Change In Current Distribution Research Articles

Research on numerical modeling of ac interference from high-speed railway to nearby buried pipeline

The large-scale construction of high-speed railways and buried pipelines has led to the parallel or intersection of these lines over long distances in some areas, resulting in dynamic AC interference to buried pipelines. In this paper, the modeling method of the AC interference from high-speed railway employing auto-transformer (AT) power supply mode to the buried pipeline was investigated, and the accuracy of the modeling method was verified by the simulation calculation of the actual field case and the comparison with the field data. Through modeling and calculation, the influence of train running position, rail to ground transition resistance and crossing angle on AC interference of high-speed railway is discussed. Based on the above research, it is analyzed that the dynamic AC interference is caused by the change of current distribution and the train load current. The main mechanism of AC interference caused by high-speed railway operation on nearby pipelines is inductive coupling. Especially when the rail to ground transition resistance is less than 50 Ω km, due to the unbalanced distribution of power supply circuit current, the peak AC interference voltage appears on pipeline where the train is located.

Evaluation of moth community changes and northward shifts in response to climate warming in Korea using both local and global occurrences

Although climate warming arguably induces changes in species distribution, thereby causing poleward shifts in various taxa, comprehensive research on the response of moths to climate warming is lacking. This study compared the distribution of macro-moths between historical (1978–2002) and recent (2011–2016) periods in South Korea using the macro-moth data collected at 18 survey sites to elucidate the changes in community composition. We used the community temperature index (CTI) to quantify the effect of temperature change on moth community changes. The CTI represents the average value of the species temperature index (STI; mid-value of thermal range) calculated using our local observations and global occurrences reported in the online database of the Global Biodiversity Information Facility. Our analysis revealed no significant difference in species richness between historical and recent surveys. However, some taxa, such as Uraniidae, Nolidae, Sphingidae, and Lasiocampidae, exhibited high turnover rates, while the number of sphingid moths with large body sizes greatly decreased. The temperature changes at the survey sites became pronounced with an increase in the survey interval (year) between historical and recent surveys (temperature increase = 0.0465 ℃ /year), while the CTI change exhibited a weak signal for northward shift of moth species. The CTI using the local data indicated 0.09 km/year of northward shift of moths, which is considerably slower than the northward shift (9.6 km/year) of the isothermal bands. However, the CTI using global occurrence data, expected to improve the estimation of species thermal niches, did not show any sign of northward shift. When observed, the northward shifts of moths were primarily identified in the cold-adapted species with low STI values, suggesting that cold-adapted species are more sensitive and vulnerable to climate warming than warm-adapted species. These results indicate that the current distribution changes of species were uneven, and the species adapted to cold regions are the ones primarily responding to the temperature increase by migrating northward and to high elevations.

Design and validation of frequency reconfigurable multiband antenna using varied current distribution method

Modern communication technologies require systems that can function at a wide range of frequencies, with diversity of radiation patterns, and with different types of polarization. In communication systems, the antenna serves as a filter; hence the ability to reconfigure the antenna is essential. The performance and design of a frequency band reconfigurable antenna are discussed in the paper, along with a comparison of the outputs of simulated and the fabricated design. Three PIN diodes are utilized to switch between various frequency bands. To increase selectivity, two ring resonators were added to the antenna's ground structure. As the current distribution changes in various switching instances, it is seen that the antenna operates at various resonant frequency bands. Connecting the diodes would change the current and field distribution in the chip design and thus change the resonant frequency. The antenna structure was designed and obtained results using High Frequency Simulation Structure (HFSS) software. The simulated and fabricated antenna is found to be operating in S band (2–4 GHz) and C (4–8 GHz) band of IEEE frequency bands with a gain in the range of 2.59 dB–9.54 dB. Typically the antenna resonates at various frequencies specifically, 2.38 GHz, 2.48 GHz, 3.98 GHz, 4 GHz, 4.45 GHz, 6.99 GHz, 7.2 GHz, 8.25 GHz. Under different switching cases of the diodes, the antenna is found to be radiating in different frequency ranges. By switching the PIN diodes under different cases, the current distribution path can be altered and as result of it, the antenna operates at variable frequencies.

