Transient Circuit Research Articles

A novel transient thermal circuit model of buried power cables for emergency and dynamic load

In order to improve the utilization rate of cable while ensuring safety and reliability, accurate and rapid evaluation of transient temperature rise of directly buried power cables is useful to improve the management level of dynamic capacity increase and emergency load conditions. Since the existing thermal circuit model is relatively complex or not very accurate, an equivalent three-branch transient thermal circuit model is presented for the complex cable structure and heat dissipation environment based on the uniqueness of the temperature field. Considering the electric circuit similarity, the transient analysis method of the centralized parameter network in the circuit is used to establish the transient adjoint model of the thermal capacity branch, provide the node conduction matrix of the transient thermal circuit model, and write the node temperature rise equation as a function of the node heat flow. By comparing the solution of the thermal circuit model with the finite element results, and the genetic algorithm is used to optimize and obtain the equivalent thermal resistance and thermal capacity parameters of the transient thermal circuit model. The comparison of finite element calculation results proves that the proposed three-branch transient thermal circuit model is more accurate than the two-branch thermal circuit model. Compared to the traditional all-part thermal circuit model, the three-branch model can be rapidly solved and easily applied in engineering.

Electrochemical co-deposition of cobalt and graphene, produced from recycled polypropylene, on TiO2 nanotube as a new catalyst for photoelectrochemical water splitting

In this study, to improve the photoelectrochemical properties of TiO2 nanotubes (TNT), the hybrid TNT-graphene-Co(OH)2 was prepared using electrodeposition of graphene and cobalt salt. The employed graphene was obtained from the waste polypropylene using chemical vapor deposition method. The hybrid material showed high thermal stability and promising visible light absorption. Moreover, its XRD pattern and Raman spectrum are in accordance with the precursors. The photoelectrochemical performance of this hybrid material was investigated using linear sweep voltammetry, transient open circuit potential, and chronoamperometry. Because of the existence of graphene, the prepared hybrid material exhibited excellent photoelectrochemical properties and the results were more appropriate than those of TNT and cobalt deposited TNT. Among the various samples with different amounts of graphene, the sample with the highest graphene content showed the highest photoelectrochemical abilities. This improvement is mainly related to the visible-light harvesting ability of graphene and facile recombination of photogenerated electron-hole pairs due to the synergistic effect of the involved materials.

Thickness dependent wavelength selective NIR-UV-visible photoresponse in ZnO nanowires and silicon heterojunction

In this paper, we report ZnO nanowires (NWs) and silicon-based type-II PN heterojunction for UV–Visible–Infrared self-powered photodetection. The as-grown ZnO NWs were highly crystalline and aligned along the c-axis in the [002] direction revealed in the HRTEM and XRD measurements. The Hall measurements revealed the n-type behavior for ZnO and p-type for p-Si with carrier concentrations of 4.09 × 1016 cm−3 and 1.38 × 1017 cm−3, respectively. The depletion widths were estimated to be ∼35 nm and ∼120 nm, respectively for p-Si and n-ZnO NWs. The Ag/n-ZnO NWs/p-Si/Ag PN heterojunction showed large photoresponse, even at zero bias, under the illumination of commercially available UV–Visible–NIR LEDs, thus acting as a self-powered photodetector. It was interesting to observe that the photoresponse was dependent on the growth time and hence the thickness of ZnO NWs thin film. A maximum zero bias responsivity of ∼0.1 A/W at green (515 nm) was observed and was large for the junction with thicker ZnO NWs film (5 h growth), compared with thinner (3 h growth) device under IR (950 nm) LED illumination, however, it was observed otherwise for UV (395 nm) LED. This suggests that tuning the thickness of the ZnO NWs thin film results in the wavelength selective photoresponse, consequently, paving the way towards UV blind IR-visible photodetector based on ZnO NWs. The transient short circuit current (Isc vs t) and open circuit voltage (Voc vs t) properties showed fast and large responses under periodic illumination of all LEDs (UV–Vis–NIR). The response was observed to depend on the intensity of light and the maximum Voc comes out to be ∼102 mV and Isc ∼5.58 μA, under the illumination of a red laser diode.

