Part Of Capacitance Research Articles

Study of high-frequency impedance of zinc-rich coatings

In this paper, three types of impedance spectra were investigated, i.e., impedance spectra of two zinc powders (new and old) and five coatings (two different thicknesses of epoxy zinc-rich coatings (EZRCs), an ethyl silicate zinc-rich coating, an epoxy coating and an autodeposition coating) in 3.5 wt.% NaCl solution, dry film impedance spectra of two coatings (the thicker EZRC and autodeposition coating) and their impedance spectra in a 0.003 M LiCl–methanol solution. The results show that the resistive part of the high-frequency impedance of the ZRCs at the early stage of immersion is the contact resistance ( Rm) between the zinc powders, and the capacitive part is the parallel connection of the contact capacitance ( Cm) and the film capacitance ( Cc) of the binder. The coupling of the two capacitors results in a deviation of the measured Pm from the true Pm, where Pm is the Cm-dependent dispersion coefficient

Low-frequency capacitor with hopping electrical conductivity of the working substance (on the example of a-Si:H)

We propose a structural and electrical schemes of a capacitor based on a 3 μm thick a-Si:H (amorphous hydrogenated silicon) layer separated from the metal plates by 0.3 μm thick dielectric layers of SiO2 (silicon dioxide). We consider room temperatures (T ≈ 300 K) when in the absence of illumination for a-Si:H the hopping mechanism of electron migration via point defects of the structure prevails. For such a capacitor, the dependencies of the capacitance on the frequency of the measuring signal ω/2π in the range from 0.1 to 300 Hz are calculated for the a-Si:H layer with stationary hopping electrical conductivity σdc ≈ 1 ∙ 10−10 (Ohm ∙ cm)−1. It is assumed that there is no end-to-end electron transfer between the a-Si:H layer, dielectric layers and capacitor plates in the small-signal mode of capacitance measurement. It is shown that the real part of the capacitance of the capacitor decreases with increasing angular frequency ω, and the imaginary part is negative and depends non-monotonically on ω. The decrease in the real part of the device capacitance to the geometric capacitance of the series-connected oxide layers and the a-Si:H layer with increasing ω is due to a decrease in the electrical resistance of the capacitor. As a result, with increasing ω, the imaginary part of the capacitance is shunted by the hopping electrical conductivity of the capacitor. The phase shift for a sinusoidal electrical signal supplied to the capacitor is determined depending on the frequency ω/2π in the range of 0.1–300 Hz for the values of electrical conductivities of the hydrogenated amorphous silicon layer σdc ≈ 1 ∙ 10−11, 1 ∙ 10−10, and 1 ∙ 10−9 (Ohm ∙ cm)−1 at the temperature 300 K. With an increase in the electrical conductivity σdc of the a-Si:H layer, the minimum absolute value of the phase shift angle (≈65°) shifts to the high- frequency region (from 1 to 100 Hz). The proposed low-frequency capacitor can find application in electrical circuits for detecting low-frequency electrical signals for the purposes of biomedicine.

Surfactant assisted tuning of electrical conductivity, electromagnetic interference shielding effectiveness, wetting properties of poly(lactic acid)-expanded graphite-magnetite nanocube hybrid bio-nanocomposites

The study aimed at demonstrating polyvinylpyrrolidone (PVP) amount is critical for tuning electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of poly(lactic acid)-expanded graphite (ExGr)-magnetite (Fe3O4) nanocube hybrid nanocomposites. An optimum loading of PVP (1 wt.%) was found to disperse the nanofillers resulting in enhanced electrical conductivity and EMI SE in the X-band dominated by the absorption mechanism. The electrical conductivity enhancement in hybrid nanocomposites was not only attributed to the network formation between fillers but also to the thickness of the coated surfactant layer. The inter-junction capacitance and real part of relative permittivity of the hybrid nanocomposites were also enhanced at 1 wt.% PVP addition in comparison to 0 wt.% and 2 wt.% surfactant loading. The water contact angle was found to depend on the surface roughness of the film, which varied with both PVP and ExGr loadings. These PLA-based hybrid nanocomposites can be used as microwave-absorbing material.

