Capacitance Method Research Articles

Highly efficient capacitive removal of Cd2+ over MoS2-Carbon framework composite material in desulphurisation wastewater from coal-fired power plants

Cadmium (Cd2+) is the main toxic heavy metal in desulphurisation wastewater for coal-fired power plants. Here, a novel carbon skeleton/molybdenum disulphide composite material (MoS2/AC) with expanded layer spacing was synthetized in one step for Cd2+ removal through the capacitive deionization method. As the results showed, the Cd2+ removal capacity of the MoS2/AC cell was 22.15 mg g−1, and the concentration of Cd2+ in the simulated wastewater was effectively reduced from 10 ppm to <0.1 ppm. According to the characterisation, the layer spacing of MoS2 nanosheets in MoS2/AC increased by 58.06% compared with the original commercial MoS2, which could provide more active sites for Cd2+ adsorption. Moreover, the XPS results showed that electrosorption and complexation on the surface of MoS2/AC were the main routes for Cd2+ removal, especially the complexation between Cd2+ and metal-sulphur. In addition, the selective adsorption efficiency of MoS2/AC was more than 98% under the coexistence of other ions, such as Na+, Mg2+, and Ca2+. The regenerated MoS2/AC also had a high adsorption capacity for Cd2+ even after 5 cycles. The MoS2/AC material also exhibited excellent removal capability for heavy metal ions in the actual desulphurisation wastewater from coal-fired power plants (<1 ppb). The results indicated that MoS2/AC may be a prospective material for heavy metal ion removal from wastewater.

Continuous power production using flowable electrodes based on waste-heat assisted capacitive mixing

• A thermally assisted capacitive mixing system is proposed for harvesting low-grade heat. • The system can produce power continuously via adopting multiple electrode flow capacitors. • Various parameters are adjusted to optimize the performance of the system. • The thermal efficiency of the system is calculated based on the exergy analysis. • The temperature effect contributes to an increase in the power density of the system by a factor 1.5. The capacitive mixing method generates energy through spontaneous ionic mixing caused by the salinity gradient between sea and river waters. We introduce a continuous thermal regenerative system to combine an intermittent cycle with electrode flow capacitors using flowable slurries as electrodes to improve the efficiency of the existing capacitive mixing method by adding low-grade heat as another energy source. A continuous harvesting system was constructed to utilize the capacitive Donnan potential effect by switching the temperature and salt concentration with four separate reactors and two flow-electrode slurries. Experiments were conducted for continuous cycle operations by varying the active carbon and salt concentrations of the slurry as well as a single electrode flow capacitor test to evaluate the contributions of two different energy sources, i.e. , concentration and temperature differences. The continuous cycle operation was further optimized, resulting in a maximum power density of 3.84 mW/m 2 . Based on the exergy analysis, the theoretical thermal efficiency of the thermally–assisted continuous system was calculated at 10.8%. Waste-heat energy was successfully used for continuous power production using an electrode flow capacitor, and a continuous power generation cycle was implemented by combining the concentration and temperature differences without supplying external power.

Catalytic activity of nickel–copper powder alloys in the processes of electrochemical hydrogen evolution in alkaline solution and ethanol alkaline solution

Ni 93 Cu and Ni 82 Cu (at%) alloys were synthesized by the method of combined chemical reduction of Ni(II) and Cu(II) with hydrazine hydrate. These alloys consist of crystalline phases of nickel, solid solution of copper in nickel. Determination by the “capacitive method” of the electrochemically active surface area of working graphite electrodes with “catalytic inks” containing Ni 93 Cu and Ni8 2 Cu powders showed that it is 4 and 20 % larger than for nickel powder, respectively. It was found that powder alloys Ni 93 Cu and Ni 82 Cu are applicable as catalysts for the electrochemical process of hydrogen evolution in alkaline solutions and alkaline ethanol solution. It was determined that the catalytic activity of Ni82Cu powder alloy in the process of hydrogen evolution in the alkaline ethanol solution is higher than for nickel and Ni 93 Cu powders. The catalytic ability of the Ni 82 Cu powder alloy during cycling for 25 cycles practically does not change, in contrast to Ni and Ni 93 Cu.