Electromagnetic Forces Acting on Thin Flat Conductors of Pulse Power Equipment

The analysis of transverse electromagnetic forces acting on the edges of thin conductors during the flow of large impulse currents is carried out. Using the obtained analytical solutions and numerical modeling, the dependence of these forces on the current rise time to the maximum, configuration, and relative position of the conductors is demonstrated. The studies were carried out for single-wire and multiwire systems of flat conductors with current rise time variation within wide limits. It is shown that, when the current distribution changes from uniform to the corresponding ideal conductivity, the forces decrease by no more than two times. It is also shown that, in a number of cases in the system conductor-ideally conducting screens-there is no dependence of the transverse forces acting on the edges of the conductor on the frequency of the current.

Analysis about Change of the Armature's Average Speed for an Experimental Rail Launcher

In this paper, we measured the armature velocity of an experimental electromagnetic launcher by B‐dot method and analyzed the change of the armature's average speed. The electromagnetic gun launching process was also simulated by Ansoft Maxwell simulation software. The launch current is used as the model's excitation which means that the current in the model is the same as the rail current. Ansoft Maxwell's 3D model can accurately simulate the launching process, in theory. We found that there was an unexpected rise during the real launching process. The phenomenon can be discovered in the following several experiments. We analyzed several possible causes such as the inductive gradient change, rail broken and inaccurate measurement of B‐dot probe. The inductive gradient is an important parameter in the launching process and can affect the armature speed. After checking the measurement problem, we also found that the wave form of the output signal from the probe where the unexpected change occurred was normal but the amplitude was very small. The measurement method was proved correct. The rise of average inductance gradient leads to the unexpected increase in average speed and the small signal. Furthermore, the physical reason for the change of inductance gradient should be the change of current distribution. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Модель системы управления электрической плавильной печью с поддержанием сопротивления шлаковой ванны

The technique of modeling the control system of electric ore smelting furnaces with a closed arc and their investigation methods are considered. The study results made it possible to reveal qualitative and quantitative features and regularities of simultaneously occurring processes of energy distribution, heat and mass transfer, and localization of chemical and thermal processes in particular working space areas in which they are sharply nonlinear, with placing focus on the charge thermal conductivity and changes in current distribution between different working zone areas at high temperature gradients. It is shown that, as far as complex systems are concerned, the electrical and process modes of which are highly multifactorial and nonlinear in nature, whose parameters cannot be directly measured in full-scale measurements, it is advisable to use combined research methods that involve simulation models and full-scale experiments. For the cases when simulation models adequately reflect the real processes in an electric ore smelting furnace, the use of simulation models opens the possibility to obtain more reliable information about the values of the system parameters and their interactions, which is not available for field experiments. In particular, with regard to electric ore smelting furnaces with a closed arc, it is possible to divide the power released in the electric arc and in the crucible surrounding it. If their values are known, the production process can be conducted with better technical and economic indicators.

Effect of electrode-electrolyte spatial mismatch on transcranial direct current stimulation: a finite element modeling study

Objective. Despite the encouraging pilot results of transcranial direct current stimulation (tDCS) revealing its effectiveness in neuromodulation, there are also studies reporting inconsistent outcomes. Apart from previously studied factors, such as the differences in head model structures, anodal displacements, electrode shape and size, and connector position, the hypothesis that the inevitable spatial mismatch between the electrolyte buffer and electrode might shape current flow in the cerebral cortex was tested in this work, and our results potentially explain some of the reported inconsistent outcomes. Approach. A finite element head model was built using cylinder electrodes with an arbitrary diameter of 2 cm. Current flow induced by different spatial mismatch types, degrees, and directions was simulated for three montages targeting the left motor cortex. Voxel-level current density differences and Jaccard index values of different percentiles for each mismatched configuration were calculated and compared throughout the cerebral cortex to determine the effect of electrode-electrolyte geometric mismatch. Main results. Spatial mismatch between the electrolyte buffer and electrode affected the current density distribution in the cerebral cortex to different extents, depending on the position of the return electrode and mismatch type, degree, and direction. Single cortical voxel current-density variance induced by the 50% excess or insufficient mismatch was as high as 14.44% or 38.04%, respectively. Moreover, the distribution of variance changed directionally with the mismatch orientation. Compared with the insufficient mismatch and single-directional mismatch, the excessive and symmetrical mismatch caused a less obvious effect on the current density distribution of tDCS. Specifically, the symmetrical excess electrolyte caused around 2%–4% current density changes for all the montages, with different degrees and directions of mismatch. When the target position was fixed at C3, maximum sensitivity to the electrolyte-electrode mismatch was achieved with Iz as the return electrode, compared with the other two choices. Further, more than 20% voxels with >90% percentile of the peak current density values would shift position if >30% insufficient geometric mismatch occurred for montage C3-Iz. Significance. Our findings suggest that special attention is required regarding the spatial matching of the electrolyte buffer to the electrode during tDCS to avoid unexpected large changes in current distribution.