An electrode-impedance-aware neurostimulator IC that achieves low-power consumption and fast charge balance

Implantable neural stimulation is becoming increasingly popular for treating neurologically impaired patients, restoring neural functions which would otherwise be lost due to diseases or injuries. The charge balance of the stimulus pulses is of paramount importance for the long-term safety of the electrode-tissue interface. This paper presents a novel neurostimulator integrated circuit in which two novel charge balancing schemes are proposed. One is based on acquiring the access resistance part (RS) of the inter-electrode impedance. Thanks to its adaptive anodic phase, the RS-based charge balance circuit does not require an additional discharge phase, achieving faster charge balance than most existing stimulator ICs. The other scheme is based on acquiring the double-layer capacitance part (CDL) of the inter-electrode impedance and the entire charge balancing process (inc. monitoring, computation and compensation) is performed in the analog domain. This is in sharp contrast to the existing electrode-impedance-aware charge balancing schemes which require ADCs and compute the net charge in the digital domain. Hence the new impedance-aware charge-balancing scheme is faster and more power friendly. The impedance-aware stimulator ASIC has been implemented using X-FAB’s 180-nm CMOS process. The post-layout simulation results suggest a good charge balance is achieved as the voltage deviation from the electrode offset voltage on the electrode after the charge compensation reduces to 2.64 mV and –1.39 mV under the RS-based and CDL-based charge balancing schemes, respectively. The additional power overhead due to the proposed CDL-based charge balancer circuit is 2.46 μW at a stimulation rate of 400 Hz.

Application of in-situ EIS to Galvanic Corrosion of Aluminum Alloy Coupled with High-Tensile Steel

Toward multi-materials for the weight reduction of automobile bodies, the light materials have been used in the automotive industry. However, it may pose serious issues for degradation due to the galvanic corrosion. In this study, an in-situ electrochemical impedance spectroscopy (in-situ EIS) 1-4 was applied to the evaluation of galvanic corrosion of aluminum alloy coupled with high-tensile steel. This method allows for the simultaneous measurement of impedance spectra of aluminum alloy and high-tensile steel.An electrochemical measurement was performed by a three-electrode system. The working electrode (WE) was an aluminum alloy plate, the counter electrode (CE) was a high-tensile steel plate. The reference electrode (RE) was a saturated KCl-Ag/AgCl (SSE), which was set near the WE and CE. To simulate the galvanic corrosion environment of automotive materials, the aluminum alloy plate and high-tensile steel plate are set face-to-face. The distance of both electrodes was about 100 μm. The 3D impedance measurement was carried out for 2 weeks. In this measurement, the potential difference between the WE and the CE was set to 0 V to simulate galvanic corrosion 5. The frequency range was 10 kHz to 0.1 Hz at 5 frequencies per decade and AC potential amplitude was 10 mV. The electrochemical cell was placed in the temperature and humidity chamber for the wet and dry cyclic corrosion test.The in-situ EIS was successfully carried out during the wet and dry cyclic corrosion test in the temperature and humidity chamber. The three-electrode system enables the simultaneous measurement of impedance of aluminum alloy plate - high-tensile steel plate (WE-CE), aluminum alloy plate (WE), and high-tensile steel (CE). In the wet condition, the capacitive loop and part of large loop in the high and low frequency ranges were observed in the instantaneous impedance of the aluminum alloy plate-high tensile strength plate (WE-CE) determined from 3D impedance 1-4 at arbitrary time. In this case, the instantaneous impedance of the aluminum alloy plate (WE) and high-tensile steel plate (CE) described the capacitive loop and part of large loop on the Nyquist diagram respectively. It was confirmed that the capacitive loop and part of large loop in the high and low frequency ranges observed in the instantaneous impedance of the aluminum alloy - high tensile strength (WE-CE) were related to the aluminum alloy plate (WE) and high tensile strength plate (CE), respectively. The galvanic corrosion behavior during the wet and dry cyclic corrosion test was investigated by evaluating the charge transfer resistance estimated from the instantaneous impedance of the aluminum alloy plate (WE) and high-tensile steel plate (CE) to discuss the time variation of the charge transfer resistance.