A Fast Transient Low-Dropout Regulator with High-Power Supply Rejection

With the continuous popularization of portable electronic products in electronic information, aerospace, biomedicine and other fields, low-dropout regulator (LDO) has become an important part of modern power management chips. Compared with other power management modules, it has the advantages of low power consumption, high power supply rejection, and strong anti-noise capability. However, the LDO power tube has a large width-to-length ratio, so when the load changes transiently, the gate of the power tube cannot respond in time, resulting in an overshoot and undershoot of the output voltage and a long recovery time. In this paper, the LDO transient enhancement circuit is designed. When the load changes transiently, the power tube gate capacitor is quickly charged and discharged, which overcomes the overshoot voltage and undershoot voltage. While improving the transient response of traditional LDO, the structure ensures the power supply rejection (PSR) and other performance of the circuit. According to the results, with an input of 2.5 V, the output voltage is regulated to 1.2 V, and PSR is -80 dB. When the load changes by 20 mA in 1 μs, it is stable within 1.2 μs while the undershoot voltage is controlled at 51 mV and the overshoot voltage is controlled at 65 mV.

Orbitofrontal cortex populations are differentially recruited to support actions

The ability to use information from one's prior actions is necessary for decision-making. While orbitofrontal cortex (OFC) has been hypothesized as key for inferences made using cue and value-related information, whether OFC populations contribute to the use of information from volitional actions to guide behavior is not clear. Here, we used a self-paced lever-press hold-down task in which mice infer prior lever-press durations to guide subsequent action performance. We show that the activity of genetically identified lateral OFC (lOFC) subpopulations differentially instantiate current and prior action information during ongoing action execution. Transient state-dependent lOFC circuit disruptions of specified subpopulations reduced the encoding of ongoing press durations but did not disrupt the use of prior action information to guide future action performance. In contrast, a chronic functional loss of lOFC circuit activity resulted in increased reliance on recently executed lever-press durations and impaired contingency reversal, suggesting the recruitment of compensatory mechanisms that resulted in repetitive action control. Our results identify a novel role for lOFC in the integration of action information to guide adaptive behavior.

Transient Linear Circuit Analysis Using Finite Element Technique

In this paper, a novel algorithm for a transient linear circuit analysis based on the Finite Element Technique (FET) was established. The FET procedure allows a straightforward solution for complex electric circuits since it is based on the Finite Element Method (FEM) approach. The developed algorithm allows us to select various types of time integration schemes when forming a local system of equations for a coupled circuit finite element. To illustrate the basic principle of the developed FET-based algorithm and to perform transient analysis, a random coupled linear circuit was analyzed. Numerical solutions obtained using Heun’s and the generalized trapezoidal rule (ϑ-method) integration schemes were compared to the solution obtained by Matlab Simulink software. It was shown that the accuracy of results depends on the employed time integration scheme when performing the FET procedure. It was shown that using Heun’s method as the time integration scheme yields more accurate results than using the ϑ-method time integration scheme.

Straightforward Modeling of Frequency Dispersive and Nonlinear Common Mode Chokes for Transient Simulations

The simulation and design process of electromagnetic compatibility (EMC) filters need accurate models for their used components. Common mode chokes, which are essential filter components, exhibit a complex behavior that is usually hard to model for the purpose of transient circuit simulation. This article gives an easy method of modeling such components as long as hysteretic effects can be neglected. The process presented produces an easy to setup and easy to use SPICE model. The incorporated effects are the frequency dependent impedance behavior as well as the nonlinear effect from saturation processes. Both effects are well separated in the model and require only data from the manufacturer, thereby circumventing data fitting methods and measurements on samples with their lead and shipping time efforts. The frequency dependent behavior is modeled via a discrete <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RL</i> -ladder model whereas the nonlinear effects are integrated via treating the saturation as a phase transition. The choke modeling technique was verified for a typical current pulse shape. The comparison between the measurement and the simulation model showed a good match, especially for the maximum amplitude of the current pulse shape, which is essential to determine saturation.

