotation pads. ERT profiling was combined with SONAR depth measurements, historical bathymetric surveys, borehole core analysis, sediment flux measurements, volumetric calculations, and water conductivity probing. The study has achieved three main results. First, practical applicability and advantages of stationary waterborne ERT profiling in combination with bathymetric sounding were demonstrated. Second, the original lake volume and accumulated sediment was calculated. We estimate that the volume of lake sediment is 187 000 m3, two‐thirds of the original lake volume (over 275 000 m3). Finally, based on three volumetric data sets from 1972, 2003, and 2017, and recent monitoring of the sediment inflow, we propose scenarios of lake filling and its future development. Most interestingly, the sedimentation rate has decreased significantly in the last 20 years, suggesting that the lake may survive much longer than hitherto expected. © 2020 John Wiley & Sons, Ltd.

Nano-Domains Produced through a Two-Step Poling Technique in Lithium Niobate on Insulators.

We proposed a two-step poling technique to fabricate nanoscale domains based on the anti-parallel polarization reversal effect in lithium niobate on insulator (LNOI). The anti-parallel polarization reversal is observed when lithium niobate thin film in LNOI is poled by applying a high voltage pulse through the conductive probe tip of atomic force microscope, which generates a donut-shaped domain structure with its domain polarization at the center being anti-parallel to the poling field. The donut-shaped domain is unstable and decays with a time scale of hours. With the two-step poling technique, the polarization of the donut-shaped domain can be reversed entirely, producing a stable dot domain with a size of tens of nanometers. Dot domains with diameter of the order of ∼30 nm were fabricated through the two-step poling technique. The results may be beneficial to domain-based applications such as ferroelectric domain memory.

Experimental dataset with high-speed visualization for vertical upward steam-water flow with transition from annulus to circular channel

A new database for steam-water flow is developed by the Multiphase Thermo-fluid Dynamics Laboratory (MTDL) at the University of Illinois at Urbana-Champaign. The experiment is carried out in a test section spanning the transition from an annulus to pipe, with one of the goals to study the effects of flow-geometry change on two-phase transport. Four-sensor conductivity probes are used to measure local two-phase parameters such as void fraction, interfacial area concentration, Sauter mean diameter, and gas velocity at 11 radial locations across the flow channel and five axial locations along the flow channel. The radial and axial profiles for selected conditions are presented and their features are discussed extensively. Parametric study is also carried out to understand the impact of flow parameters on steam-water flows under flashing condition. Besides, glass viewports are installed at three axial locations in the test section to observe the flow structure especially at the point of transition between the annulus and the pipe. The dataset, along with the high-speed videos, are valuable for the validation of the modeling and simulation of steam-water flows.

Theoretical study and experimental measurement of the gas liquid two-phase flow through a vertical Venturi meter

An accurate two-phase flow rate measurement is essential in many applications and industries such as; oil/gas, chemical, pipeline transportation and nuclear industry. This paper presents the findings obtained from two-phase flow rate measurements using Venturi meters coupled with conductance probe sensors. The measurement system and presented methodology can be used to directly and continuously measure the mass flow rate of gas-liquid flows without any need for using a separator. Most of the available data in literature on mass flow rate using Venturis in gas-liquid two phase flows are limited/valid to a certain flow regime. However, the experimental data presented in this paper covered a wide range of flows (i.e. bubbly, slug and churn flows). Three Venturis with different diameter ratios, β = 0.40, β = 0.55 and β = 0.75 have been employed using an air-water vertical test section. The effect of the Venturi’s geometry on the flow behaviour was also evaluated. The average void fraction and void fraction time series have been measured along the test section by nine different conductance probe sensors covering the convergent, throat and divergent sections. In addition, the two-phase pressure drop across the Venturi was measured. Moreover, a new correlation for the gas-liquid slip ratio was proposed in this paper, which is necessary for calculating the two-phase mass flow rate. The proposed slip ratio correlation showed more accuracy than the ones available in literature. It was found that the correlation proposed by Chisholm to predict the two-phase mass flow rate in Venturis with a diameter ratio, β = 0.55, shows the best accuracy among others such as; Murdock, Lin, James and Zhang correlations.

