Line Circuit Research Articles

Ka‐band distributed microelectromechanical systems transmission line phase shifter using metal air metal switch

AbstractA new approach for designing a two‐state unit cell for a six‐bit distributed coplanar waveguide microelectromechanical systems (MEMS) phase shifter is proposed in this study. The proposed structure includes metal air metal (MAM) capacitors as switches and consists of a unit cell with one MEMS and two MAM switches to produce two phase shifts per unit cell. In the first state, the MAM switches are pulled down and a 5.625° phase shift is achieved, and in the second state, the MEMS switch is actuated to yield a phase shift of 11.25°. The designed structure is modeled using equivalent transmission line circuit model and simulated in the Ka‐band at 34 GHz, employing advanced design system (ADS), ANSOFT HFSS and COMSOL software. Based on the modeling and simulation results, the root‐mean‐square (RMS) phase error is 1.4°, and maximum return loss and minimum insertion loss for all 64 states are better than −10.1 and −1.45 dB, respectively. The main advantages of the designed structure are its small size, low loss, low phase error and a simple phase shift mechanism. A fabrication process is also proposed for the distributed MEMS transmission line (DMTL) phase shifter that shows the feasibility of the proposed design. The proposed structure can be easily scaled to other bands and used in applications with more bits as complex as phased array antennas.

Analysis of strain sensitivity under flexural load of 3D printed carbon nanotube-doped epoxy circuits

A 3D printing system able to print circuits of conductive epoxy resin doped with carbon nanotubes (CNTs) is proposed. Different simple circuits, more specifically lines and strain gauge patterns, made of resins reinforced with 0.3, 0.5, 0.8 and 1 wt% of CNTs were printed on the surface of glass fiber laminates. It was observed that increasing the CNT content reduced the wettability of the printed circuits on the glass fiber substrate. In every case the contact angle was far below 90°. Furthermore, the strain sensing capabilities were analyzed under a flexural load. The results showed that the sensitivity increased with CNT content (with gauge factor values from 1.5 to 2.5) as a result of the prevalent effect of well-dispersed areas due to a reduction in the tunneling distance. On the other hand, the strain gauges showed a lower sensitivity (around 20%–40% less, depending on the condition) compared with line circuits due to localized compressive effects. Furthermore, good repeatability of the strain sensors was proved during cycling tests, with similar baseline and peak values for the electrical resistance in each cycle. Therefore, the proposed materials have a high potential for applications in structural health monitoring.

Bridging physics-based and equivalent circuit models for lithium-ion batteries

In this article, a novel implementation of a widely used pseudo-two-dimensional (P2D) model for lithium-ion battery simulation is presented with a transmission line circuit structure. This implementation represents an interplay between physical and equivalent circuit models. The discharge processes of an LiNi0.33Mn0.33Co0.33O2-graphite lithium-ion battery under different currents are simulated, and it is seen the results from the circuit model agree well with the results obtained from a physical simulation carried out in COMSOL Multiphysics, including both terminal voltage and concentration distributions. Finally we demonstrated how the circuit model can contribute to the understanding of the cell electrochemistry, exemplified by an analysis of the overpotential contributions by various processes.

Smart scheduling of transmission line switching: optimization of multi-objective microgrid’s day-ahead energy scheduling with considering high penetration of green energies and INVELOX

In recent years, distributed generation resources, especially renewable energies, have utilized in different situations; to solve the environmental pollution problems and lack of sufficient energies. In this regard, microgrid’s bi-objective energy scheduling and management are considered with INVELOX wind turbine, micro-turbine, boiler, CHP, photovoltaic, wind turbines, and also energy storage systems to enhance the reliability of the network. Moreover, portable resources have been used to manage the demand side. The remarkable innovation of this paper is to control the transmission line circuit breakers, and as a result, control the ecological contamination and microgrid’s cost; by variation in exchangeable power. In this strategy, the microgrid is capable of changing the tie line capacity and achieve the top-selling or buying electricity to/from the power system by switching the circuit breakers (circuit breakers can switch by operator decision or smart devices if required, at all-time intervals). The proposed strategy is modeled as mixed-integer linear programming. All-out expense and ecological contamination of under-study’s microgrid are considered as the objective function. The EPC technique and fuzzy methodology have been used to tackle the problem and select the ideal arrangement and solution, respectively. The outcomes display the improvement of microgrid operation with the presented energy management strategy, so that cost decreased by about 48.76% and 38.6%, in the last two scenarios, respectively.