The Research on the Improvement of the Zero-Sequence Relay for the Low Resistance Grounded Power Grid

In the low resistance grounded power grid, when a high-impedance grounding fault occurs at a distribution line, the zero-sequence fault current is not big enough to make the zero-sequence over-current relays trip because of the setting limitations, and thus the earth fault would exist for a long time with no alarm signal. As a result, there would be a hidden danger that the grounding fault might cause further faults or cause harm to personal safety. To solve the problem, in the paper, the characteristics of zero-sequence components when the high-impedance grounding fault occurs are analyzed, and the practicability and the deficiency of the directional zero-sequence over-current relay are pointed out. Based on the analysis, an improved zero-sequence relay with the resistance-capacitance ratio restriction is raised. The resistance-capacitance ratio restriction condition is based on the different structures of the resistant part and the capacitive part of zero-sequence currents, and the faulted line can be identified with the resistance-capacitance ratio criterion. The resistance-capacitance ratio criterion is not influenced by the polarity of the voltage transformer (VT) and current transformer (TA) and can avoid the influence caused by the reversed polarity of the exclusive zero-sequence TA. With the improved zero-sequence over-current relay with the resistance-capacitance ratio restriction, the ability to identify high-impedance grounding faults can be improved, and the fault area can be isolated quickly, to guarantee the reliability and safety of the operation in power grids.

Studies on the nonlinear dielectric response in ferroelectric–dielectric composite system

The nonlinear dielectric response (NDR) of Bi3.25La0.75Ti3O12–Al2O3 systems has been studied. To reveal the effects of the dielectric layer (DL) systematically, a method based on the equivalent circuit analysis and parametric study is proposed. The consistency between the calculated results and the experimental results manifests the validity of the method. In addition to the Rayleigh coefficients varying monotonically with the capacitance of DL, it is revealed that the slope between the real and the imaginary parts of the complex capacitance under different ac voltages is related to the relative loss values of DL and the ferroelectric layer. The frequency dependence of the NDR parameters is also discussed. The method established in this work is useful for research on the devices based on the ferroelectric–dielectric system and the ultra-thin ferroelectric films.

Porous activated carbon and highly redox active transition metal sulfide by employing multi-synthesis approaches for battery-supercapacitor applications

Transition metal sulfide due to high theoretical capacity, large active sites, non-toxic and higher conductivity make them more favorable for energy storage applications. Therefore, we have synthesized Nickel sulfide by employing multiple approaches to study their electrochemical properties and utilized it for practical applications. Initially, the sample was confirmed by performing X-ray diffraction and scanning electron microscope. The hydrothermally synthesized electrode obtained specific capacity (Qs) of 434.16C/g at 1.6 A/g compared to its counterpart. Owing to maximum capacity, this electrode was assembled in two electrode configurations to explore their hybrid performance. The NiS//AC results in Qs of 261.6C g−1 at 1.5 A/g with great capacity retention of 86.7 % after testing for 10,000 GCD cycles. Furthermore, the device has revealed astonishing specific energy of 61.76 Wh/kg and power of 1275 W/kg. These experimental outcomes were investigated by using the Dunn's model to extract the capacitive part from the diffusive, demonstrating the nature of (NiS//AC) hybrid device. Moreover, Power's law was employed to validate the assembled device behavior by evaluating b values. In sum, it appears promising to utilize the suggested NiS//AC with elevated performance and great stability as anode material in hybrid supercapacitors.

