Wire Model Research Articles

Исследование математических подходов к определению частотно-зависимого внутреннего сопротивления провода воздушной линии электропередачи

Mathematical modeling of a power transmission line (PTL) is an important issue for a wide range of tasks in the electric power industry. Mathematical modeling is necessary when studying the transient processes in electric power systems. Analytical expressions that allow modeling power transmission lines in a wide frequency range, including low frequencies and direct current, make it possible to study the operation of relay protection and automation devices in various modes and improve the accuracy of devices of fault location. It is important not only to obtain analytical expressions to determine the frequency dependences of the resistance, but also to verify these expressions in comparison with more accurate methods based on the finite elements method (FEM). The study has been carried out using a mathematical tools based on cylindrical Bessel functions. To develop formulas, it is necessary to determine the constants of integration based on boundary conditions. To verify the obtained expressions, modeling has been performed in the COMSOL Multiphysics software package, which is based on the FEM. The article presents a study of the internal resistance of the wires of power transmission line using the example of AC 185/24 wire. An analytical expression has been obtained to determine the internal complex resistance of a bimetallic wire. The reliability of the obtained expressions is confirmed by the convergence of the simulation results in comparison with the results of simulation modeling in Comsol software and mathematical modeling using known analytical expressions. The proposed approach to determine the internal resistance of a wire makes it possible to get more accurate analytic definition of characteristics of an overhead power transmission line. And thus, to design more qualitative models to analyze transient processes in power transmission lines and investigate the operation of relay protection devices. The wire models developed in Comsol software can be considered as more accurate in a wide range of frequencies.

Design and performance analysis of a novel class of SMA-driven rotational mechanisms/joints

AbstractThe rotational joint plays a vital role in the industrial and civil areas, which is typically utilized to achieve the relative rotation between the adjacent parts. Generally, structuring a conventional rotational joint involves the bulk actuators (e.g., motor and hydraulic cylinders) and complex structures, bringing difficulty for miniaturing the dimension. In this paper, a class of novel rotational mechanisms, which were constructed by the combination of compliant mechanisms (e.g., cartwheel pivot and multileaf pivot) and intelligent actuator (e.g., shape memory alloy (SMA) wire and spring), was proposed to reduce the complexity of the conventional rotational joints. As the case study, a novel SMA wire-driven flexural rotational mechanism (SDFRM), which is constructed by the cartwheel pivot and SMA wire, was developed to demonstrate the feasibility of combining the compliant mechanism and smart actuator. After establishing the static model of the cartwheel pivot and the thermal effect model of the SMA wire, the overall model of SDFRM was developed for the comprehensive performance analysis and the control system design. After that, the model validation and experiments were performed with the proposed prototype and control system. It can be seen from the experimental results that the proposed model can be validated within the error of 3.8%. In addition, the performance study on SDFRM indicates that the prototyped SDFRM system can track the given trajectories within the error of 0.2 mm in the workspace. As a result, the proposed concept was demonstrated as an effective way to reduce the dimension and weight of the conventional rotational joint.

Machine learning-based bridge cable damage detection under stochastic effects of corrosion and fire

This paper proposes a novel machine learning-based cable damage detection model to investigate the upper and lower bounds of bridges’ cable damage degrees under the effects of corrosion and fire. In the proposed approach, the surrogate model for bridge cable damage detection under stochastic effects of corrosion and fire was established by combining machine learning and finite-element analysis to estimate the remaining life of cables. Then the accuracy and generalization performance of three typical machine learning methods for cable damage prediction are compared, such as Back Propagation neural network(BPNN), Radial Basis Function neural network(RBFNN) and Least Square-Support Vector Machine (LS-SVM). It is conducted that LS-SVM owns better prediction accuracy for cable damage under the coupling effects of corrosion and fire than the others. Additionally, the LS-SVM surrogate model combined with stochastic analysis and time-dependent deterioration model of steel wires under corrosion and fire is used to obtain the upper and lower bounds of cable damage under coupling effect of corrosion and fire. The proposed surrogate model can assist management in diagnosing and evaluating cable damage more quickly, efficiently, and flexibly once the real-time monitoring data is obtained. In addition, the surrogate model can guide bridge maintenance in advance.

