Electrical Resistance Tomography (ERT) is an advanced measurement technique owe to low cost, rapid response, no radiation, and non-intrusiveness, but there is a natural relation between internal ...electrical resistance (IER) distribution and external electrical resistance (EER) relative to a detected field. IER distribution can reconstruct the all the detected objects within the field while EER can greatly affect the measuring accuracy. So far, there is none effective method to compute the effect of EER. In this paper, a general method is proposed to analytically compute all measurements in the existence of EER. Inversely, according to the interrelation between IER and EER, IER can be solved based on all available measurements. To validate the proposed method, an important parameter of solid phase fraction based on IER was computed in dredging engineering. Results show that the new method can compute the value of solid phase fraction more accurate than the existing method, and thus can provide more accurate and practical measurements in the presence of EER.
Measuring transendothelial or transepithelial electrical resistance (TEER) is a widely used method to monitor cellular barrier tightness in organs-on-chips. Unfortunately, integrated electrodes close ...to the cellular barrier hamper visual inspection of the cells or require specialized cleanroom processes to fabricate see-through electrodes. Out-of-view electrodes inserted into the chip's outlets are influenced by the fluid-filled microchannels with relatively high resistance. In this case, small changes in temperature or medium composition strongly affect the apparent TEER. To solve this, we propose a simple and universally applicable method to directly determine the TEER in microfluidic organs-on-chips without the need for integrated electrodes close to the cellular barrier. Using four electrodes inserted into two channels – two on each side of the porous membrane – and six different measurement configurations we can directly derive the isolated TEER independent of channel properties. We show that this method removes large variation of non-biological origin in chips filled with culture medium. Furthermore, we demonstrate the use of our method by quantifying the TEER of a monolayer of human hCMEC/D3 cerebral endothelial cells, mimicking the blood-brain barrier inside our microfluidic organ-on-chip device. We found stable TEER values of 22 Ω cm2±1.3 Ω cm2 (average ± standard error of the mean of 4 chips), comparable to other TEER values reported for hCMEC/D3 cells in well-established Transwell systems. In conclusion, we demonstrate a simple and robust way to directly determine TEER that is applicable to any organ-on-chip device with two channels separated by a membrane. This enables stable and easily applicable TEER measurements without the need for specialized cleanroom processes and with visibility on the measured cell layer.
•Cell barriers are often quantified by transendothelial electrical resistance.•In organs-on-chips, fluid-filled microchannels are included in the measured path.•Non-biological changes in are often wrongly interpreted as changes in TEER.•We present a simple and universally applicable method to determine the TEER.•The applicability of this method was shown in a blood-brain barrier on chip.
Image reconstruction is a key problem for electrical resistance tomography (ERT). Because of the soft-field nature and the ill-posed problem in solving inverse problem, traditional image ...reconstruction methods cannot achieve high accuracy and the process is usually time consuming. Since deep learning is good at mapping complicated nonlinear function, a deep learning method based on convolutional neural network (CNN) is proposed for image reconstruction of ERT. To establish the database, 41122 samples were generated with numerical simulations. 10-fold cross validation was used to divide all samples into training set and validation set. The network structure was based on LeNet, and refined by applying dropout layer and moving average. After 346 training epochs, the image correlation coefficient (ICC) on validation set was 0.95. When white Gaussian noise with a signal-to-noise ratio of 30, 40, and 50 were added to validation set, the ICC was 0.79, 0.89, and 0.93, respectively, which proved the anti-noise capability of the network. The reconstruction results on samples which have more inclusions, different conductivity, and other shapes explained the network has good generalization ability. Furthermore, experimental data from a 16-electrode industrial ERT system was used to compare the accuracy of the proposed model with some typical reconstruction methods. Results show that the proposed CNN method has better reconstruction results than LBP, Tikhonov, and Landweber.
