Conductor Model Research Articles

基于最速降线的T型槽开沟装置导种管设计与试验

The disorder flow of seeds caused by the collision in the seed-guiding tube is one of the important reasons for the reduction of seeding uniformity. For this problem, a seed-guiding tube with brachistochrone considering the influence of friction was presented in this paper. By analyzing kinetics and rotating the equation coordinate system, brachistochrone under the condition of friction was obtained and applied to the design of the structural parameters of the grain conductor of T-groove furrowing device, and a discrete element model of the grain conductor and wheat was established, thus single-factor simulation analysis and quadratic regression orthogonal rotation combination simulation tests were conducted to explore the optimal combination of parameters. The test results showed that the seed-guiding tube had a brachistochrone radius of 14.708 mm, a linear length of 500 mm and a working speed of 4 km/h, and the seed spacing offset dispersion degree and the seed lateral offset dispersion degree were 12.26 and 8.53 respectively, which had a high seeding uniformity. The results of the bench validation test showed that the coefficients of variation of the two test evaluation indexes between the bench test results and the virtual simulation results were 10.20% and 8.62% respectively, therefore the simulation results could be used for the optimization of the seed guide tube.

Brain signal predictions from multi-scale networks using a linearized framework.

Simulations of neural activity at different levels of detail are ubiquitous in modern neurosciences, aiding the interpretation of experimental data and underlying neural mechanisms at the level of cells and circuits. Extracellular measurements of brain signals reflecting transmembrane currents throughout the neural tissue remain commonplace. The lower frequencies (≲ 300Hz) of measured signals generally stem from synaptic activity driven by recurrent interactions among neural populations and computational models should also incorporate accurate predictions of such signals. Due to limited computational resources, large-scale neuronal network models (≳ 106 neurons or so) often require reducing the level of biophysical detail and account mainly for times of action potentials (‘spikes’) or spike rates. Corresponding extracellular signal predictions have thus poorly accounted for their biophysical origin.Here we propose a computational framework for predicting spatiotemporal filter kernels for such extracellular signals stemming from synaptic activity, accounting for the biophysics of neurons, populations, and recurrent connections. Signals are obtained by convolving population spike rates by appropriate kernels for each connection pathway and summing the contributions. Our main results are that kernels derived via linearized synapse and membrane dynamics, distributions of cells, conduction delay, and volume conductor model allow for accurately capturing the spatiotemporal dynamics of ground truth extracellular signals from conductance-based multicompartment neuron networks. One particular observation is that changes in the effective membrane time constants caused by persistent synapse activation must be accounted for.The work also constitutes a major advance in computational efficiency of accurate, biophysics-based signal predictions from large-scale spike and rate-based neuron network models drastically reducing signal prediction times compared to biophysically detailed network models. This work also provides insight into how experimentally recorded low-frequency extracellular signals of neuronal activity may be approximately linearly dependent on spiking activity. A new software tool LFPykernels serves as a reference implementation of the framework.

Electromagnetic Modeling of Lossy Interconnects From DC to High Frequencies With a Potential-Based Boundary Element Formulation

The accurate electromagnetic modeling of both low- and high-frequency physics is crucial in the signal and power integrity analysis of electrical interconnects. The boundary element method (BEM) is appealing for lossy conductor modeling because it can capture the frequency-dependent variation of skin depth with only a surface-based discretization of the structure. Conventional BEM formulations rely on the mutual coupling of electric and magnetic fields, and can become inaccurate or unstable at low frequencies. We develop a new full-wave BEM formulation based on potentials which can accurately model lossy conductors from exactly DC to very high frequencies. A new set of simple boundary conditions is proposed along with a modified Lorenz gauge to ensure that the proposed formulation has a stable condition number down to DC. Moreover, coupling the potential-based integral equations to a circuit model allows the straightforward extraction of network parameters. Realistic numerical examples at both the chip and package level demonstrate the accuracy and stability of the proposed method from DC to high frequencies, beyond the capabilities of state-of-the-art BEM formulations based on fields.

Integrated Inductor Model Verification for Microwave LC-filters in Si and SiGe Systems on a Chip

In this paper, the conductor model that can be used to design of various inductor layout configurations for any Si and SiGe technological processes is considered. The experimental prototypes of the test inductors were produced in the standard SiGe BiCMOS 130 nm process to verify the model. The chips measuring results showed that the characteristics of the prototypes taking into account the manufacturing tolerance are in the range of model simulated values. It has been found that the proposed model has a better convergence with the prototypes characteristics than 3D modeling. The equivalent circuit simulation speed can be orders of magnitude higher than the 3D simulation speed. The proposed model accuracy is achieved by taking into account the skin-effect and edge-effects in the dielectric and substrate. Using the skin-effect equivalent circuit the model can be run in Cadence Specter Simulator. It is necessary for the microwave LC-filters development.