Finite Element Extraction of Frequency-Dependent Parasitics

We propose a stable and efficient approach to extract the frequency-dependent parasitic effects of any computer-aided design (CAD) model with the finite element method (FEM). An equivalent circuit (EC) of the parasitics for use in transient circuit simulations is generated by applying vector fitting to the result of a full-wave simulation on the one hand and to a magnetoquasistatic (MQS) simulation result on the other hand. The circuit generated from the magnetoquasistatic results is combined with capacitances computed in an electrostatic (ES) simulation. This separate consideration of resistive and inductive, and capacitive effects ensures stability also at low frequencies by avoiding impedance or scattering matrices that otherwise would become ill-conditioned when approaching the dc point. A comparison of measurement and simulation results for the example of a common mode (CM) choke validates the method.

Conversion Matrix Method of Moments for Time-Varying Electromagnetic Analysis

A conversion matrix approach to solving network problems involving time-varying circuit components is applied to the method of moments for electromagnetic scattering analysis. Detailed formulations of this technique's application to the scattering analysis of structures loaded with time-varying circuit networks or constructed from general time-varying media are presented. The computational cost of the method is discussed, along with an analysis of compression techniques capable of significantly reducing computational cost for partially loaded systems. Several numerical examples demonstrate the capabilities of the technique along with its validation against conventional methods of modeling time-varying electromagnetic systems, such as finite difference time domain and transient circuit co-simulation.

High‐Performance n‐Channel Printed Transistors on Biodegradable Substrate for Transient Electronics

AbstractInnovative methods to fabricate and integrate biodegradable high‐grade electronics on green substrates are needed for the next generation of robust high‐performance transient electronics. This is also needed to alleviate the growing problem of electronic waste (e‐waste). Herein, the authors present the n‐channel silicon (Si) nanoribbons‐based high‐performance transistors developed on biodegradable metal (magnesium) foils using the direct transfer printing method. The developed transistors present high effective mobility of &gt;600 cm2 V−1 s−1, high on/off current ratio (Ion/off) of &gt;104, negligible hysteresis, transconductance of 0.19 mS, and an on‐current of 1.6 mA at a bias of 2 V. Further, the transistors show stable device performance under temperature stress (5–50 °C), gate‐bias stress, continuous long‐term transfer scans for 24 h (&gt;3000 cycles), and aging test (up to 100 days) demonstrating the excellent potential for futuristic high‐performance robust transient devices and circuits. Finally, the effect of transience on the electrical functioning of devices on Mg foils (at pH 8) and degradation of Mg foils at different pH values is studied by hydrolysis. The outcome from these experiments demonstrates the potential of direct transfer printing for high‐performance transient electronics and also as the new avenue toward zero e‐waste.

Transient Out‐of‐Equilibrium Nucleic Acid‐Based Dissipative Networks and Their Applications

AbstractDynamic, dissipative reactions play important roles in biological processes, and emulating such biological processes by artificial circuits and networks is a challenging topic in the area of Systems Chemistry. The present article summarizes efforts to apply the information encoded in the base sequence of nucleic acids to assemble transient, dissipative DNA‐based networks mimicking natural processes. The design principles of the transient nucleic acid‐based systems are introduced. Triggered reaction moduli lead to a transient intermediary constituent recovered to the parent moduli by enzymes, DNAzyme, or light as control units are described. Transient DNA‐based circuitries of enhanced complexities revealing temporal gated or cascaded transformations are demonstrated. Different applications of dynamically triggered transient circuits are introduced, including the temporal aggregation and deaggregation of plasmonic nanoparticles or semiconductor quantum dots and the control over their optical properties, the transient release and uptake of loads by aptamer scaffolds, and the transient reconfiguration of constitutional dynamic networks and the control over emergent catalytic functions. The future perspectives of dissipative nucleic acid‐based networks and their potential future applications are discussed.