In-situ current distribution and mass transport analysis via strip cell architecture for a vanadium redox flow battery

Understanding mass transport mechanisms in VRFB electrodes is critical to improving performance, efficiency, and depth-of-discharge. In this study, diffusion and convection are experimentally investigated in a VRFB test bed using a strip cell architecture, having only one straight channel and 1 cm2 active area. To study diffusion and convection-dominated mass transport regimes, various channel depths (0.25, 0.5, 1, 2.5 mm) are employed. The diffusion-dominated condition is imposed with deeper channel depths while convection-dominated condition is achieved with shallower channel depths. It is found that diffusion-dominated cells have large current gradients; convection-dominated cells have relatively uniform current distribution from inlet to outlet under a mass transport limited condition. Although increasing flow rate is frequently found to improve electrochemical performance, it is observed that there is no discernible change in current distribution when increasing flow rate in diffusion-dominated VRFB cells. Pressure drop tests also show that superior electrochemical performance can be achieved with reduced relative pressure drop in convection-dominated cells. In light of such findings, an optimization point is proposed for the strip cell architecture; such a point will vary with any other architecture and system, but this approach can be applied to any flowing system.

Modification of spin-obit torques using the Ta oxidation buffer layer

Abstract We carefully investigated the influence of the thickness of TaOx buffer layer on the perpendicular magnetic anisotropy and spin-obit torques in Pt/Co/Pt trilayers. Using the first and second harmonic Hall voltage measurements, we found that both the perpendicular magnetic anisotropy field and the damping-like field are sensitive to the thickness of the TaOx layer. The damping-like torque with various TaOx thickness changes synchronously with the resistance of the device, which can be explained by the buffer TaOx layer induced current distribution changes in the bottom and top Pt layers. Through the current-induced magnetization switching measurement, we found that an optimal switching efficiency can be obtained by tuning the thickness of TaOx buffer layer.

Numerical Simulation and Cold Test of a Compact 2G HTS Power Cable

Superconductinge power cables offer the advantages of lower loss, lighter weight, and smaller dimensions, in comparison with conventional cables. It is important to developed most compact cable with a small diameter to increase the transmission power density of a cable. Precise analysis should be used to provide optimal cable layout with uniform current distribution among layers. We have developed an electric circuit model of a cable, and two FEM models using a finite-element code ANSYS. The numerical simulations can provide detailed information about the current distribution inside the cable and the optimal parameters from the point of view of current distribution of the cable have been determined. On the base of the models, the compact 2G HTS cable model with three layers in the core and two layers in the shield has been produced and tested. The outer diameter of the cable was as small as ~20 mm that is less than previously 1G and 2G HTS power cables tested. The experiment with the model cable demonstrated that even rather small mistake in the diameter of a layer leads to considerable change of current distribution among layers. This phenomenon was analyzed with the simulation models developed. It was shown that change of a layer diameter as small as the thickness of one tape (~0.1 mm) led to the current distribution change observed. Calculated results qualitatively coincide with the experiments. In addition, ac losses at different frequencies have been measured to compare them with ac loss in previously tested cables with larger diameter.

The analysis of dispersed generation influence on power system automatics settings and function algorithms

Dispersed generation (DG) objects are usually connected to distribution grid. This-type of grid supposes to have power system automatics (PSA) that comprise emergency control system (ECS). ECS serves for normal power supply scheme recovery after fault elimination, fault development prevention and system parameters maintenance in acceptable limits within fault and post-fault conditions. Generating power connection to the grid causes significant power flow and current distribution change. This might become a reason of ECS automatics misoperation. This paper presents the results of DG objects influence analysis on PSA settings and function algorithms. Implemented analysis has allowed to define post-fault conditions envelopes that have to be analysed within DG objects grid connection design and provide the recommendations for PSA settings and function algorithms change.

Dual-band reflectarray with crossed-dipole elements for GSM and LTE applications

A novel dual-band reflectarray for beam control of reflected waves at GSM and LTE bands is proposed in this paper. The reflectarray is constructed with two substrates separated at a distance form. Consisting of square ring and four stubs, the FSS cell element has the dual-band property for the changes of current distribution. A crossed-dipole element is printed on the surface of another substrate, and the progressive phase distribution is achieved for the reflected wave by adjusting the resonant length of the crossed-dipole element. The reflectarray can independently control the direction of both horizontally and vertically polarized reflect beams at two resonant frequencies. A reflectarray comprising 7 by 5 elements with operation at 1.7GHz and 2.7GHz is studied and measured, which can be applied in the GSM and LTE communication systems.