A method for automated modeling of plasma shape control response in tokamaks

A simple method commonly used in modeling of tokamak conductor and plasma response for plasma control has been extended to allow more general modeling of tokamak PF conductor circuits. This extension combines a previously existing method for integrating plasma response and tokamak circuits with a more capable circuit modeling technique derived from the theory that underlies present-day automatic circuit simulation codes. This combined method can incorporate any combination of inductors (e.g., coils), resistors, capacitors, voltage sources, and current sources, while retaining the same model structure and ease of interpretation as the simple method. For many tokamaks, use of this extended method would not be the preferred approach, but for certain devices or for specialized models of a device, it is useful and occasionally essential. For example, the method has enabled fast and automated modeling of the complicated and daily-changing circuit topology used in the DIII-D tokamak. This automated modeling is essential to the support of controller design for the frequently changing requirements for DIII-D plasmas. It is likely to also find application in the workflows for new device designs.

Hybrid Method for Numerical Implementation of Segmented Power Cable Conductors in Finite-element Based Ampacity Calculation

This paper addresses challenges with modelling of segmented power cable conductors using finite element analysis (FEA) for ampacity calculation. Segmented conductors improve current distribution by minimizing skin and proximity effects, thus reducing conductor losses. 2D FEA simulation offers high flexibility and accuracy beyond IEC 60287 for complex laying geometries, but the modelling of losses in segmented constructions using FEA has proven difficult due to the big difference in wire size and twisting pitch, requiring great amounts of computational power. In this paper a hybrid method is proposed, in which the IEC 60287 empirical formulae for segmented conductors are included in a 2D FEA model. The proposed method shows a good correspondence to IEC standard calculations, with deviations in conductor AC resistance of less than 1 %.

Analytical Delay Model and Stability Analysis for MLGNR Interconnects

This paper analyzes the signal delay and relative stability of multilayer graphene nanoribbon (MLGNR) interconnects dependent on temperature at global lengths. A thermally aware driver interconnect load (DIL) system, constituted by equivalent single conductor (ESC) model along with mathematical equations, is proposed to convert multi-conductor transmission circuit into single transmission line of MLGNR. The temperature-dependent analytical delay model of MLGNR is evaluated and the obtained outcomes are compared with the simulated results. The analytical and simulated results are obtained at global interconnect length (2000-[Formula: see text]m) for 32[Formula: see text]nm, 22[Formula: see text]nm and 16[Formula: see text]nm nodes of technology under 200–500[Formula: see text]K temperature range of MLGNR. The simulation and analytical results reveal that the outcomes of the two models correspond well. The trend of the models shows the increase in delay with the rising temperature levels (200–500[Formula: see text]K) for three different nodes of technology. Further, relative stability analysis of MLGNR as interconnect line at three different technological nodes from 500–2000-[Formula: see text]m lengths is examined.

Unsteady aerodynamic force modelling for 3-DoF-galloping of four-bundled conductors

Galloping of overhead transmission lines is characterised by large-amplitude, low-frequency, vertical–horizontal–torsional three degree-of-freedom (DoF) oscillations, which can potentially induce interphase short circuits and fatigue in the conductors and support structures. Numerical analyses are useful for estimating the galloping response of transmission lines, and unsteady aerodynamic forces should be evaluated for accurate simulation. In this study, the unsteady aerodynamic force modelling of four-bundled conductors is investigated based on aerodynamic force measurement test results. Three types of unsteady aerodynamic force measurement tests were performed: under constant torsional angular velocity and under torsional and vertical 1-DoF sinusoidal oscillations. Evaluating the dependence of the aerodynamic forces on the various motions enabled an improved unsteady aerodynamic force model to be developed, considering the effect of angular velocity. First, two-variable aerodynamic coefficients were proposed as a function of the angle of attack and non-dimensional angular velocity. These coefficients were determined via tests performed at constant torsional angular velocities; results with different combinations of wind speed and angular velocity confirmed that the non-dimensional angular velocity can be used to define the unsteady aerodynamic forces. Then, the validity of the two-variable aerodynamic force formulation was confirmed for predicting torsional or vertical 1-DoF oscillations, by comparing the unsteady aerodynamic force obtained via the sinusoidal forced-vibration tests and via the constant angular-velocity tests. Finally, results of the time-history​ analyses using the two-variable aerodynamic coefficients were compared with those of previous wind-response measurement tests to obtain the best unsteady aerodynamic force model for simulating large-amplitude 3-DoF galloping. These results indicate that the unsteady aerodynamic forces for 3-DoF-galloping of four-bundled conductors can be evaluated using the relative angle of attack, the rate of change of the relative angle of attack, and the relative wind speed, using two-variable aerodynamic coefficients measured under constant angular velocity conditions.