Research on EMI of Traction Network Transient Current Pulse on Shielded Cable Terminal Load

The transient current pulse (TCP) caused by the traction network short-circuit fault (TNSF) will produce a high-strength transient electromagnetic field (TEMF). The electromagnetic field will interfere with nearby weak current equipment through the shielded cable. In this paper, a transient circuit model (TCM) for the short-circuit traction network is proposed to calculate the transient current. The short circuit is equivalent to a ring, and the TEMF transient electromagnetic field is calculated based on the magnetic dipole. The current response of the TEMF transient electromagnetic field on the shielded cable is deduced based on the transmission line theory and verified by experiments. The electromagnetic interference (EMI) of a TEMF transient electromagnetic field to the shielded cable terminal load were was studied under various incidence angles, azimuth angles, and polarization angles. The results demonstrate that the greater the incident angle and azimuth angle, the greater the EMI on the terminal load. The horizontal distance between the shielded cable head and the short-circuit point should be greater than 6 m, and the incident angle should be greater than 45∘. This method can provide a theoretical basis for the electromagnetic compatibility research of traction power supply systems and their nearby weak current equipment.

Damping analysis of power system stabilizer based on transient equivalent circuit

Damping analysis of power system stabilizer based on transient equivalent circuit

An Ultra-low Power Off Chip Capacitor-less LDO With High Transient Response

This paper presents a low-dropout linear regulator (LDO) with ultra-low power high transient response. This LDO adopts GAP-dynamic-bias circuit to achieve quiescent current as low as 242nA under 0-20mA load. A transient enhancement circuit based on window comparator is used to sense the output voltage change and further enhance the transient response. The circuit is designed and implemented using TSMC0.18um technology, and is verified by simulation using Spectre software. The simulation results show that when the load changes in the range of 10uA-20mA with a 1ns transition edge, the slowest overshoot and undershoot recovery times are only 2.36us and 2.15us. In the input voltage range of 2.5-3.6V, the linear regulation rate and load regulation rate are 0.479mV/V and 2.61nv/mA, respectively.

Differential heat-flow-type warmth sensor for object material discrimination with reduced sensor output error due to object temperature

This paper presents a differential heat-flow-type warmth sensor for highly accurate material discrimination by robots. In the previous study, we demonstrated a warmth sensor that identifies the material of a contacted object by its heat-flow-peak value. However, the previous heat-flow-type warmth sensor had a sensor output error in which the heat-flow-peak value changed depending on the temperature of the contacted object. In the present effort, to reduce the sensor output error, we propose a differential-type sensor composed of the two warmth sensors, based on the thermal equivalent circuit. First, the transient thermal equivalent circuit model was simulated to confirm the principle that it cancels the sensor output error. Then, a differential heat-flow-type warmth sensor with dimensions of 10.0 × 24.0 × 5.0 mm3 was fabricated by integrating two warmth sensors with thermal insulators. Finally, experimental results successfully demonstrated that the sensor output error can be reduced to − 0.17 mW/°C or less, which is almost 1/16 the error of the previous sensor.

Neurophysiology of the Developing Cerebral Cortex: What We Have Learned and What We Need to Know.

This review article aims to give a brief summary on the novel technologies, the challenges, our current understanding, and the open questions in the field of the neurophysiology of the developing cerebral cortex in rodents. In the past, in vitro electrophysiological and calcium imaging studies on single neurons provided important insights into the function of cellular and subcellular mechanism during early postnatal development. In the past decade, neuronal activity in large cortical networks was recorded in pre- and neonatal rodents in vivo by the use of novel high-density multi-electrode arrays and genetically encoded calcium indicators. These studies demonstrated a surprisingly rich repertoire of spontaneous cortical and subcortical activity patterns, which are currently not completely understood in their functional roles in early development and their impact on cortical maturation. Technological progress in targeted genetic manipulations, optogenetics, and chemogenetics now allow the experimental manipulation of specific neuronal cell types to elucidate the function of early (transient) cortical circuits and their role in the generation of spontaneous and sensory evoked cortical activity patterns. Large-scale interactions between different cortical areas and subcortical regions, characterization of developmental shifts from synchronized to desynchronized activity patterns, identification of transient circuits and hub neurons, role of electrical activity in the control of glial cell differentiation and function are future key tasks to gain further insights into the neurophysiology of the developing cerebral cortex.