Facile Solvothermal Synthesis of NiO/g-C3N4 Nanocomposite for Enhanced Supercapacitor Application

There is a desperate demand for efficient energy storage systems to fulfill future energy demands. Herein, we exemplify a facile solvothermal approach followed by heat treatment to synthesize NiO/g-C3N4 nanocomposites for enhanced supercapacitor applications. The molar ratio of g-C3N4 is varied to achieve numerous nanostructures like nanoparticles and nanorods with optimum specific capacitance. Further, all as-prepared electrode materials are examined for supercapacitor application. The electrochemical behavior of prepared NiO/g-C3N4 nanocomposites is carried out under cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode cell under different electrolytes such as aqueous sodium sulphate electrolyte (1.0 M Na2SO4) and potassium hydroxide electrolyte (3.0 M KOH). Among all the electrode materials, NO-4 (1 : 2) shows the highest specific capacitance of 338.68 F/g at a scan rate of 2 mV/s and 161.3 F/g at a current density of 1 A/g in 1.0 M Na2SO4 electrolyte. Also, this electrode material shows 95.22 F/g at a scan rate of 2 mV/s in 3.0 M KOH electrolyte. The excessive specific capacitance of this electrode material is due to retarded charge transfer resistance in the interface at the electrode and electrolyte and a increased number of active sites. The investigation of the electrokinetics of all the prepared electrodes was also carried out, and it revealed the charge storage contribution of capacitive and diffusive parts which levitates the higher specific capacitance. The two-electrode study for evaluating supercapacitor performance is studied. The NO-4//NO-4 SSD in 1.0 M Na2SO4 electrolyte shows 18.23 F/g at a specific capacitance of 1 A/g with a corresponding energy density of 10.13 Wh/kg and a power density of 1.01 kW/kg, respectively.

Dual-Mode Stretchable Sensor Array with Integrated Capacitive and Mechanoluminescent Sensor Unit for Static and Dynamic Strain Mapping

Electronic skin (e-skin) has the potential to detect large-scale strain, which is typically achieved by integrating multiple strain sensors into an array. However, the latency and limited resolution of sensing have hindered its large-scale sensing applications. Here, we have developed a high-resolution detection sensing system capable of detecting static and dynamic strain with a simple fabrication process by combining capacitive and mechanoluminescent (ML) sensor units. An elastic polydimethylsiloxane (PDMS) composite film doped with ZnS:Cu and BaTiO3(BT) particles are fabricated as the functional film of the capacitive sensor. In contrast, the transparent electrode was fabricated on the surface of the as-prepared film. By incorporating BT nanoparticles into the elastic substrate, the ML intensity of the ZnS:Cu was improved up to 2.89 times that without BT addition, and the sensitivity of the capacitive sensor was increased as well. The capacitive part of the sensor presented a GF of 0.9 and good stability, while the ML part exhibited excellent performance, making it suitable for both static and dynamic sensing. Furthermore, the strain sensor integrated by 10 × 10 sensing units is demonstrated to detect large-scale strain with high resolution. Moreover, finger joint strain distribution tracking is achieved by attaching the strain sensor unit to the finger joint. With these characteristics, the e-skin may have great potential for bio-motion monitoring and human-computer interaction applications.

Dual‐Mode Pressure Sensor Integrated with Deep Learning Algorithm for Joint State Monitoring in Tennis Motion

The precise capture and identification of movement features are important for numerous scientific endeavors. In this work, we present a novel multimodal sensor, called the resistance/capacitance dual‐mode (RCDM) sensor, which effectively differentiates between compression and stretchable strains during tennis motion; meanwhile, it can also accurately identify various joint movements. The proposed wearable device features a seamless design, comprising two separate components: a resistive part and a capacitive part. The resistive and capacitive components operate independently and utilize a resistance–capacitance mechanism to measure pressure and strain signals, respectively. The RCDM sensor demonstrates remarkable sensitivity to strains (GF = 7.84, 0%–140%) and exceptional linear sensitivity (S = 4.08 kPa−1) through capacitance. Utilizing machine learning algorithms, the sensor achieves a recognition rate of 97.21% in identifying various joint movement patterns. This advanced production method makes it feasible to manufacture the sensors on a large scale, offering tremendous potential for various applications, including tennis sports systems.