Impact of Hot Carrier Aging on Random Telegraph Noise and Within a Device Fluctuation

For nanometer MOSFETs, charging and discharging a single trap induces random telegraph noise (RTN). When there are more than a few traps, RTN signal becomes complex and appears as within a device fluctuation (WDF). RTN/WDF causes jitters in switch timing and is a major challenge to low power circuits. In addition to RTN/WDF, devices also age. The interaction between RTN/WDF and aging is of importance and not fully understood. Some researchers reported aging increasing RTN/WDF, while others showed RTN/WDF being hardly affected by aging. The objective of this paper is to investigate the impact of hot carrier aging (HCA) on the RTN/WDF of nMOSFETs. For devices of average RTN/WDF, it is found that the effect of HCA is generally modest. For devices of abnormally high RTN/WDF, however, for the first time, we report HCA reducing RTN/WDF substantially (>50%). This reduction originates from either a change of current distribution or defect losses.

Effect of wall thickness and helium cooling channels on duct magnetohydrodynamic flows

The concept of dual coolant liquid metal (LM) blanket has been proposed in different countries to demonstrate the technical feasibility of DEMO reactor. In the system, helium gas and PbLi eutectic, separated by structure grid, are used to cool main structure materials and to be self-cooled, respectively. The non-uniform wall thickness of structure materials gives rise to wall non-homogeneous conductance ratio. It will lead to electric current distribution changes, resulting in significant changes in the velocity distribution and pressure drop of magnetohydrodynamic (MHD) flows. In order to investigate the effect of helium channels on MHD flows, different methods of numerical simulations cases are carried out including the cases of different wall thicknesses, single pass of helium cooling channels, and three types of dual helium cooling channels. The results showed that helium tubes are able to affect the velocity distribution in the boundary layer by forming wave sharp which transfers from Hartmann boundary layer to the core area. In addition, the potential profile and pressure drop in the cases have been compared to these in the case of walls without cooling channel, and the pressure gradient of a simplified single short duct MHD flow in blanket shows small waver along the central axis in the helium channel position.

Study of acetylene poisoning of Pt cathode on proton exchange membrane fuel cell spatial performance using a segmented cell system

Acetylene is a welding fuel and precursor for organic synthesis, which requires considering it to be a possible air pollutant. In this work, the spatial performance of a proton exchange membrane fuel cell exposed to 300 ppm C2H2 and different operating currents was studied with a segmented cell system. The injection of C2H2 resulted in a cell performance decrease and redistribution of segments' currents depending on the operating conditions. Performance loss was 20–50 mV at 0.1–0.2 A cm−2 and was accompanied by a rapid redistribution of localized currents. Acetylene exposure at 0.4–1.0 A cm−2 led to a sharp voltage decrease to 0.07–0.13 V and significant changes in current distribution during a transition period, when the cell reached a voltage of 0.55–0.6 V. A recovery of the cell voltage was observed after stopping the C2H2 injection. Spatial electrochemical impedance spectroscopy (EIS) data showed different segments' behavior at low and high currents. It was assumed that acetylene oxidation occurs at high cell voltage, while it reduces at low cell potential. A detailed analysis of the current density distribution, its correlation with EIS data and possible C2H2 oxidation/reduction mechanisms are presented and discussed.

J0560204 磁気センサを用いた固体高分子形燃料電池における内部診断方法の検討

The current distribution is an evaluation index of PEFC because non-uniform current distribution leads to low utilization of reactants and catalysts. Additionally, current distribution is affected by the reactant flow arrangement and operation conditions. Therefore, it is important to measure and evaluate the current distribution of PEFCs. Many methods to measure current distribution exist, but most modify components of the PEFC. For instance, a method may segment the flow field and measure current distribution using the printed circuit board and resistors network. In order to measure the current distribution of PEFC systems, which are typically stacked, the methods must be non-destructive. In order to realize a non-destructive current distribution measurement approach for use in PEFC stacks, we use some magnetic sensor probes. Here, we described the measurement system and the method using these proves. And current distribution in PEFC was evaluated in its operating condition. The study showed that the current distribution changes by air flow rates and relates the performance of PEFC.