Method based on parallel‐wire conductivity probe for measuring water hold‐up in near‐horizontal oil–water two‐phase flow pipes

On the basis of a quick-closing valve technology, parallel-wire conductivity probes were designed to measure water hold-up of oil-water two-phase flow in near-horizontal pipe. First, the electric-field distribution characteristics of the parallel-wire conductivity probe and its response to the change of the water layer height were calculated by using finite-element method. Then, for the oil-water stratified distribution in the near-horizontal pipe with a 5° inclined angle, 20 mm inner diameter, and 1050 mm length, a measurement model for water hold-up was established. After that, a static experiment was carried out to investigate the accuracy of water-hold-up measurement. The results show that errors occur when the set water hold-up is with high values. The measurement errors were analysed based on curved oil-water interface predicted by Young-Laplace equation model, which are significantly related to the curvature of oil-water interface. It provides an effective experimental method for the measurement of water hold-up in a near-horizontal oil-water two-phase flow pipes. On the basis of this, the dynamic experiment of oil-water two-phase flow was carried out, and the slippage of oil-water two-phase flow was preliminarily revealed.

Experimental investigation of gas-liquid two-phase splitting in parallel pipelines with risers

To study two-phase flow splitting at a T-junction, Parallel vertical riser pipelines were set up in the laboratory. Each of these pipelines was completely symmetrical. The experiment was conducted with various combinations of gas velocity and liquid velocities. Accurate measurement of gas-liquid two-phase flow were performed to determine whether the two-phase flow was evenly distributed in the two riser pipelines. The conductance probe technique was used to measure the average liquid holdup in the cross section of the pipe. Three flow patterns in two risers were observed during the experiment: slug-slug (S-S), churn-churn (C-C), and churn-slug/churn (C-SC). Gas-liquid flow of S-S and C-SC is asymmetric, while that in C-C is symmetric. When the flow state in the two risers is S-S, the gas-liquid two-phase split could be uneven. When the gas and liquid velocities were sufficiently high for sustaining C-C, the gas and liquid were split evenly. The last state was the transition state between S-S and C-SC. A model based on pressure-minimization was established to predict two-phase flow splitting. The measured and predicted flow splits were observed to be in agreement.

High-speed digitization of the amplitude and frequency in open-loop sideband frequency-modulation Kelvin probe force microscopy

A more inclusive and detailed measurement of various physical interactions is enabled by the advance of high-speed data digitization. For surface potential characterization, this was demonstrated recently in terms of open-loop amplitude modulation Kelvin probe force microscopy (OL AM-KPFM). Its counterpart, namely open-loop frequency modulation Kelvin probe force microscopy (OL FM-KPFM), is examined here across different materials and under various bias voltages in the form of OL sideband FM-KPFM. In this implementation the changes in the amplitude and resonance frequency of the cantilever were continuously tracked as a conductive AFM probe was modulated by a 2 kHz AC bias voltage around the first eigenmode frequency of the cantilever. The contact potential difference (CPD) between the AFM probe and sample was determined from the time series analysis of the high-speed 4 MHz digitized amplitude and frequency signals of the OL sideband FM-KPFM mode. This interpretation is demonstrated to be superior to the analysis of the parabolic bias dependent response, which is more commonly used to extract the CPD in OL KPFM modes. The measured OL sideband FM-KPFM amplitude and frequency responses are directly related to the electrostatic force and force-gradient between the AFM probe and sample, respectively. As a result, clear distinction was observed for the determined CPD in each of these cases across materials of different surface potentials, with far superior spatial resolution when the force-gradient detection was used. In addition, the CPD values obtained from OL sideband FM-KPFM amplitude and frequency measurements perfectly matched those determined from their closed-loop AM-KPFM and FM-KPFM counterparts, respectively.

Observation of photovoltaic effect within locally doped silicon nanojunctions using conductive probe AFM

Abstract Localized p-doped nanojunctions (200–300 nm in diameter) were formed in n-type crystalline silicon substrates and were characterized using scanning electron microscopy (SEM) and conductive-probe atomic force microscopy (C-AFM). Localized doping was performed by diffusion through sub-micron sized holes in a silicon-oxide mask defined using self-organized polystyrene nanoparticles. After oxide removal, a significant brightness contrast in the SEM top and side view images strongly suggested the successful local doping of these areas. Furthermore, local current-voltage measurements performed by C-AFM revealed an open circuit voltage and a short-circuit current only in the areas defined as nanojunctions. This photovoltaic effect is driven by the laser used to control cantilever deflection in the AFM.