Hydrogen-doped viscoplastic liquid metal microparticles for stretchable printed metal lines.

Conductive and stretchable electrodes that can be printed directly on a stretchable substrate have drawn extensive attention for wearable electronics and electronic skins. Printable inks that contain liquid metal are strong candidates for these applications, but the insulating oxide skin that forms around the liquid metal particles limits their conductivity. This study reveals that hydrogen doping introduced by ultrasonication in the presence of aliphatic polymers makes the oxide skin highly conductive and deformable. X-ray photoelectron spectroscopy and atom probe tomography confirmed the hydrogen doping, and first-principles calculations were used to rationalize the obtained conductivity. The printed circuit lines show a metallic conductivity (25,000 S cm-1), excellent electromechanical decoupling at a 500% uniaxial stretching, mechanical resistance to scratches and long-term stability in wide ranges of temperature and humidity. The self-passivation of the printed lines allows the direct printing of three-dimensional circuit lines and double-layer planar coils that are used as stretchable inductive strain sensors.

Experimental study of a double-circuit optoelectronic generator of radio-frequency signals

An urgent issue is the development of radio frequency generators operating in the microwave range, with high frequency stability, wide tuning band, as well as small size and weight. Microwave signal generators are used as part of radio electronic devices and devices for telecommunication, radio navigation and metrological purposes; therefore, improving their main characteristics is an important goal for the further development of radio electronic devices. A technological feature of optoelectronic generators is the combined use of solid-state components of modern HF and UHF optoelectronics, fiber optics and traditional components of UHF/EHF technology. According to the principle of operation and construction scheme, the optoelectronic generator is similar to the classic radio-frequency self-oscillator with a delay line in the feedback circuit. A feature of its work is the multifrequency nature of the generated oscillations, for which the conditions for amplitude balance and phase balance are satisfied. In the case of an optoelectronic generator, a feedback ring with a resonant system and a delay element is made using a single-mode fiber of a certain length. The signal delay time in the feedback loop is a significant parameter of the optoelectronic generator, which affects the noise and spectral characteristics of the generator. With an increase in the length of the fiber-optic path, the delay time in the feedback loop increases, thereby reducing the level of frequency noise. However, with an increase in the length of the fiber-optic path, the distance between adjacent modes of the optoelectronic oscillator also decreases, increasing the requirements for the bandwidth of the band-pass filter. The solution to this problem was the use of a multi-circuit optoelectronic generator. The paper considers a model created by the authors for a two-circuit optoelectronic generator with fiber-optic paths 1000 m and 30 m long. The available element base did not allow to reduce the generator's weight and dimensions. On this model, the characteristics of the circuit elements have been experimentally studied. The spectral characteristics of the generator have been estimated theoretically, which are in good agreement with the results of practical research. Phase noise is an important parameter in generator evaluation. Oscillators used as reference and measuring oscillators must certainly have a high frequency stability of the generated signal. Oscillations in autogenerators arise due to the effect of intrinsic noise in the circuit elements, which is one of the reasons for the occurrence of noise in the spectrum of the generator output signal. Intrinsic noise includes thermal, shot and flicker noises in semiconductor elements of generators. The article calculates the power spectral density of the phase noise of a single-loop oscillator and a dual-loop oscillator, which confirmed the assumption about a compromise between the noise level and the requirement for the filter bandwidth in a single-loop optoelectronic oscillator. An important advantage of optoelectronic generators, in comparison with generators built according to classical circuitry, is the absence of a compromise between the frequency tuning band of the device generation and the level of frequency noise.

Investigation of resonance phenomena in power lines supplying powerful rectifier plants

A feature of modern power supply systems is the presence of a large number of electrical devises that consume non-sinusoidal current. The examples of the devices are frequency converters or rectifiers of large unit power. But substations for supplying a group of variable frequency drives affect negatively also. Since the equivalent circuit of the power includes line inductive and capacitive elements, under certain conditions, resonant can occur in the power supply system. The model for studying a power supply system with a powerful rectifier load has been developed in the MATLAB + Simulink environment. The equivalent power line circuit is adopted in the form of a certain number of series-connected sections. The number of sections was chosen from the condition of obtaining information about all harmonics, which the electric power quality standard prescribes to analyze. The simulation results show the number of the harmonic at which the resonance occurs depends on the length of the power line. It has been found that at resonance, the maximum current harmonic circulates through the source. And at the end of the line in this moment, the current harmonic has a minimum value, while the corresponding voltage harmonic rises sharply.