МОДЕЛИРОВАНИЕ ЕМКОСТНОГО ДАТЧИКА ДЛЯ РЕГИСТРАЦИИ ЧАСТИЧНЫХ РАЗРЯДОВ В СИЛОВОМ КАБЕЛЕ

The article discusses the simulation of a partial discharge (PD) pulse in a power single-core coaxial cable using a capacitive sensor. The sensor provides capacitive coupling to the test sample and its capacitive element is in fact part of the total capacitance of the cable. The resistive element added to the design makes it possible to register current pulses of partial discharges. At the same time, the used sensor has no connection with high-voltage electrodes of the systems, which is its undoubted advantage in comparison with conventional capacitive sensors.

High-Frequency Capacitor with Working Substance "Insulator-Undoped Silicon-Insulator"

The study of the parameters of capacitors with various working substances is of interest for the design and creation of electronic elements, in particular for the development of high-frequency phase-shifting circuits.The purpose of the work is to calculate the high-frequency capacitance of a capacitor with the working substance "insulator-undoped silicon-insulator" at different applied to the capacitor direct current (DC) voltages, measuring signal frequencies and temperatures.A model of such the capacitor is proposed, in which 30 µm thick layer of undoped (intrinsic) crystalline silicon (i-Si) is separated from each of the capacitor electrodes by 1 µm thick insulator layer (silicon dioxide).The dependences of the capacitor capacitance on the DC electrical voltage U on metal electrodes at zero frequency and at the measuring signal frequency of 1 MHz at absolute temperatures T = 300 and 400 K are calculated. It is shown that the real part of the capacitor capacitance increases monotonically, while the imaginary part is negative and non-monotonically depends on U at the temperature T = 300 K. An increase in the real part of the capacitor capacitance up to the geometric capacitance of oxide layers with increasing temperature is due to a decrease in the electrical resistance of i-Si layer. As a result, with an increase in temperature up to 400 K, the real and imaginary parts of the capacitance take constant values independent of U. The capacitance of i-Si layer with an increase in both temperature T and voltage U is shunted by the electrical conductivity of this layer. The phase shift is determined for a sinusoidal electrical signal with a frequency of 0.3, 1, 10, 30, 100, and 300 MHz applied to the capacitor at temperatures 300 and 400 K.

Relationship between Dielectric Relaxation Time and Permeability of High-Rank Coal in the Jiaozuo Mining Area.

To evaluate the permeability of coal by the complex resistivity method, the real part of complex resistivity (R), the imaginary part of complex resistivity (X), capacitance (C), permeability (k), and strain (ε) of coal in different directions under variable pressure were measured. Based on the physicochemical structure characteristics of coal and its conductivity and dielectric mechanism, the experimental phenomenon was analyzed and correlated with the permeability of coal. The results demonstrated that (1) the R-X curve is U-shaped. With increasing frequency, the amplitude first decreases and then increases, forming an obvious trough. C decreases with increasing frequency. (2) The R-X curve is affected by pressure and directivity. The absolute value of the R-X curve amplitude gradually decreases and shifts to the left as the pressure increases; meanwhile, it decreases and shifts to the left in the order of the vertical bedding direction (z direction), the vertical main fracture direction in parallel bedding (y direction), and the main fracture direction in parallel bedding (x direction). There is also a related change law for C. (3) The dielectric relaxation time (τ) was optimized as the electrically sensitive parameter of coal. τ continues to decrease as pressure increases and decreases in the order of the z, y, and x directions. (4) The permeability of coal is strongly correlated with the dielectric relaxation time, and the relationship between them conforms to a logarithmic function. The relationship of strain and the dielectric relaxation time verifies the strong correlation between permeability and the dielectric relaxation time. This study provides an experimental basis and theoretical support for the subsequent accurate prediction and evaluation of coal permeability using the dielectric relaxation time.

VHF/UHF Ultrawideband Slim Monopole Antenna With Parasitic Loadings

A slim monopole antenna with novel parasitic loadings is presented in this letter. The proposed antenna consists of three metal strips, including a monopole strip and two parasitic strips on both sides, which is installed on a box that served as ground. Compared with traditional open sleeve monopole antennas, novel in-body structures are added to the three strips to achieve wider impedance and radiation pattern bandwidths. The in-body structures are composed of two parts, the inductive part (realized by etching a thin strip on the lower tip of the main strip) and the capacitive part (formed by adding a rectangular plate to the lower tip of the main strip). The prototype of the proposed antenna has been manufactured and measured. The bandwidth with VSWR ≤ 3:1 is 220–950 MHz (center frequency is 585 MHz), 4.3 octaves, which partly covers very high frequency (VHF) and ultrahigh frequency (UHF) bands. The gain is greater than −2.4 dBi. The antenna owns omnidirectional radiation patterns in the whole working band. With the thickness of the prototype being only 50 mm, it is suitable for the applications of backpacked radio stations and GSM communications.