Electrochemical plasmonic optical fiber probe for real-time insight into coreactant electrochemiluminescence

Electrochemical surface plasmon resonance (ESPR) is a powerful technique for defining dynamic changes in chemical composition and morphology of functional interfaces by correlating spectral information with voltammetric characteristics of the electrode processes. However, conventional Kretschmann prism-based surface plasmon resonance (SPR) configurations require sophisticated apparatus and complex optics. Here, we present a versatile flow injection ESPR device that incorporates a plasmonic and conductive fiber optic probe, for which a gold nanohole array film is integrated onto the endface of a conventional optical fiber via template transfer. The coreactant-based Ru(bpy)32+ / tripropylamine (TPrA) electrochemiluminescence (ECL) system, was chosen to unravel electrochemically-induced real-time interfacial information, since such an approach is increasingly employed for clinical assay analysis and the associated ECL mechanism is an active area of investigation. The ESPR observations provide novel experimental evidence to support the proposition that the ECL reactions undergo an oxidative-reduction pathway. Moreover, the ESPR peak shift exhibits a broader linear detection range of TPrA concentration (0.02–20 mmol L−1, R2 = 0.996), compared to the ECL and SPR techniques (<10 mmol L−1). This study clearly demonstrates that the novel fiber optic ESPR device presents as a reliable and multimodal spectroelectrochemical platform to gain mechanistic insights into complicated chemical processes and provide sensing capabilities, while offering great simplicity, portability and miniaturization.

Optimization of gas parameters in a three-phase fluidized bed flotation column

The gas parameters, including gas holdup, bubble diameter and bubble specific surface area flux, of a three-phase fluidized bed flotation column (TFC) have been systematically studied. According to the characteristics of each stage of flotation the TFC is designed into three parts, the fluidized mineralization area, the buffer zone and the circulation section, and the solid particles are introduced into the fluidized mineralization area as regulatory factor. The gas holdup was calculated by measuring bed pressure drop, and the bubble diameter was measured by the conductivity probe method. Experimental parameters, including superficial gas velocity, superficial liquid velocity, solid particle type, frother concentration and initial static bed height, were studied. Experimental results show that the gas parameters can be optimized by changing experimental parameters. The models of gas parameters of the TFC have been derived. Experimental results have been compared with those in the relevant literature.

Four-sensor droplet capable conductivity probe for measurement of churn-turbulent to annular transition flow

In churn-turbulent to annular transition two-phase flow, both gas and liquid phase exist in the form of either continuous field (gas core/liquid film) or dispersed field (bubble/droplet). The complexity of the flow structure makes it very difficult to obtain experimental data in the churn-turbulent to annular transition flow. A novel four-sensor conductivity probe has been designed to measure interfacial structures at the churn-turbulent to annular flow regime transition. The new probe incorporates a sensor close to the detection point to serve as a common electrode for the other four sensors. Relatively large droplets can be identified and distinguished from the continuous liquid phase such as a liquid ligament or a film attached to the wall. To satisfy the higher requirements of the probe signal quality for the churn-turbulent and annular transition flow, the probe circuit has been optimized for a faster signal response and less interference. The new probe was tested in a 200 mm × 10 mm channel with an inlet superficial gas velocity up to 19.91 m/s. The measurement results are cross-checked by area-averaging the local superficial liquid and gas velocities and comparing with the measurements from a vortex flow meter and rotameter. The error is less than 10% for the superficial gas velocity and less than 20% for the superficial liquid velocity. The measured droplet size distribution is compared with a previous model, and good agreement is obtained. The effect of superficial gas velocity on droplet and ligament volume fraction as well as interfacial area concentration are investigated using the local measurement results of the three churn-turbulent to annular flow conditions.

Laser THz emission nanoscopy and THz nanoscopy

We present an experimental and theoretical comparison of two different scattering-type scanning near-field optical microscopy (s-SNOM) based techniques in the terahertz regime; nanoscale reflection-type terahertz time-domain spectroscopy (THz nanoscopy) and nanoscale laser terahertz emission microscopy, or laser terahertz emission nanoscopy (LTEN). We show that complementary information regarding a material's charge carriers can be gained from these techniques when employed back-to-back. For the specific case of THz nanoscopy and LTEN imaging performed on a lightly p-doped InAs sample, we were able to record waveforms with detector signal components demodulated up to the 6th and the 10th harmonic of the tip oscillation frequency, and measure a THz near-field confinement down to 11 nm. A computational approach for determining the spatial confinement of the enhanced electric field in the near-field region of the conductive probe is presented, which manifests an effective "tip sharpening" in the case of nanoscale LTEN due to the alternative geometry and optical nonlinearity of the THz generation mechanism. Finally, we demonstrate the utility of the finite dipole model (FDM) in predicting the broadband scattered THz electric field, and present the first use of this model for predicting a near-field response from LTEN.