Study on icing and its trip laws of transmission lines in Shanxi Power Grid

Overhead transmission lines are important carriers of electric energy transmission. Their icing, galloping and shedding in winter and spring seriously threatened the safe operation of Shanxi power grid. Especially in the recent years, compact lines and double circuit lines on the same tower, typical types of overhead transmission lines in Shanxi Power Grid, were affected by frequent trips induced by icing, galloping, and shedding appeared in their conductors repeatedly, which seriously reduced the capacity of power energy transmission in Shanxi and caused trillions of power load losses. Through detailed investigation and analysis of the characteristics and historical fault cases of compact lines and double circuit lines on the same tower in Shanxi Power Grid, the key causes and main laws of two types of lines in Shanxi Power Grid are clarified, which could provide support for the follow-up line anti-ice technical transformation and capacity improvement.

Methodology to calculate the intensity of the electric field generated in a double circuit High Voltage Alternating Current overhead transmission line

One of the parameters considered in the design of transmission lines is the distribution of its generated electric field. The following article presents a reference methodology that allows obtaining the electric field on the right-of-way of a High Voltage Alternating Current (HVAC) overhead transmission line, the methodology is developed based on the Load Simulation Method (MSC) and the Image Method. The results obtained present a difference of less than 2%. In this way a case study of a 230 kV HVAC double circuit transmission line presented, an optimization of the phases of the transmission line circuits is carried out to determine the most efficient configuration for obtaining the electric field density. The results obtained allow a configuration of n circuits, admitting the different nominal voltages of the HVAC lines.

Transmission Line Fault Identification Using ANN and Time-Domain Measurements at Local Bus (Dept.E)

Among many applied techniques for overhead transmission line fault recognition, the artificial neural networks-aided schemes have demonstrated superior efficacy. This paper presents two methods based on time domain measurements at the local end of the transmission line to identify the single circuit line fault type for low impedance faults. The first deals with time samples of the current and voltage waveforms of the three phases during the fault. The second uses the measured mms values of currents and voltages. The latter can also determine the fault location on the line. It is also extended to produce the faulty circuit and fault type of double circuit lines for low impedance faults. Furthermore, the paper proposes a new algorithm for diagnosing the single line high impedance fault. A modified version of the algorithm is also developed to obtain a good representative feature vector with the least possible elements. The modification has enhanced diagnosing capabilities and can classify the high impedance faults. This enables the fast and accurate recognition of the faults that is a necessary request for the digital relaying system. The design and training of the decision making ANN for each approach are described. The studied techniques are tested with many cases to assess their diagnostic capabilities. Besides, the performance of the competitive methods is compared.

Design and analysis of ultrathin X‐band frequency selective surface structure for gain enhancement of hybrid antenna

A wideband ultrathin frequency selective surface (FSS) structure is designed and developed for the complete X-band. The design employs a metallic tetra-arrow (two bidirectional arrows placed diagonally) and a circular split structure (metallic) in the top side and bottom side of RT duroid 5880LZ low-loss substrate respectively. The proposed design has novel contribution in terms of significant reduction in electrical thickness (0.007λ0 which is corresponding to lowest operating frequency, 8.3 GHz) and wider transmission (S21) bandwidth (measured: S21 ≤ − 10 dB, 8.15-13.2 GHz, 47.3%), covering entire X-band due to cumulative loading of surface mount chip resistors in the top layer. The principle of operation of the proposed FSS further can be justified with its equivalent transmission line circuit model, which is based on microwave filter (band-stop and band-pass) topology for anticipating the desired characteristics. The FSS structure is further integrated with dielectric resonator (DR)-slot hybrid antenna for enhancing the gain (measured: peak gain of 4.5 dBi without FSS and 7.8 dBi with FSS) of the antenna. The proposed FSS structure is fabricated and measured performance has very similar responses as simulated ones.