Root electrical capacitance as an indicator of wheat growth and yield in a free-air carbon dioxide enrichment (FACE) experiment

Background and aimsThis study was the first to test the efficiency of monitoring root electrical capacitance (CR*) non-destructively in the field to evaluate crop development under different environmental conditions.MethodsA free-air CO2 enrichment (FACE) experiment was performed with two winter wheat cultivars, two levels (low and high) of nitrogen supply and two (ambient and elevated) of [CO2] in three replicate plots over two years. The validity of CR* as a proxy for root uptake activity was confirmed by tracking the ceptometer-based leaf area index (LAI).ResultsRepeated CR* measurements clearly demonstrated the seasonal dynamics in root development, with a peak at flowering, and the delayed growth in the second year caused by the unfavourable meteorological conditions. From the vegetative to flowering stages, CR* was strongly correlated with LAI (R2: 0.897–0.962). The positive effect of higher N supply and elevated [CO2] on crop growth was clearly indicated by the higher CR* values, associated with increased LAI, shoot dry mass (SDM) at flowering and grain yield (GY). The maximum CR* was closely related to GY (R2: 0.805 and 0.867) when the data were pooled across the N and CO2 treatments and the years. Unlike CR* and GY, SDM and LAI were significantly lower in the second year, presumably due to the enhanced root/shoot ratio induced by a severe spring drought.ConclusionsThe present results convincingly demonstrated the potential of the in situ root capacitance method to assess root responses dynamically, and to predict crop GY.

Development of time‐delay analysis method of inductance and capacitance for microfluidic circuit

AbstractIn this paper, we report the development of time‐delay analysis method of inductance and capacitance for microfluidic circuit. The sensor used in this method is composed of the sensing inductor (SI) and the sensing capacitor (SC) with a microfluidic circuit. This sensor measures inductance and capacitance in a time difference by delaying with microfluidic circuit. We confirmed that SI and SC have different responses to conductive and dielectric solution. This research is expected to be applied to the combined analysis of liquid samples.

Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device With Cylindrical Funnels

AbstractA convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier–stokes equation, energy equation, and turbulence equation is executed using ansysfluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in the number of funnels. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

Miniaturized pH‐Sensitive Field‐Effect Capacitors with Ultrathin Ta2O5 Films Prepared by Atomic Layer Deposition

Miniaturized electrolyte–insulator–semiconductor capacitors (EISCAPs) with ultrathin gate insulators have been studied in terms of their pH‐sensitive sensor characteristics: three different EISCAP systems consisting of Al–p‐Si–Ta2O5(5 nm), Al–p‐Si–Si3N4(1 or 2 nm)–Ta2O5 (5 nm), and Al–p‐Si–SiO2(3.6 nm)–Ta2O5(5 nm) layer structures are characterized in buffer solution with different pH values by means of capacitance–voltage and constant capacitance method. The SiO2 and Si3N4 gate insulators are deposited by rapid thermal oxidation and rapid thermal nitridation, respectively, whereas the Ta2O5 film is prepared by atomic layer deposition. All EISCAP systems have a clear pH response, favoring the stacked gate insulators SiO2–Ta2O5 when considering the overall sensor characteristics, while the Si3N4(1 nm)–Ta2O5 stack delivers the largest accumulation capacitance (due to the lower equivalent oxide thickness) and a higher steepness in the slope of the capacitance–voltage curve among the studied stacked gate insulator systems.

Development of Time-Delay Analysis Method of Inductance and Capacitance for Microfluidic Circuit

In this paper, we report the development of time-delay analysis method of inductance and capacitance for microfluidic circuit. The sensor used in this method is composed of the sensing inductor (SI) and the sensing capacitor (SC) with a microfluidic circuit. This sensor measures inductance and capacitance in a time difference by delaying with microfluidic circuit. We confirmed that SI and SC have different responses to conductive and dielectric solution. This research is expected to be applied to the combined analysis of liquid samples.

The LiNiO2 Cathode Active Material: A Comprehensive Study of Calcination Conditions and their Correlation with Physicochemical Properties Part II. Morphology

A better understanding of the cathode active material (CAM) plays a crucial role in the improvement of lithium-ion batteries. We have previously reported the structural properties of the model cathode material LiNiO2 (LNO) in dependence of its calcination conditions and found that the deviation from the ideal stoichiometry in LiNiO2 (Ni excess) shows no correlation to the 1st cycle capacity loss. Rather, the morphology of LNO appears to be decisive. As CAM secondary agglomerates fracture during battery operation, the surface area in contact with the electrolyte changes during cycle life. Thus, particle morphology and especially the primary particle size become critical and are analyzed in detail in this report for LNO, using an automated SEM image segmentation method. It is shown that the accessible surface area of the pristine CAM powder measured by physisorption is close to the secondary particle geometric surface area. The interface area between CAM and electrolyte is measured by an in situ capacitance method and approaches a value proportional to the estimated primary particle surface area determined by SEM image analysis after just a few cycles. This interface area is identified to be the governing factor determining the 1st cycle capacity loss and long-term cycling behavior.