Galloping behaviors of ice-coated conductors under steady, unsteady and stochastic wind fields

This paper addresses the similarities and differences between the galloping behaviors of ice-coated conductor transmission lines under steady, unsteady and stochastic wind fields. A finite element model of crescent-shaped ice-coated conductor is first established by using the 3-node isoparametric cable element. The analysis model and numerical integration scheme used in this study are then verified by comparison with the existing experimental data and numerical simulations. In order to efficiently simulate two-dimensional unsteady and stochastic wind fields acting on the ice-coated conductor, the newly-developed spectral representation method based on wavenumber-frequency joint power spectrum is adopted. The probability density evolution method (PDEM) is introduced to explore the statistical characteristics of conductor galloping under stochastic wind field. It is revealed that the unsteady wind field stimulates the self-excited vibration of the ice-coated conductor and further leads to an unstable galloping. However, under the stochastic wind field, the galloping variance of ice-coated conductor is steady and periodic, and the galloping probability density propagates alternately as uni- and bi-modals. These properties are quite different from those exhibited in simplified nonlinear models excited by Gaussian white noises in existing literature. Moreover, the galloping amplitude under stochastic wind field is greatly larger than that under steady wind field. Therefore, an extensive attention should be paid to the safety design of conductor transmission lines in cold regions considering the influence of stochastic wind field.

Numerical Simulation of Galloping Characteristics of Multi-Span Iced Eight-Bundle Conductors

In this article, the numerical model of the multi-span iced eight-bundle conductor is established using the nonlinear finite element method, the galloping of the line under different parameters is simulated, and the tension in the galloping process is analyzed. Based on the aerodynamic characteristics and galloping characteristics of conductors, the galloping modes, frequency characteristics, vibration amplitudes, and galloping orbits of multi-span lines under different wind velocities, span lengths, ice shape, and number of spans are analyzed, compared with those of single-span lines. It is demonstrated that there are differences in galloping characteristics between multi-span transmission lines and single-span lines. Each span of the transmission line is different, so it should be fully considered in the research of galloping prevention and control technology.

Wind-induced tension and deflection of multi-span bundled transmission conductors using aeroelastic model wind tunnel test

An aeroelastic model of the two-span six-bundled conductors is fabricated without distortion of conductors, to investigate the performance of wind-excited multi-span transmission conductors. The wind tunnel test is conducted in a wind tunnel with a big size of cross-section to contain the large aeroelastic model of multi-span transmission conductors and measure wind-induced tension and deflection of the insulator. The effects of wind direction, wind speed, and length of insulator on the wind-induced tension and swing angle of the insulator are then investigated based on the wind tunnel measurement. Results show that the mean transverse tension increases with wind direction θ and follows the law of sin2θ when θ > 40°, but is not proportional to the square of mean wind speed VH when VH < 35 m/s. The force coefficient of the tension decreases with increasing θ and wind speed, and is close to 1.0 when θ = 90° and VH > 35 m/s. Swing angle of the insulator increases with θ and VH, and follows the law of sinθ when θ > 40°. The dynamic response component of the insulator’s swing angle is insignificant when VH > 30 m/s. The length of insulator tends to increase the transverse tension while decrease the swing angle of the insulator. In addition, the wind force coefficient from the aeroelastic model of the two-span conductors is smaller than that specified in GB50545 and GB50655, indicating that these two might overestimate the wind loads on multi-span multi-bundled conductors.