Evaluation of the Prothrombin Fragment 1.2 in Patients with COVID-19

Introduction: Coronavirus disease 2019 (COVID-19) may cause a hypercoagulable state. The D-dimer is frequently elevated in COVID-19, but other markers of coagulation activation, including the prothrombin fragment 1.2 (PF1.2) are poorly described. Given the near universal D-dimer elevation in critically ill patients with COVID-19, the PF1.2 may be a more specific marker to identify thrombotic complications.Methods: We studied hospitalized adults with COVID-19 and PF1.2 measurement performed at any point during hospitalization. We evaluated the relationship between PF1.2 and synchronously measured D-dimer. We utilized receiver operating characteristic (ROC) analysis to evaluate optimal thresholds for diagnosing thrombosis and multivariable logistic regression to evaluate association with thrombosis. Thresholds for each assay for multivariable regression were determined from ROC analysis. To avoid confounding of therapeutic anticoagulation on PF1.2 or D-dimer measurement, patients receiving therapeutic anticoagulation at the time of assay measurement were excluded from these analyses.Results:Patients and Thrombotic Events. 115 hospitalized patients with COVID-19 were included [110 (95.7%) critically ill], encompassing 3318 patient-days (474 patient-weeks) analyzed for thrombotic and critical illness complications. At the data cutoff date, 74 patients (64.3%) had been discharged from the hospital alive, 24 patients (20.9%) died in the hospital, and 17 patients (14.8%) remained hospitalized, having been hospitalized for a median of 44 (range, 30-62) days. Over a median follow-up of 29 (range, 2-62) hospital days, 26 patients developed radiographically-confirmed VTE (22.6%, a rate of 5.49 per 100 patient-weeks); including arterial, extracorporeal circuit, and recurrent line thrombosis, 56 patients (48.7%) developed a thrombotic complication. At the time of PF1.2 and synchronous D-dimer measurement, 37 patients (32.1%) were receiving therapeutic anticoagulation, 77 patients (67.0%) were receiving prophylactic anticoagulation, and 1 patient (0.9%) was not receiving pharmacologic thromboprophylaxis.Association of PF1.2 with D-dimer. Synchronously measured PF1.2 and D-dimer were moderately positively correlated (r=0.542, P<0.001, Figure 1) but significant discordance was observed in elevation of each marker above the laboratory reference range (59.0% patients with elevated PF1.2 vs. 98.5% elevated D-dimer).Association of PF1.2 with Hypercoagulability. Median PF1.2 levels were higher in patients with thrombosis than those without (611 vs. 374 pmol/L, P=0.006, Figure 2). Therapeutic anticoagulation suppressed median PF1.2 levels: median (IQR) PF1.2 in patients not receiving therapeutic anticoagulation (N=29) was 611 pmol/L (333-1148 pmol/L), significantly higher than the median (IQR) PF1.2 in patients receiving therapeutic anticoagulation (N=27) of 347 pmol/L (195-506 pmol/L), P=0.0017.ROC and Multivariable Regression Analyses. In ROC analysis, PF1.2 had superior specificity and conferred a higher positive likelihood ratio in identifying patients with thrombosis than did the D-dimer (PF1.2 threshold of >523 pmol/L: 69.2% sensitivity, 67.7% specificity; >924 pmol/L: 37.9% sensitivity, 87.8% specificity, Figure 3). In multivariable analysis controlling for age, sex, and BMI, a PF1.2 >500 pmol/L was significantly associated with VTE [adjusted odds ratio (OR) 4.26, 95% CI, 1.12-16.21, P=0.034] and any thrombotic manifestation (adjusted OR 3.85, 95% CI, 1.39-10.65, P=0.010); conversely, synchronously measured D-dimer >2,500 ng/mL was not significantly associated with VTE (OR 5.91, 95% CI, 0.69-50.56, P=0.11) or any thrombotic manifestation (OR 2.47, 95% CI, 0.78-7.78, P=0.12). The vast majority (90.6%) of patients with a non-elevated PF1.2 result did not develop VTE and 75% did not develop any thrombotic complication.Conclusions: When measured at any point during hospitalization in patients not receiving therapeutic anticoagulation, PF1.2 was more specific than synchronously measured D-dimer in identifying patients who experienced thrombosis and was significantly associated with thrombotic manifestations in multivariable analyses while the D-dimer was not. PF1.2 may be a useful assay, and potentially more discriminant than D-dimer, in identifying thrombotic manifestations in hospitalized patients with COVID-19.DisclosuresAl-Samkari:Rigel: Consultancy; Agios: Consultancy, Research Funding; Argenx: Consultancy; Amgen: Research Funding; Dova: Consultancy, Research Funding. Kuter:Caremark: Consultancy, Honoraria; Immunovant: Other: Travel Expenses, Research Funding; CRICO: Consultancy, Honoraria; UCB: Consultancy, Honoraria; Up-To-Date: Consultancy, Honoraria, Patents & Royalties; Zafgen: Consultancy, Honoraria; Sanofi (Genzyme): Consultancy, Honoraria; Shionogi: Consultancy, Honoraria; Shire: Consultancy, Honoraria; Shionogi: Consultancy; Protalix Biotherapeutics: Consultancy; Principia: Consultancy, Research Funding; Protalex: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Alnylam: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Agios: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Daiichi Sankyo: Consultancy, Honoraria; Actelion (Syntimmune): Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Argenx: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Kezar Life Sciences, Inc: Other, Research Funding; Platelet Disorder Support Association: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Momenta: Consultancy, Honoraria; Merck Sharp Dohme: Consultancy, Honoraria; Rigel: Consultancy, Honoraria, Other, Research Funding; Takeda (Bioverativ): Consultancy, Honoraria, Other, Research Funding; Dova: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria; Immunovant: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Kyowa-Kirin: Consultancy, Honoraria; Protalex: Consultancy, Honoraria, Other, Research Funding; Principia Biopharma: Consultancy, Honoraria, Other, Research Funding. Rosovsky:Bristol-Myers Squibb, Dova, Janssen, Portola: Consultancy; Bristol-Myers Squibb, Janssen: Research Funding.