Research on entrainment characteristics and Over-Reading model for gas-liquid flow in Venturi

The accurate measurement of gas-liquid flow is becoming increasingly significant in the oil and gas industry. Over-Reading (OR) model is the foundation for the gas-liquid flow measurement using Venturi. In this paper, a new OR model based on the form of Chisholm model for horizontal Venturi has been developed. The relationship between entrainment rate and OR in the throat of Venturi has been considered, which could be linked by the gas-liquid velocity slip. The liquid film thickness and entrainment rate in the throat of Venturi were measured by the conductance probes and cross-correlation method. The laboratory experiments of OR were conducted under the pressures of 0.2–1.4 MPa and at a wider range of Lockhart-Martinelli parameter (XLM:0–1.794). Without piecewise modeling, the relative errors of the new OR model are less than ±5% at the confidence level of 99.1%. The extension of the new OR model has been verified by the published data set of De Leeuw.

An affordable ammonia temperature-programmed desorption equipment and its calibration using the thermal decomposition of ammonium dihydrogen phosphate

A temperature-programmed desorption (TPD) equipment was built to follow ammonia release from solids; ammonia is detected following the ionic conductivity changes of saturated boric acid dissolution of with an ionic conductivity detector. The conductivity probe response is fast; it is insensitive to water, which is an advantage in the analysis of acid solids like zeolites and can be used with low heating rates or small samples. Ammonium dihydrogen phosphate (ADP) decomposition was used to calibrate the equipment and to check for its repeatability. In that process, it was found that the thermal decomposition of ADP was not well reported before. The decomposition of ADP follows a first-order kinetics and takes place in two steps; first, an ammonia molecule is released, and ammonia pyrophosphate is formed, then this decompounds to metaphosphoric acid and ammonia. Activation energies of 153 (4.6) kJ mol−1, and 69 (2.8) kJ mol−1, respectively, were calculated. NH3-TPD equipment requires a blank experiment due to the ability of the detector of sensing impurities in the carrier gas. Calibration of the technique gave a factor of conversion from conductivity to moles of ammonia of 347 (2.2) S m−1 mol−1 at 95.45% of confidence, a factor ten orders of magnitude higher than the limit of detection of the method calculated as 8.6 × 10-8 mole of ammonia. The limit of quantification was established as 2.9 × 10-7 mole of ammonia, a value quite low and useful when working with solid acids.

Autonomous Electrolyte Discovery for Batteries with Experimentally Informed Bayesian Optimization

An autonomous battery electrolyte experimental platform capable of mixing multi-component electrolyte systems and characterizing the transport and electrochemical properties in a high-throughput manner is disclosed. A Bayesian optimization software package found novel electrolyte compositions through optimization of the high-dimensional electrolyte design space over key design objectives like electrochemical stability and conductivity.Electrolyte optimization is difficult because 1) electrolyte evaluation is expensive and takes time, and 2) the space of possible electrolytes is expansive, formed by many possible choices for solvents (often in ternary blends), salts (often in binary mixtures), and trace additives. Bayesian optimization methods are well suited for the optimization of high-dimensional functions with costly evaluations, often producing an efficient design-of-experiments to converge on multi-objective optimal formulations in few experiments. To expedite the optimization over the expansive design space, theoretical predictions of electrolyte properties via the Advanced Electrolyte Model were utilized as “priors” in the statistical model.Implementation of the novel experimental platform was carried out by two novel test stands developed to automate the mixing and characterization of electrolytes: Otto (for aqueous systems) and Clio (for aprotic/organic systems). The test stands characterized the ionic conductivity and electrochemical stability of electrolyte systems, featuring a four-electrode conductivity probe, pH meter, and a flow-through three-electrode cell and potentiostat. Clio also integrated electrochemically active electrodes for optimization of electrolyte/electrode systems. The active electrode systems used were common functional ceramic metal oxides.A software orchestration and data layer linked the test-stands to human experimenters and machine-learning packages through a web-services architecture; all experiment data and meta-data is saved in a database. Additional out-of-the-loop characterization was conducted on cathodic systems to validate composition, structure, and oxidation state.The aqueous design space consisted of aqueous blends of lithium and sodium salts, including nitrates, sulfates, and other commonly-used battery salts. High-concentration aqueous electrolyte candidates were discovered by optimizing of electrochemical voltage stability and conductivity, including low-cost, high-performing alternatives to known but costly aqueous electrolytes (e.g. LiTFSI). Clio’s design space includes blends of both aprotic organic solvents and solutes in additional to various compositions of electrochemically active electrodes. The test-stands are demonstrated to be significantly faster than common human experimentation techniques, converging on novel, optimized electrolyte mixtures in mere hours or days of experimentation.