Passive Intermodulation Distortion in Connectors With Nonlinear Interaction in Electrical Contacts and Magnetic Materials

Nonlinearities in electrical contacts and magnetic materials are two main contributors to passive intermodulation (PIM). In this study, mechanisms of thermally induced current truncation and hysteresis effect are introduced to provide explanations for PIM generation and to make predictions for the third-order intermodulation (IM3) products resulting from coaxial connectors. Equivalent circuit models are presented to provide insight into the nonlinear sources both in contact junction and body area with the relative contribution of various physical parameters. The finite element analysis (FEA) model of the central conductor of a DIN-to-N coaxial adapter is developed to identify the current density and temperature distribution in the contact area, while an FEA model of simplified connector cross section is presented to simulate the magnetization effect in the body area. Combined with two nonlinear sources, an equivalent circuit model predicting the PIM behavior is developed. The simulation results show that the material nonlinearity contributes to frequency dependence, while the power dependence is dominated by both nonlinear mechanisms. Connectors with different contact surface are obtained by designed accelerated tests, and two types of connector with different materials are manufactured. Good agreements are observed in experimental measurements, verifying the proposed model of contact&#x2013;material interaction-induced PIM.

A Stable Extended FDTD Thin-Wire Model for Lossy Wire Structures With Irregular Cross Sections

A stable extended FDTD thin-wire model for lossy wire structures with irregular cross sections is presented for lightning transient analysis. In this model, the electro-magnetic field in the vicinity of a conductor with an irregular cross section is taken into account by adopting a single constant correction factor, and the conductor loss is represented with an internal impedance. These two parameters are calculated with a charge simulation method and an equivalent circuit method, respectively. The proposed model is validated in terms of the characteristic impedance, conductor loss and time-domain waveform with analytical and numerical methods. Good agreements are observed. Considering the rigid conductor-size/cell-size requirement and eight tedious convolutional processes in the existing non-circular thin-wire model, the implementation complexity of this proposed model is significantly simplified, and the computational stability is remarkably enhanced. Without reducing the time step, the simulation can maintain its stability when the conductor size varies from 0.01 to 1 of the FDTD cell size. It is also revealed that using a single intrinsic model for conductors with different cross sections could lead to significant calculation errors. Finally, this proposed model is applied for the lightning transient analysis in an electrified railway system.

Numerical study of aeolian vibration characteristics and fatigue life estimation of transmission conductors.

The 2D computational fluid dynamics (CFD) model of transmission conductor is set up to simulate the aerodynamic forces varying with time on the conductor. Taking into account the geometrical nonlinearity of conductor lines, the finite element (FE) models of single span and two-span transmission lines discretized with beam elements are established. By means of the FE models, the aeolian vibrations of the conductor lines excited by the aerodynamic forces under different wind velocities are numerically simulated. The nonlinear resonant characteristics, the amplitude-frequency relations of the conductor lines during aeolian vibration are investigated, and the influences of the span length as well as the initial tension in conductors on the aeolian vibration characteristics are analyzed. Furthermore, a 3D FE model of a conductor segment and the suspension clamp is created to study the stress distributions of the 3D model corresponding to different lines during aeolian vibrations. Finally, based on the stress analysis of the 3D model, the fatigue lives of the transmission conductors during aeolian vibration under different wind velocities are estimated. The jump phenomenon induced by the nonlinear vibration is reflected by the numerical simulation considering the geometric nonlinearity, and it is found that the energy balance principle (EBP) overestimates the vibration amplitudes because it cannot take the influences of the geometrical nonlinearity and span length into account. The obtained results may provide some instructions for the prevention design of aeolian vibration.

Transforming and comparing data between standard SQUID and OPM-MEG systems.

Optically pumped magnetometers (OPMs) have recently become so sensitive that they are suitable for use in magnetoencephalography (MEG). These sensors solve operational problems of the current standard MEG, where superconducting quantum interference device (SQUID) gradiometers and magnetometers are being used. The main advantage of OPMs is that they do not require cryogenics for cooling. Therefore, they can be placed closer to the scalp and are much easier to use. Here, we measured auditory evoked fields (AEFs) with both SQUID- and OPM-based MEG systems for a group of subjects to better understand the usage of a limited sensor count OPM-MEG. We present a theoretical framework that transforms the within subject data and equivalent simulation data from one MEG system to the other. This approach works on the principle of solving the inverse problem with one system, and then using the forward model to calculate the magnetic fields expected for the other system. For the source reconstruction, we used a minimum norm estimate (MNE) of the current distribution. Two different volume conductor models were compared: the homogeneous conducting sphere and the three-shell model of the head. The transformation results are characterized by a relative error and cross-correlation between the measured and the estimated magnetic field maps of the AEFs. The results for both models are encouraging. Since some commercial OPMs measure multiple components of the magnetic field simultaneously, we additionally analyzed the effect of tangential field components. Overall, our dual-axis OPM-MEG with 15 sensors yields similar information to a 62-channel SQUID-MEG with its field of view restricted to the right hemisphere.