Data Encoding Improvement and Size Reduction of Chipless RFID Tag Using Short-circuit Line Effect and Angle-based Divided Loops

This paper focuses on a short circuit and concentric loop effects to improve the structure dimension as well as enhance the ability to encode electromagnetic wave data for chipless RFID tags. The tag is composed of star-shaped rings that are concentrically nested together. The following factors help reduce the tag size: using the phenomenon of electromagnetic backscattering, assessment by the Radar Cross Section (RCS), the antenna-free tag only includes the multi-frequency resonators. By inserting short circuit lines combined with concentric loops, the number of resonant peaks increases exponentially without increasing the tag overall dimension. In addition, by inserting the short circuit lines at different angles between the two consecutive loops, we can adjust the resonant frequency in the frequency bands, thereby changing the value of the bit by shifting the frequency position. The overall dimension of the resulted tag is 13mmx13 mm and the tag is aimed to be a printable tag on the flexible substrate to minimize the fabrication cost. With the 18-vertex star-shaped tag with five concentric loops, this chipless RFID tag can encode up to 16 bits with high resolution and large data density.

Comparing Novel MMIC and Hybrid Circuit High Efficiency GaAs Schottky Diode mm-Wave Frequency Doublers

A novel Schottky diode frequency doubler in E-band, using biased series-connected diodes in the output waveguide, is reported. The doubler was implemented using a GaAs Schottky Monolithic Microwave Integrated Circuit (MMIC) process with integrated capacitors and beam leads. A comparison is made with a hybrid doubler using a more conventional single-ended configuration with two discrete diodes in a planar transmission line circuit. Both devices exhibit excellent performance over the 67–78 GHz design bandwidth, with the novel MMIC design producing 25 to 55 mW at 12 to 22% power conversion efficiency. Good agreement of measurements with simulations was also found.

A Note on Branch Flow Models With Line Shunts

When the shunt elements in the $\Pi$ circuit line model are assumed zero, it has been proved that branch flow models are equivalent to bus injection models and that the second-order cone relaxation of optimal power flow problems on a radial network is exact under certain conditions. In this note we propose a branch flow model that includes nonzero line shunts and prove that the equivalence and the exactness of relaxation continue to hold under essentially the same conditions as for zero shunt elements.

Assessment of MOV dimensioning principles, TRV risk management and cost-effectiveness of gapless FSC in Finnish series compensated system by utilizing EMT simulations

Between years 1997 and 2016 eleven fixed series capacitors (FSCs) have been built to enhance the interarea transmission capability of Finnish 400 kV transmission system. During these years, Fingrid (Finnish transmission system operator) has experienced various reliability issues with the existing FSCs. In early 2017 Fingrid launched a development project with target to improve the reliability and cost-effectiveness of Fingrid’s FSC fleet by developing the FSC specification, project and maintenance practices. As a part of the project, possibilities to develop FSC overvoltage protection requirements were studied for more robust, reliable and cost-effective technical solution. To compare investment costs and risks of FSC protection with and without forced triggered spark gap, an extensive EMT study was carried out. The study consisted of MOV energy and TRV-risk assessments including extensive sensitivity analysis covering 11 existing and 2 new FSC installations. Based on results of the study, new improved MOV dimensioning principles and the line circuit breakers’ TRV requirements were established to address for future FSC investments and refurbishments.