Oil-water two-phase flow is widely exists in the process of oil extraction and transportation. The measurement of water-to-liquid ratio (WLR) of oil-water two-phase flow is crucial for oilfield ...extraction, which not only helps to manage the oilfield production process, but also calculates the single-phase flow rate when the total flow rate is known. Electrical resistance tomography (ERT) is suitable for WLR measurements in today's fields at high water content, but requires calibration with measurements under full water conditions. Calibration values are often changed due to factors such as temperature and mineralization, and the originally obtained calibration values cannot be applied. In the past, manual recalibration was often required, but this recalibration process was cumbersome and costly. For this, a method based on impedance analysis is proposed to achieve the online calibration of ERT. First, the feature data for conductivity prediction is constructed by combining the measurement location information and frequency domain information of ERT; then, the conductivity prediction is achieved by using the modified residual network (ResNet)-18 deep neural network; finally, the mapping model from the conductivity value of water to the calibration value of ERT is constructed through approximately 30 h of experiments, which achieves the online calibration of ERT in the process of oil-water two-phase flow measurement. The proposed conductivity prediction model can reach the highest accuracy of 93.75% with no more than 5% relative error, and the accuracy of the mapping model from conductivity to ERT calibrated values is higher than 85% in all cases. Meanwhile, all errors are lower than 10%, proving the feasibility of the entire calibration process.
In horizontal well oil-water two-phase production profile logging, water holdup is one of the important parameters for inverse calculation of the flowrate of each phase. Among the flow pattern in ...shale oil wells, stratified flow and stratified flow with mixing at the interface play a dominant role. Stratified flow and stratified flow with mixing at the interface are classified mainly based on the quantity of bubbles in the oil-water two-phase interface. A water holdup calculation approach based on an array of electrical resistance probes is presented to distinguish between Stratified flow and stratified flow with mixing at the interface and to increase the accuracy of water holdup calculations. In addition to a flow loop simulation device as the main tool, a Single Arm Array Imager was used to simulate and measure the oil-water two-phase flow in horizontal wells under different conditions of well deviation (85°, 88° and 90°), flowrate and water cut. The oil-water phase interface mixing phenomena is shown to be more likely to occur at the well deviation of 85° and 88° based on the experimental data. The holdup imaging effect of the oil-water interface is improved by a probabilistic reconstruction approach using the measurement data from each resistive probe, and the average water holdup is computed. the absolute error between the average water holdup calculated herein and the experimental shut-in water holdup is less than 0.16. To sum up, a good effect was achieved in applying the above algorithm to oil-water two-phase horizontal well.
Calendering is an essential step to densify the porous structure of lithium-ion battery electrodes, enhancing the energy density and mechanical properties. This process involves mechanical ...interactions among particles and between particles and current collector. Microscopic damage from particle embedding into the current collector surface reduces the tensile strength, causing electrode fractures during calendering. This study investigated the evolution of electrode morphology, porosity, and specific surface area under incremental calendering. Additionally, the effects of active particle morphology and structural densification on electrode conductivity were analyzed. Microscale scratch and peel tests were conducted to determine the relationship between the line load and coating cohesion to analyzing current collector fracture behavior. The results show that an increased line load boosts coating cohesion but increases the susceptibility of the current collector to fracturing, ultimately reducing electrode fracture energy. This study elucidates the deformation and fracture mechanisms under the combined effects of coating densification and microscopic damage to the current collector during the calendering process, providing insights for optimizing process parameters and coordinated control.
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•The pore structure evolution of electrode during the calendering process has been defined.•The effect of the electrode structure on the electronic conductivity has been examined.•The fracture mechanism in the electrode calendering process has been detailed at a microscopic level.