Wireless Power Transfer and Management for Medical Applications: Wireless power

Wireless power transfer (WPT) plays an important role in medical devices that require contactless energy transfer for either direct powering or recharging their small batteries. Miniaturizing medical devices and improving their WPT link robustness against different variations (e.g., distance, alignment, and load changes) also demands an efficient and adaptive power-management IC (PMIC) to convert the incoming ac power carrier into one or multiple usable dc voltage supplies. This article summarizes the key techniques for WPT and PMIC design. It discusses different modalities for WPT, including inductive, ultrasonic, capacitive, and magnetoelectric (ME) methods, with a focus on their applicability in different types of medical devices with different dimensions, implantation depths, and power requirements. It is concluded that ultrasonic and ME modalities are suitable for WPT to deeply implanted small devices with low power consumption, while inductive and capacitive methods are more suitable for WPT to large implants with shorter depth and higher power consumption. This article also summarizes different PMIC techniques for inductive WPT, particularly conventional voltage mode and more recent current-mode (and reconfigurable) techniques, with an emphasis on their suitability for different input voltage and loading conditions.

Methodological aspects of studying the parameters of elastic waves and controlling the standard form of acoustic emission in the field

To measure the energy of the source of acoustic pulses in the absolute scale of units (J) from the registered pulses, an analysis of the energy balance &amp;quot;source of pulses&amp;quot; -- &amp;quot;transmitting medium&amp;quot; -- &amp;quot;receiver of pulses&amp;quot; was carried out using a spectral analysis device. Comparison of two independent methods for determining the energy of elastic interaction (capacitive method and photoelasticity method) gave a discrepancy between the results of less than 12%. The spectral composition of the interaction energy is determined. The results make it possible to determine both the parameters of the signal source and the structure of the transmitting average signal conversion. To measure stresses in an elastic wave, a piezoelectric receiver, in which a piezofilm served as a sensitive element. This receiver differs from receivers made on the basis of piezoceramic elements, has a significantly lower non-linearity of the amplitude-frequency characteristic, since it has only two natural frequencies. Keywords: photoelasticity, elastic wave velocity, rock mass, concrete, acoustic emission.

Analysis of Stretch-Dependent Capacitance and Its Effects on Energy Conversion of a Donut-Shaped Dielectric Elastomer Generator

Dielectric elastomer generator (DEG) comprises of soft and stretchable capacitive transducer. The DEG experiences a change in capacitance and provides a voltage gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G$ </tex-math></inline-formula> ) with an applied mechanical excitation. This article interprets DEG as a machine that involves a cyclic change of finite-state transducer capacitances to transmit or modify energy. In this study, a relative analysis of capacitances associated with the DEG transducer is introduced and analyzed to improve the DEG performance. This article focuses on defining a relationship between the material stretch ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda$ </tex-math></inline-formula> ) and finite-state capacitances associated with the DEG transducer. The estimation of stretch-imposed DEG capacitance under mechanical excitation is well investigated. Eventually, the analysis is experimentally validated with the developed mechanical prototype. For distinct transducer deformation, the associated capacitances are estimated with the capacitive extensometer method and the stretch ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda$ </tex-math></inline-formula> ) is calculated. Moreover, for effective energy conversion, the finite state capacitance variation is maintained large enough to provide a relatively high voltage gain. Experimental results show that for 70% increase in capacitance difference at the DEG makes the specific energy increase from 3.5 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11.5~\mu \text{J}$ </tex-math></inline-formula> /g. This study could lead the DEG as an alternative power source for low-power electronic gadgets.