Modeling Effects of Scar on Patterns of Dorsal Column Stimulation

The purpose of this study was to examine how scar formation may affect electrical current distribution in the spinal cord when using paddle leads placed in the epidural space during treatment with spinal cord stimulation. A finite element model of the spinal cord was used to examine changes in stimulation using a guarded cathode configuration with and without scar. Additionally, two potential "compensatory" programming patterns were examined in order to understand how the three-dimensional electrical field may be affected by scar. Direct comparisons with prior studies in the literature and use of known anatomy of dorsal column fiber distributions also enabled a computational estimate of the number of fibers likely reaching threshold with each stimulus pattern. Notable potential and current distribution changes were found related to the modeled scar. Compensatory stimulation patterns (both in spatial and in amplitude dimensions) affect the fiber activation patterns in complex ways that may not be easily predetermined by a programming specialist. This study is one of the first to examine the effects of scar tissue on dorsal column stimulation and the only one using a detailed computational approach toward that end. It appears that different thickness and location of scar between electrode contacts and the dura may likely lead to a significant number and location of complex changes in the activated fibers. It is likely that a more complete assessment of scarring and its effect on the electrical environment of any given paddle lead would allow more accurate and predictable reprogramming of patients with commercially available systems in place.

Magnetic field inverse problem of grounding grid and its application

When the current distribution changes due to the breakage in the grounding grid, the magnetic field in the vicinity of the grounding grid will change, hence the magnetic field on the ground above the grounding can be used to detect the breakage of the grounding. In the paper, the magnetic field forward problem of the grounding grid is described firstly, and simulations were carried out when the breakage was located at different position. Results indicate that the maximum change of the magnetic flux density occurs at different measuring point when the breakage was located at different position. To achieve a more convenient method to detect the grounding grid fault, the magnetic field inverse problem of the grounding grid is presented, which is the process to calculate the current flowing in the grounding grid according to the magnetic field strength, and the method based on the global regularization and Damped Gauss-Newton method to solve the inverse problem is described, with which the ill-posed and ill-conditioning characteristic of the inverse problem can be diminished. Then the fault state of the grounding grid can be confirmed in the following way. Firstly, inject a 10∼30A current into the grounding grid, measure the magnetic field strength or the magnetic flux density at the measuring points on the ground above the grounding grid, then the current distribution can be obtained by solving the inverse problem. If the parameters of the soil are known, the resistance distribution can be obtained, with which the fault state of the grounding grid and the location of the fault can be confirmed. An equivalent model to verify the inverse problem was set up, and results indicate that the global regularization can diminish the ill-posed and ill-conditioning characteristic of the inverse problem.

ANALYSIS OF ELECTROMAGNETIC FIELD AND JOULE HEATING OF ELECTROSLAG REMELTING PROCESSES

A 3D finite element model was developed to simulate the magnetic field, electromag- netic force, current density and Joule heating of electroslag remelting processes (electrode, slag and ingot) by using of Maxwell equation, Lorentz law and Joule law. Especially, the skin effect is shown and discussed based on numerical results. The results show that the current distribute on the external surfaces of slag and ingot. In slag, due to the low electrical conductivity of slag, the current distribution changes, gathering on the end of electrode. The maximum electromagnetic force is at the upper surface nearby the electrode and the maximum joule heating is at the interface of electrode and slag. When current frequency is greater than 35 Hz, the vortex flow will occur in interior of electrode and ingot. When electrode immersion depth increase and slag cap thickness decrease, the maximum of the joule heat in slag will increase.

Conductive atomic force microscopy studies on the transformation of GeSi quantum dots toquantum rings

Conductive atomic force microscopy has been employed to study the topography andconductance distribution of individual GeSi quantum dots (QDs) and quantum rings (QRs)during the transformation from QDs to QRs by depositing an Si capping layer on QDs. Thecurrent distribution changes significantly with the topographic transformation during the Sicapping process. Without the capping layer, the QDs are dome-shaped and theconductance is higher at the ring region between the center and boundary than that at thecenter. After capping with 0.32 nm Si, the shape of the QDs changes to pyramidal and thecurrent is higher at both the center and the arris. When the Si capping layerincreases to 2 nm, QRs are formed and the current of individual QRs is higher at therim than that at the central hole. By comparing the composition distributionsobtained by scanning Auger microscopy and atomic force microscopy combined withselective chemical etching, the origin of the current distribution change is discussed.