Structure and Circuit Engineering Features of Stand- Alone Photovoltaic System with a Battery-Capacitive Energy Storage Device

The purpose of this research is to analyze the structure and circuit design of stand-alone photovoltaic system with a battery-capacitive energy storage device to ensure voltage stability under peak voltage and a variable nature of the power generated by a solar panel. There is an original active control scheme for a hybrid drive. The peak power of the solar panel was 100 W. The battery part of the energy storage device was represented by a 12 V gel lead-acid battery with a charging capacity of 11 Ah, and the capacitive part consisted of a battery of supercapacitors with an electrostatic capacity of 80 F, an operating voltage of 15.5 V. A rheostat was used as a load during a stationary discharge of the storage device with a resistance of 12 Om, and the pulsed nature of the discharge was simulated using an automobile air compressor. The analysis of circuit design variants that implement the charging process the capacitive part of the energy storage device from a solar panel directly or with a shunt DC/DC converter is performed. Charging and discharging of the battery part was controlled by the ProStar-15 controller. In both cases, charging buffer modes the battery and capacitive parts of the energy storage device were used. The research results have identified ways to increase the stability of the output voltage under peak voltage and the variable nature of electricity generation conditions while increasing the resource of an expensive battery.

A lumped parameter model to evaluate the relevance of excess air as a tracer of exchanged flows between transmissive and capacitive compartments of karst systems

The objective of this study was to evaluate the relevance of using excess air (EA) for the characterization of drain/matrix exchange in karst systems using a rainfall discharge model coupled with the simulation of EA measured at the outlet of the studied system. The conceptual model assumes a linear relationship between the formation of EA and the increase of hydrostatic pressure in the capacitive part of the aquifer. The simulated EA at the spring consists of the mixing of water circulating in the different compartments of the aquifer, with their own EA signature. The analysis is performed taking as an example the Durzon karst system (Larzac, France). The modeling is applied using daily rainfall discharge time series and 18 EA measurements at the main outlet of the karst system within 3 hydrological cycles. The main modeling results show that EA variations measured at the karst spring can be explained by recharge processes and exchange between conduit and matrix. EA measurements at the spring thus contain valuable information about the flow dynamics within the aquifer. Furthermore, results show that the use of EA measurements, despite their sparse temporal resolution, allows for reducing uncertainties in the estimation of some parameters of the reservoir model used for the simulation of karst spring discharge.

Fixed-Switching-Frequency Background Capacitor-Current-Sensor Calibration for DC–DC Converters