Wideband Microwave Sensor for Downhole Water-Cut Monitoring

In the petroleum industry, downhole water-cut loggings are essential for reservoir management. Previously, most of them are based on permittivity measurements by low-frequency capacitance methods. However, they fail to work in aging oil fields with high water cuts and highly mineralized subterranean water. In this article, a nonresonant self-calibrated wideband microwave sensor is proposed to solve this problem. Taking advantage of the Cerenkov-like enhanced radiation of coaxial leaky-wave antennas, sufficient signals can be received even when the fluid under test (FUT) is highly conductive. An accurate wideband forward model has been established with no empirical or undetermined quantities. Complex permittivities and water fractions of the FUT can be retrieved without calibrations, making the sensor especially suitable for the downhole working conditions with unknown temperature drifts. NaCl solutions with different concentrations (0–130 g/L), oil–water emulsions with different water fractions (70%–100%), and ethanol–water solutions have been tested in the frequency band ranging from 1 to 8 GHz. Dielectric constants and conductivities of the NaCl solutions range from 40 to 80 and from 0 to 15 S/m, respectively, covering the main measurement ranges of high-water-cut monitoring.

Economic evaluation of fluoride removal by membrane capacitive deionization

Today, one of the most important issues of all is the supply of drinking and utility water, which is the most basic need for human beings, to be healthy and reliable, economical. Some substances in natural water sources pose a danger to living creatures when they exceed certain concentrations. Fluoride, which can be commonly found in water as a result of natural or industrial effects, poses various risks for the living not only in its deficiency, but also its excess. Therefore, the fluoride concentration should be under control. Membrane Capacitive Deionization Process is an effective method to remove ions from water. In this study, firstly, optimum conditions have been determined by working on the removal of fluoride from groundwater with MCDI which is prepared synthetically. Subsequently, the groundwater, which was obtained from Isparta province and containing 7.71 mg/L fluoride, was treated by the membrane capacitive deionization method at the optimum conditions determined by 99%. Groundwater fluoride concentration has been reduced below the drinking water fluoride limit. For this treatment, 0.06 kWh/m3 energy was expensed and this corresponds to an energy cost of $ 0.006/m3. These results are quite economical when compared to other groundwater fluoride removal methods.

Comparative dielectric study of bent-core liquid crystal doped 5CB

Bent-core liquid crystal (LC) is used to dope the (4-cyano-4′-pentylbiphenyl) liquid crystal (5CB). The polarizing microscopy results show that 5CB and LC exhibit Nematic (N) and Banana-Shaped (B1) mesophases, respectively. In this paper, we use dielectric spectroscopy to determine the dielectric properties of the 1% LC doped with 5CB liquid crystal. The dielectric parameters of these materials have been determined by different applied voltage. In this respect, dielectric properties of 5CB + 1% LC have been compared with 5CB. The dielectrical anisotropy of 5CB and 5CB + 1% LC liquid crystal composite changes from the positive dielectric anisotropy to negative with the frequency of the applied voltage. The critical frequency fc values of dielectrical anisotropy for 5CB and 5CB + 1% LC composite were found to be 688 and 534 kHz, respectively. The real (ε′) and imaginary components (ε′′) of dielectric constant have been calculated by capacitance method. It has been also determined that adding LC to 5CB decreases the voltage dependent dielectric strength and increases threshold voltages.

Optimization Technique for High-Gain CMOS Power Amplifier for 5G Applications

In this study, a differential power amplifier (PA) with a high gain of over 30 dB by configuring a three-stage common source unit amplifier was designed. To ensure the stability of the high-gain differential PA, the analysis to apply the capacitive neutralization method to the differential common source PA was conducted. From the analysis, the required neutralized capacitance was quantitatively calculated from the estimated parasitic components of a power cell used in the PA. To verify the feasibility of the proposed optimization technique, a Ka-band PA was designed with a 65 nm RFCMOS process. The measurement results showed a gain of 30.7 dB. The saturated output power was measured as 16.1 dBm, maximum power-added efficiency (PAE) was 29.7%, and P1dB was 13.1 dBm.