ELECTROMAGNETIC INTERFERENCE (EMI) PRODUCED BY HIGH VOLTAGE TRANSMISSION LINES

Electromagnetic interference in high voltage transmission lines has been an interest topic due to its effect on human health, plants, electrical and telecommunication equipment. Extremely high voltages (EHV) in transmission lines are reasons of electrostatic effects, while short circuit currents and line loading currents are responsible for electromagnetic effects. The aim of this research is to analyze electromagnetic fields in high voltage transmission lines in theoretical study and calculating its level in overhead T. L and therefore estimated the EMI produced, by employing a mathematical model of 230 KV tower double circuit configurations of high voltage transmission lines. The calculation is based on computer aided analysis (CAA) by using fields and corona effects software (FACE). It's found that the overhead power lines of general frequency (50 Hz) generates a highly intense magnetic field, the electromagnetic fields depends on the distance from sources and the type of line configuration. They decrease as the distance increase from the tower and conductors and increase with a high current. The strength of an electric field is proportional to the voltage of the line and the magnetic field strength is proportional to the current in the high voltage transmission lines. Distribution line with a high current load may produce a magnetic field that is as high as those produced by some high voltage transmission lines. Some techniques of reduction of the effects of electromagnetic interference have suggested such as rearrangement conductors of transmission line, and distance from phase conductor and grounding system. The study recommended to keep safety distance operation in high voltage transmission lines with the necessity for engineer to take into account the effect of electromagnetic interference in the design stage of high voltage transmission power system, and to avoid any addition cost may be occur due to neglected effects of electromagnetic interference that produces by high voltage transmission lines

Analytical expression for estimation of the fault location in cable line

A new method for the fault location in a short cable line is proposed in this study. Based on the transmission line theory and circuit theorems, an analytical expression for estimating the fault location in the cable line is derived. According to the problem of incorrect estimation in the high-frequency band, the corresponding essential reason is comprehensively explained. By solving this problem, the fault location can be obtained accurately by the proposed method. To validate the proposed method, some experiments with a 50 Ω coaxial cable are implemented and the accuracy of the proposed method is tested. Meanwhile, it has been validated in these experiments that the proposed method is independent of the fault impedance and terminal impedances.

Cyclic voltammetry of porous carbon is impacted by charge redistribution – understanding the mechanism and effects on performance metrics

Ion-transport limitations in porous carbon can cause charge redistribution (CR) that significantly impacts cyclic voltammetry (CV) results and associated figures of merit. We elucidate these effects and the underlying mechanism using Vulcan XC 72 carbon and a Transmission Line Circuit (TLC). During the initial anodic scan, charge redistributes into the pores. The charged pores then act as a charge reservoir during the cathodic sweep and all subsequent CV cycles. Thus, pristine electrodes exhibit more positive currents than previously-cycled electrodes, causing higher anodic charge (capacity), capacitance and energy but lowering the cathodic charge, capacitance and energy, and the coulombic- and energy-efficiencies. When multiple sweep rates are run on the same electrode, there is a residual effect of the previous sweep rate; we show that applying sweep rates in order of decreasing magnitude must be avoided to eliminate significant bias in the data. Suggestions are made for designing CV protocols that minimize CR-based impacts on the CV profile and associated figures of merit. These considerations are vital to prevent erroneous conclusions due to CR and to allow comparisons between literature results. While this work focusses on carbon, the findings herein apply equally to other highly porous conductive materials and pseudocapacitive films.

Charging Dynamics of Overlapping Double Layers in a Cylindrical Nanopore.

The charging of electrical double layers inside a cylindrical pore has applications to supercapacitors, batteries, desalination and biosensors. The charging dynamics in the limit of thin double layers, i.e., when the double layer thickness is much smaller than the pore radius, is commonly described using an effective RC transmission line circuit. Here, we perform direct numerical simulations (DNS) of the Poisson-Nernst-Planck equations to study the double layer charging for the scenario of overlapping double layers, i.e., when the double layer thickness is comparable to the pore radius. We develop an analytical model that accurately predicts the results of DNS. Also, we construct a modified effective circuit for the overlapping double layer limit, and find that the modified circuit is identical to the RC transmission line but with different values and physical interpretation of the capacitive and resistive elements. In particular, the effective surface potential is reduced, the capacitor represents a volumetric current source, and the charging timescale is weakly dependent on the ratio of the pore radius and the double layer thickness.