Background capacitor-current-sensor (CCS) calibration (CAL) is proposed for dc-dc converters to achieve fast load-transient response for small undershoot ${V_{{US}}}$ , overshoot ${V_{{OS}}}$ , and short settling time ${t_{{S}}}$ in the output voltage ${V_{{O}}}$ . The CCS' impedance ${Z_{{Cs}}}$ is calibrated to a scaled replica of the output capacitor's impedance ${Z_{{Co}}}$ , which varies with printed-circuit-board parasitics, process-voltage-temperature variations, and aging. Thus, the CCS shunts a current ${I_{{Cs}}}$ equal to a scaled output-capacitor current ${I_{{Co}}}$ , which instantly and accurately reflects load-current ${I_{{load}}}$ transients. The CAL operates at a fixed switching frequency ${f_{{SW}}}.$ At this ${f_{{SW}}}$ , although ${Z_{{Cs}}}$ is dominated by its inductive part, this work can still calibrate its capacitive and resistive parts based on the time derivatives dV ${_{{O}}}/dt$ and dI ${_{{Cs}}}$ /dt, respectively. This fixed- ${f_{{SW}}}$ CAL overcomes the bottleneck of the prior state-of-the-art CCS CAL, which must hop ${f_{{SW}}}$ to lower values to calibrate ${Z_{{Cs}}}$ capacitive and resistive parts, thereby enlarging ${V_{{O}}}$ steady-state ripples and transient fluctuations during CAL. Thus, only this fixed- ${f_{{SW}}}$ CAL is suitable for background operation. Moreover, this CAL can be interrupted by a load-transient or dynamic-voltage-scaling event and be reactivated in quasi-steady state. The shortest CAL period is 8.8 μ s at ${f_{{SW}}$ = 30 MHz without interruption. A buck converter with this CCS CAL is fabricated in 0.18-μ m CMOS process and occupies 2.25 mm². Under a 2-A/4-ns step-up (step-down) load transient, the measured ${V_{{US}}}$ ( ${V_{{OS}})}$ and ${t_{{S}}}$ are 36 mV (29 mV) and 56 ns (45 ns), respectively. Compared with prior state of the arts, this work achieves much smaller ${V_{{O}}}$ ripples and fluctuations during CAL, shorter CAL period, and faster load-transient response.

Charging and Discharging Characteristics of a Battery-Capacitive Energy Storage Device for Stand-Alone Photovoltaic System

The purpose of the research is to study the charging-discharging characteristics of a hybrid energy storage device which consists of two parallel connected battery and capacitive parts to assess the work efficiency of its circuit design as a part of standalone photovoltaic system. The charge current kinetics of a hybrid storage device from a solar panel was carried out under natural conditions at a specific power of incident solar radiation of 800–850 W/m2. The discharge current kinetics of battery and capacitive storages were obtained with a resistive load and disconnected solar battery. The dynamics of charging and discharging processes of the battery and capacitive parts of the energy storage device were monitored by the voltage rise/fall rate. The battery part of the drive is charging and starting the device based on a lead-acid gel battery with a charging capacity of 11 A·h, 12.8 V maximum voltage, and 15 A maximum discharge current. The capacitive part consisted of a new generation INSPECTOR Booster supercapacitor starting the device with an electrostatic capacity of 80 F, 15.5 V voltage, and 800 A starting current. As the energy source a solar battery was used, with a 12 V nominal voltage and 100 W peak power. A 6 Om rheostat with 15 A consumption current was used as a load during the storage device discharge. A Morningstar ProStar-15 charging/discharging controller with a pulse-width modulation function was used to monitor and control the photovoltaic system. Quantitative charging and discharging characteristics of a battery-capacity energy storage device were obtained for the use in the development of standalone photovoltaic system.

Electrical Impedance-Based Characterization of Hepatic Tissue with Early-Stage Fibrosis.

Liver fibrosis is a key pathological precondition for hepatocellular carcinoma in which the severity is confidently correlated with liver cancer. Liver fibrosis, characterized by gradual cell loss and excessive extracellular matrix deposition, can be reverted if detected at the early stage. The gold standard for staging and diagnosis of liver fibrosis is undoubtedly biopsy. However, this technique needs careful sample preparation and expert analysis. In the present work, an ex vivo, minimally destructive, label-free characterization of liver biopsies is presented. Through a custom-made experimental setup, liver biopsies of bile-duct-ligated and sham-operated mice were measured at 8, 15, and 21 days after the procedure. Changes in impedance were observed with the progression of fibrosis, and through data fitting, tissue biopsies were approximated to an equivalent RC circuit model. The model was validated by means of 3D hepatic cell culture measurement, in which the capacitive part of impedance was proportionally associated with cell number and the resistive one was proportionally associated with the extracellular matrix. While the sham-operated samples presented a decrease in resistance with time, the bile-duct-ligated ones exhibited an increase in this parameter with the evolution of fibrosis. Moreover, since the largest difference in resistance between healthy and fibrotic tissue, of around 2 k, was found at 8 days, this method presents great potential for the study of fibrotic tissue at early stages. Our data point out the great potential of exploiting the proposed needle setup in clinical applications.