Experience in registration of evaporation of liquid drops on a substrate by the capacitive method

This paper presents the results of an experimental study of the dynamics of evaporation of nanofluid droplets based on distilled water with a mass concentration of SiO2 nanoparticles of 0.1%, 0.5%, and 7% lying on a metal surface. The drop height was changed over time using original equipment, which is based on an integrated approach to the combined use of capacitive and optical recording methods. The experimental results show that the change in the height of nanofluid droplets with concentrations of 0.1%, 0.5%, and 7% is linear over the main part of the evaporation time interval. A deviation from the linear law is observed at the final stage, at the time interval of complete evaporation. The time for complete evaporation of droplets of nanofluids with a concentration of 0.1% increases by 20%, for droplets with a concentration of 0.5%, it increased by 28% in comparison with the evaporation of droplets of the base liquid. The particle concentration of 7% does not lead to an increase in the evaporation time of droplets in comparison with the evaporation of low concentration droplets. Before the formation of a jelly-like residue of nanoparticles, the evaporation rate of droplets with a particle concentration of 7% is comparable to the evaporation rate of droplets with a concentration of 0.1%.

Charge-Based Capacitive Self-Sensing With Continuous State Observation for Resonant Electrostatic MEMS Mirrors

This contribution presents charge-based capacitive self-sensing with a continuous full state observer for a parametrically driven resonant electrostatic 1D MEMS mirror considering precise and seamless estimation. Based on current integrators, series capacitances or a capacitance network the direct charge self-sensing principles are investigated and compared considering leakage currents, precision and a minimum implementation effort. In comparison to the other charge sensing methods, the proposed methods directly measure the charge changes while the drive voltage is switched on. Since resonant MEMS mirrors are driven by a rectangular signal, the direct self-sensing implies a lack of data when the drive voltage is switched off. A nonlinear observer is also proposed to estimate the full mirror state continuously based on an identified MEMS mirror model. The capacitive charge self-sensing methods achieve overall a high sensing precision of less than 0.14 % RMSE and the observer estimation error of the full state is below 1 % peak-to-peak error regardless of the availability of the charge self-sensing measurements, demonstrates accurate continuous full state estimation. [2021-0130]

Comparative testing of two alternating current methods for determining wood moisture content in kiln conditions

Abstract Research into the possibility of applying the electric impedance spectrometry (EIS) method and the dielectric capacitance method (DECM) simultaneously above fibre saturation point (FSP) and in harsh kiln conditions has been relatively scarce. In the framework of this research, tests were carried out on the operational reliability of the measuring capacitor (MEC) prototype used for calibrating the DECM in the harsh internal climate (50°C and 98% RH) of the kiln. Condensation of water vapor on MEC plates, leakage of MEC insulators and the emergence of static electric charges on MEC plates were studied. Quantitative ranges were found for MEC performance-disrupting effects on the parasitic capacities induced by each effect. The DECM was found to be less reliable than the EIS method for application in harsh kiln conditions. Secondly, under the same test conditions and for the same wood species (birch), the possibilities of the DECM method and the EIS method were comparatively modeled with the predetermined Rozema quality criterion of ±1.75% MC for predicting the moisture content (MC) of birch wood above FSP. It was found that, under the same test conditions, the DECM method proved more accurate than the EIS method for predicting birch wood MC above FSP. Based on the tests, it was concluded that DECM can be used in practice by applying a non-destructive method to reliably determine the average moisture content of a wood batch immediately prior to commencing the wood-drying process.

A Novel Capacitive Method for Urodynamic Measurements That is Suitable for Home Use

Purpose: Urinary incontinence is highly prevalent in both women and men. Urodynamic testing is essential for diagnosis, but a gap exists in the usefulness of simple assessments that do not provide sufficient data, and devices that provide the necessary data, but are used primarily in clinics and clinical trials. This study considered the existing methods of urodynamics testing and developed a device that was both effective and suitable for home use.&#x0D; Methods: A review of existing urodynamic methods led to development of a capacitive device. We created a device with sensor electrodes placed on the outside of a specimen container. The functionality of the electrodes and performance of the novel capacitive device were compared with that of a gravimetric device (Dorado KT, Laborie Medical Technologies, Mississauga, ON, Canada) used at the University Clinical Center, Maribor.&#x0D; Results: Measurements of fluid volume (p = 0.936), maximum (p = 0.327), and mean (p = 0.136) flow observed with the two devices were not significantly different. Graphical analysis of collected volumes and flow variation over time show a high degree of overlap.&#x0D; Conclusion: Compared with previously developed urodynamics testing devices, the capacitance method and the performance of this device represent an advance. The precision of the measurements needs improvement and did not fully address the recommendations of the International Continence Society, but he use of additional sensor electrodes is expected to improve performance. Extending the functionality as a standalone capacitive device for home use and upgrading with wireless access by mobile systems would allow for additional benefits beyond current voiding diaries.