Decoration of g-C3N4 by inorganic cluster of polyoxometalate through organic linker strategy for enhancing photoelectrocatalytic performance under visible light

The efficient visible light-driven photoelectrocatalyst (denoted as g-C3N4-CO-TETA-Pr-SiW11) was designed through the organic linker strategy by combination of polyoxometalate (POM) (cluster of [SiW11O39]−8 (SiW11)) with graphitic carbon nitride (g-C3N4). For this purpose, a reactive tetradentate NH2 linker was introduced by oxidation and subsequently amidation reactions on the surface of g-C3N4 frameworks then SiW11 was bonded to the organic linker to generate g-C3N4-CO-TETA-Pr-SiW11. In this study, for the first time, this organic linker strategy was applied for covalent combination of POM and g-C3N4 to design a stable photocatalyst with high-performance. Photoelectrocatalytic performance of prepared catalysts was investigated under visible light irradiation. The photocurrent density of 0.17 mA cm−2 for g-C3N4-CO-TETA-Pr-SiW11 compared with 0.077 mA cm−2 for g-C3N4 was achieved. Investigation of the transient open circuit potential decay and photoluminescence showed the efficient electron-hole separation for g-C3N4-CO-TETA-Pr-SiW11. The arc diameter in Nyquist plots indicated the improved charge transfer and charge carrier's lifetimes after decorating of g-C3N4 with POM. Mott−Schottky plots demonstrated a greater electron transfer at the photo electrode/electrolyte interface for g-C3N4-CO-TETA-Pr-SiW112.8 in compared to g-C3N4. Also, the photoconversion efficiency exhibited more than 2.4 time enhancement for g-C3N4-CO-TETA-Pr-SiW11 photoanode compared to g-C3N4.

Detection and Prediction of Internal-Caused Fire in Tunnel Cable by an Equivalent Transient Thermal Circuit Model

Internal-caused cable fires are one of the most common cable fires, and anomalous temperature increase of the cable core is one of the first signs. However, when a cable is operating with electricity, the temperature of the core conductor cannot be monitored directly; therefore, this characteristic cannot be used in detection and prediction of internal-caused fire in electric cable effectively. An analogous transient thermal circuit model is created, simplified, and optimized to properly compute the temperature of the cable core. Afterward, by using the cable internal-caused fire experimental platform and adjusting current carrying capacity of the tested cable, an experiment is conducted for stimulating the very early stage of three-core cable internal-caused fire. The maximum relative errors of the transient thermal circuit model and the trisection transient thermal circuit model are less than 10% when comparing the experimental data with the calculation results, and the average relative error of the calculated value of trisection transient thermal circuit model is 1.08% after layered optimization. The algorithm model can satisfy the requirement for early detection and prediction in the very early stage of cable internal-caused fire.

Inclusion of frequency dependences into prediction model of conducted electromagnetic emissions for a VFD motor system

This paper presents a quantitative prediction model of conducted electromagnetic emissions (EME) for a variable frequency drive (VFD) motor system based on the macro-modeling approach. This model relies on the effective representations of the frequency dependent characteristics of the parasitic behaviors between converter arms and heatsink, of shielded power cable, and of motor windings. The frequency dependent performances between converter arms and heatsink, and of the motor windings are obtained by processing measurement data. Then the vector fitting method (VFM) with passivity enforcement and circuit synthesis method are adopted to obtain the corresponding equivalent circuits. The equivalent circuit implementation of shielded power cable is achieved by applying a node-to-node admittance functions (NAFs) model, which considers the propagation phenomenon and frequency dependent losses accurately. The conducted EME model is compatible with commonly used transient circuit solvers since it only includes constant circuit elements. The conducted emissions of the VFD system are then evaluated by analyzing the common mode (CM) and differential mode (DM) voltages and currents.

Voltage Stability Analysis of Large Scale PV Plant Reactive Power Control Methods

The increasing integration of photovoltaic (PV) plants in conventional power systems has led to the need to examine the effects of these plants on the system dynamics. In this study, a well-known IEEE-9 bus power system is modified by integrating PV plant in DigSilent Powerfactory environment. Then, 3 transient cases are tested by using PV plant control units designed by Western Electricity Coordinating Council (WECC). The effect of load and line transient disconnections and 3-phase short circuit fault on modified power system are investigated as case-I, case-II, and case-III, respectively. In all cases, two sub-cases are considered according to the location. As a result, comparison of PV system reactive power control methods (RPCM) is analyzed in terms of voltage stability in these 3 cases.