Distribution characteristics of falling film thickness around a horizontal corrugated tube

Falling-film evaporation has an essential method for desalination. The heat transfer tube is the core component of falling film evaporator. Liquid film thickness is one of the most important parameters for predicting heat and mass transfer coefficient of falling film evaporation. In this paper, a set of experimental apparatus for measuring the film thickness of a horizontal tube is set up. The experiments have been undertaken under different parameters, i.e. the tube diameter varying from 25 to 45 mm, the tube spacing ranging from 10 to 60 mm, the corrugated radius varying from 0.25 to 1 mm, and the film Reynolds number ranging from 150 to 1000. The liquid film falling around a horizontal tube is performed to explore the distribution characteristics of the film thickness. The liquid film thickness is measured by the conductance probe measurement method. The experimental results showed that the film thickness of the corrugated tube increases with the increasing of the film Reynolds number, which is the thinnest from 90° to 120°. It decreases as the tube spacing increases and increases with the tube diameter and corrugated radius. The liquid in the wave troughs can be replenished to the wave crests at any time because of the corrugated structure. The falling film thickness was thinner at the wave crests and thicker at the wave troughs. The phenomenon of dryout hardly appears in the falling film flow of the corrugated tube. Based on the experimental data, a new correlation has been given to predict the film thickness of the corrugated tube.

Liquid-phase turbulence measurements in air-water two-phase flows using particle image velocimetry

Liquid-phase turbulence plays a vital role in determining various gas-liquid two-phase flow parameters, such as void fraction distribution, bubble morphology, bubble-bubble interactions, and interfacial area concentration. In this study, a two-phase flow database including both the gas- and liquid-phases measurements was developed focusing on three bubbly flow conditions in an air-water two-phase flow loop with a vertical one-inch diameter circular pipe test section. A particle image velocimetry (PIV) system integrating an optical phase separation method, i.e., the planar laser-induced fluorescence (PLIF) technique using fluorescent particles and optical filtration, was applied to measure the liquid-phase turbulence information, including the time-averaged velocity, Reynolds stress, and turbulent kinetic energy for the liquid phase. The PIV measurements were taken at three ports along the test section at 14.5, 51.5, and 88.5 pipe inner diameters downstream of a bubble injector. In addition, a double-sensor conductivity probe was used to measure radial distributions of the local time-averaged void fraction and gas velocity. The measured liquid-phase turbulence was used to benchmark Sato's turbulence model considering the bubble-induced shear stress for the three tested bubbly flows. The benchmark results showed good agreement between the PIV measurements and model predictions. In the two bubbly flows tested that have low void fractions being less than 3%, the effect of the bubble-induced turbulence was found not significant. However, the bubble-induced shear stress becomes important with the increase of the void fraction.

An autonomous low-power instrument platform for monitoring water and solid discharges in mesoscale rivers