Study on Ice - Melting Model and Experimental Verification of Conductor W Ith Carr Ying Direct Current

Study on Ice - Melting Model and Experimental Verification of Conductor W Ith Carr Ying Direct Current

Study on Ice - Melting Model and Experimental Verification of Conductor W Ith Carr Ying Direct Current

Study on Ice - Melting Model and Experimental Verification of Conductor W Ith Carr Ying Direct Current

A Bilevel Multi-Fidelity Polynomial Chaos Approach for the Uncertainty Quantification of MWCNT Interconnect Networks With Variable Imperfect Contact Resistances

With on-chip copper interconnects reaching their performance limits at 22 nanometer technology nodes, multi-walled carbon nanotube (MWCNT) interconnects are projected to replace them below this point. A major aspect of MWCNT interconnect design is to perform uncertainty quantification (UQ) in an efficient yet accurate manner. In this paper, a polynomial chaos (PC) based approach is developed for the UQ of MWCNT interconnect networks under the condition that some shells of each conductor of the network are perfectly contacted while others are imperfectly contacted. The key feature of the proposed approach is the development of a bilevel multi-fidelity algorithm where two different low-fidelity models are combined together. The main outcome of using this bilevel approach is to further reduce the computational time cost of state-of-the-art single level multi-fidelity algorithms, especially in the presence of variable imperfect contact resistances where single level multi-fidelity algorithms fail to provide much speedup over conventional PC approaches. The proposed approach adopts a SPICE hybrid model that combines the features of the equivalent single conductor (ESC) model and the rigorous multiconductor circuit (MCC) model of the MWCNT conductors. Then the low-fidelity ESC model, the intermediate-fidelity hybrid model, and the high-fidelity MCC model are exploited in a bilevel multi-fidelity algorithm for the recovery of the PC metamodel of the interconnect network. This proposed bilevel multi-fidelity algorithm is demonstrably 3-5x more numerically efficient than state-of-the-art single level multi-fidelity algorithms while being even more accurate. Once recovered, the PC metamodel is used to derive all statistical information of the network transient responses.

Parallel-motion-type eddy current damper model of rectangular magnet and conductor

Eddy currents in a conductor moving in a non-uniform magnetic field in a static coordinate system are expressed as the superposition of the term by the partial derivative of the magnetic vector potential with respect to time and by the gradient of scalar potential in a stationary-conductor coordinate system. In this study, we proposed the general equation of “gradient of scalar potential is zero” condition (GSPZ condition) throughout the conductor. Additionally, under satisfying the GSPZ condition, we propose the method of obtaining the magnetic damping force from both the magnetic flux densities and the eddy currents calculated using the Biot-Savart law and Fleming's left-hand rule for the parallel-motion-type eddy current damper (GSPZ-A method). The precision of the GSPZ-A method is similar to that of the three-dimensional finite element method (3D-FEM); however, the effect of the secondary magnetic field was not considered. In this study, the GSPZ condition for the parallel-motion-type eddy current damper of a rectangular magnet and conductor of arbitrary dimensions was established. Furthermore, the GSPZ condition was applied to two types of eddy current dampers—one composed of the single square magnet and the other of the combined square magnet with oppositely aligned magnetic poles. The magnetic damping forces calculated using the GSPZ-A method were compared with those obtained from the 3D-FEM and experiments. As a result, the errors from the GSPZ-A method to 3D-FEM for the single and combined magnets were 10 and 0.4 %, respectively.

ВЛИЯНИЕ ТОПОЛОГИИ ОБЩЕГО ВЫВОДА НА АЧХ ИНТЕГРАЛЬНОГО СВЧ LC-ФИЛЬТРА

The paper describes the developed model of 18 GHz high-pass filter (HPF). The filter model includes models of inductors, MIM capacitors, and conductors allows for skin-effect, edge effects, substrate influence, and the influence of the substrate contacts layout. The developed model has been verified by experimental prototype of the filter, which is made in the standard process of 130 nm silicon-germanium (SiGe) BiCMOS. It has been found that the developed model has cutoff frequency, passband and stopband attenuations, and gain slope close to the experimental prototype. The recommendations of the microwave LC-filters ground conductor layout design are expressed based on developed model.