An image reconstruction algorithm, which is developed for a 12-electrode capacitively coupled electrical resistance tomography (CCERT) system under 2-electrode excitation strategy, is proposed. Based ...on L-curve and Reginska's method, truncated singular value decomposition (TSVD) is used to reconstruct the initial image. The algebraic reconstruction technique (ART) algorithm is used to obtain the final reconstructed image. Image reconstruction experiments are conducted by a 12-electrode CCERT system. The proposed algorithm (TSVD + ART) is compared with conventional linear back projection (LBP), Tikhonov, Landweber, ART, simultaneous iterative reconstruction technique (SIRT), total variation (TV), conjugate gradient (CG), and TSVD to evaluate its image reconstruction performance. Image reconstruction results show the proposed algorithm (TSVD + ART) can effectively exploit the advantages of 2-electrode excitation strategy and hence realize higher quality image reconstruction. Under 2-electrode excitation strategy, the proposed algorithm has an obvious advantage over conventional image reconstruction algorithms. Under 1-electrode excitation strategy, the image reconstruction performance is comparable or slightly improved compared with that of conventional image reconstruction algorithms. Image reconstruction results also indicate the TSVD is effective to obtain the initial reconstructed image. The quality of the initial reconstructed image can be significantly improved compared with that of classic LBP, either under 2-electrode excitation strategy or 1-electrode excitation strategy.
Although progress with twisted graphene nano-devices is boosting the superconductivity that is the consequence of their Moiré flat electronic bands, the immense choice for future development is an ...obstacle for their optimisation. We report here that soft-chemistry deintercalation of KC8 breaks down graphite stacking generating a strong disorder that includes stacking twists and variable local doping. We obtain a bulk graphite whose individual crystallites have different stackings with arbitrary twists and doping, scanning in the same sample a huge number of stacking configurations. We perform magnetisation measurements on batches with different synthesis conditions. The disorder weakens the huge diamagnetism of graphite, revealing several phase transitions. A tiny “ferromagnetic-like” magnetisation appears with Curie temperatures T0∼ 450 K, that has to be subtracted from the measured magnetisation. Depending on sample synthesis, anomalies towards diamagnetic states appear at Tc∼ 110 K (3 samples), ∼ 240 K (4 samples), ∼ 320 K (2 samples). Electrical resistivity measurements yield anomalies for the Tc∼ 240 K transition, with one sample showing a 90% drop. We discuss the possibility that these (diamagnetic and resistive) anomalies could be due to superconductivity. As the amount of these phases is small by construction, fine-tuning of the process will be necessary to increase their fraction and select the desired phase.
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•Geopolymers have been synthesized using fly ashes from four different power plants.•Similar in chemical composition in fly ash doesn’t lead to similar strength.•Early age electric resistance of ...geopolymers is determined by the reaction rate.•Late age electric resistance of geopolymers is controlled by the chemical composition.
Geopolymer can be synthesized using industrial wastes such as fly ash, making it a promising material to replace Ordinary Portland Cement (OPC) as a green binder for concrete materials. One major barrier to prevent the wide application of geopolymer is that its properties heavily depend on the source materials. Aiming to evaluate the effect of fly ash on the properties of synthesized geopolymers, this study used four carefully selected fly ash to synthesize geopolymers. Comprehensive experimental programs have been carried out to characterize both the mechanical and electrical properties of these geopolymers. Mechanical testing shows that similar chemical composition in the source materials doesn’t guarantee similar compressive strengths of the produced geopolymers, and that high content of calcium doesn’t always lead to high compressive strength. Electrical characterization shows that both the magnitude of the electrical impedance and the electrical resistance of the geopolymers at early age measured at frequency of 10kHz increase with the curing time. It has also been found that at the early age, the electric resistance of the geopolymers is mainly determined by the reaction rate. At the late age, this electric resistance is mainly controlled by the chemical composition. Measurements over one year show that the bulk electric resistances or the diameters of the high frequency arcs of all geopolymers increase with age during the one-year testing period, suggesting that the geopolymerization is a very long process.
In this work, the electrical response of a multidirectional symmetric composite laminate with a delamination is studied analytically, numerically and experimentally.
An analytical model is initially ...developed to predict the electrical resistance of the composite laminate as a function of the delamination extent. The model was first validated against the results of a bulk of finite element analyses, considering different lay-ups and electrical resistivity. The model predictions were then compared to experimental data obtained through a dedicated experimental campaign performed on unidirectional and multidirectional Double Cantilever Beam (DCB) specimens. A satisfactory agreement was found in all the cases, thus supporting the accuracy of the analytical model.
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