Abstract. We present the development of the River Platform for Monitoring Erosion (RIPLE) designed for monitoring at high temporal frequency (∼10 min) of water discharge, solid fluxes (bedload and suspended load) and properties of fine particles (settling velocity) in mesoscale rivers, i.e. which drain mesoscale catchments (≈10–103 km2). This platform responds to a request to continuously measure these variables in rivers using a single, centralized device, and to do this in the most direct way possible. The platform integrates the following instruments: (i) for water discharge, water level radar, and surface velocity radar, digital cameras and an echo sounder; (ii) for fine sediment load, turbidimeters and automatic samplers including the SCAF (a sediment settling velocity characterization device); (iii) for bedload, a hydrophone; and (iv) for water quality, a conductivity probe and water sampling. As far as water discharge monitoring is concerned, priority has been given to non-intrusive instruments to improve the robustness of the system. All the instruments are driven by a data logger (Campbell® CR6), which locally stores the data and then uploads them to a remote server every hour during the day using a 3G modem. SMS (Short Message Service) alerts can be sent depending on scheduled conditions (e.g. low battery voltage, water level threshold, all samples of the automatic sampler collected). The platform has been designed to be as autonomous as possible: it is powered by a battery that is supplied by a solar panel. Limiting the power consumption of the platform was one of the main technical challenges because of the quantity of instruments integrated. A simple 100 W solar panel is sufficient to power the entire platform, even during winter or low insulation conditions. A user-friendly interface has been developed, enabling to visualize the data collected by the platform from an internet connection. It is also possible to remotely configure the platform within this interface, e.g. to modify water sampling thresholds or alert thresholds. Finally, the platform is relatively easy to move from one site to another, because its installation requires little civil engineering. To date, RIPLE has been tested on two rivers of the Alps in France: the Romanche river in Bourg d'Oisans from September 2016 to July 2018 and the Galabre river in La Robine sur Galabre since October 2018, demonstrating the proper functioning of the platform.

Hydrodynamics and suspended particulate matter retention in macrotidal estuaries located in Amazonia-semiarid interface (Northeastern-Brazil)

The aim of the current study was to determine the nature of the seasonal variability of the Suspended Particulate Matter (SPM) fluxes from the drainage basin to the estuary in a macrotidal region (Northeastern Brazil), and the estuarine response to a seawater intrusion regarding sediment deposition, which will support the understanding of the global transport of materials at the continent-ocean interface. Thermohaline structure data was acquired using a Conductivity, Temperature, and Depth (CTD) probe with a sampling frequency of 4 Hz. Suspended particulate material was measured by gravimetric measurements applied to exact filtered volume samples. The outflows were measured through the use of an Acoustic Doppler Current Profiler (ADCP) with frequency of 1.5 MHz. The horizontal thermal and saline gradients varied from warmer and less saline waters (2014) to cooler and saline waters (2015). The gradient behavior when linked to volume transport and SPM flows, suggests a minimization of the fluvial flows in 2015, easing the advance of coastal water (CW) towards the inner estuary, leading to an inversion of the baroclinic pressure gradient. The bottom saline front, generated by the entrance of coastal water masses, caused an increase in SPM concentrations due to increased fluid density, resuspension of previously deposited sediment, and erosion of banks. High concentrations of SPM indicate higher volume transport suggesting a hydraulic barrier due to the change/inversion of the baroclinic pressure gradient, resulting in water and material retention. Material deposition was observed during neap tide, while during spring tide the material is resuspended, increasing the concentration, generating cycles of deposition and erosion during the neap-spring tides. The sediment in suspension that reach the estuary, even with low fluvial volume, stay in this environment forming new islands because of deposition. High deposition rates or sediment cycling, if generated by the hydraulic barrier, may indicate that the flows of SPM from the continental drainage to the estuary and adjacent continental shelf are interrupted and the residence time is increased.

Flexoelectric control of beams with atomic force microscope probe excitation

Based on the converse flexoelectric effect, flexoelectric actuator is designed and used to control the dynamic displacement of cantilever beams. First, shell-type stress expression based on double-curvature shell induced by the converse flexoelectric effect is developed, which can be simplified to a flexoelectric-laminated cantilever beam by applying two Lamé parameters and beam radius of curvature. Then, the flexoelectric actuator is designed with a conductive atomic force microscope probe and a flexoelectric layer. An inhomogeneous electric field is generated when the external voltage is applied on the atomic force microscope probe and the flexoelectric layer, which leads to stress in the longitudinal direction of beam and control moment. With the flexoelectric-induced bending moment, displacement induced by the external force and flexoelectric actuator is derived. The displacement is related to many parameters, such as actuation voltage, atomic force microscope probe radius and flexoelectric layer thickness. Cases are studied to optimize the control effect with different parameters. Results show that vibration control effect is enhanced with a higher actuation voltage and a smaller atomic force microscope probe radius for each mode. Besides, the thicker flexoelectric layer enhances the control effect with a larger bending moment arm for each mode. Dynamic vibration is controlled effectively by converse flexoelectric effect.