Tunable Magnonic Chern Bands and Chiral Spin Currents in Magnetic Multilayers.

Realization of novel topological phases in magnonic band structures represents a new opportunity for the development of spintronics and magnonics with low power consumption. In this work, we show that in antiparallelly aligned magnetic multilayers, the long-range, chiral dipolar interaction between propagating magnons generates bulk bands with nonzero Chern integers and magnonic surface states carrying chiral spin currents. The surface states are highly localized and can be easily toggled between nontrivial and trivial phases through an external magnetic field. The realization of chiral surface spin currents in this dipolarly coupled heterostructure represents a magnonic implementation of the coupled wire model that has been extensively explored in electronic systems. Our work presents an easy-to-implement system for realizing topological magnonic surface states and low-dissipation spin current transport in a tunable manner.

Finite element modeling of α-helices and tropocollagen molecules referring to spike of SARS-CoV-2

The newly developed finite element (FE) modeling at the atomic scale was used to predict the static and dynamic response of the α-helix (AH) and tropocollagen (TC) protein fragments, the main building blocks of the spike of the SARS-CoV-2. The geometry and morphology of the spike’s stalk and its connection to the viral envelope were determined from the combination of most recent molecular dynamics (MD) simulation and images of cryoelectron microscopy. The stiffness parameters of the covalent bonds in the main chain of the helix were taken from the literature. The AH and TC were modeled using both beam elements (wire model) and shell elements (ribbon model) in FE analysis to predict their mechanical properties under tension. The asymptotic stiffening features of AH and TC under tensile loading were revealed and compared with a new analytical solution. The mechanical stiffnesses under other loading conditions, including compression, torsion, and bending, were also predicted numerically and correlated with the results of the existing MD simulations and tests. The mode shapes and natural frequencies of the spike were predicted using the built FE model. The frequencies were shown to be within the safe range of 1–20 MHz routinely used for medical imaging and diagnosis by means of ultrasound. These results provide a solid theoretical basis for using ultrasound to study damaging coronavirus through transient and resonant vibration at large deformations.

Prediction and verification of wafer surface morphology in ultrasonic vibration assisted wire saw (UAWS) slicing single crystal silicon based on mixed material removal mode

Monocrystalline silicon slicing is the first step in making chips, and the surface quality of silicon wafers directly affects the quality of later processing and accounts for a large proportion in the chip manufacturing cost. Ultrasonic vibration assisted wire saw (UAWS) is an effective sawing process for cutting hard and brittle materials such as monocrystalline Si, which can significantly improve the surface quality of silicon wafers. In order to further study the formation mechanism of the surface morphology of single crystal silicon sliced by UAWS, a new model for prediction of wafer surface morphology in UAWS slicing single crystal silicon based on mixed material removal mode is presented and verified by experiments in this paper. Firstly, the surface model of diamond wire saw tool is established by equal probability method. Then, the trajectory equation of arbitrary abrasive particles on the surface of wire saw is derived and analyzed. Thirdly, a new model for prediction of the wafer surface morphology based on mixed material removal mode is presented. Finally, the prediction model is verified by UAWS slicing experiment, and the effects of slicing parameters such as wire saw speed, feed speed, and workpiece rotate speed on the surface quality of silicon wafer were studied. It shows that the predicted wafer surface morphology and the experimental wafer surface morphology are similar in some characteristics, and the average error between the experimental and the theoretical values of the wafer surface roughness is 11.9%, which verifies the validity of the prediction model.

Mechanical behavior and recoverable properties of CFRP shape memory alloy composite under different prestrains

This paper explored a prestressed CFRP/SMA composite system, which can be applied to add prestress to the civil structural members. The composite system was composed of carbon fiber reinforced polymer (CFRP) sheets and the embedded shape memory alloy (SMA) wires. The prestress in CFRP sheets was formed by the recovery of SMA wires. Four groups of fully composite (Type I) specimens were fabricated to bear a unidirectional static load to investigate their tensile mechanical properties. Three groups of partial composite (Type II) specimens and five groups of SMA wire specimens were used to study their recoverability. The static test results showed that two main failure modes of the Type I specimens were observed, and the strength of the material was affected by the structural form of the composite. The recovery test results showed that the SMA wire could generate different levels of recovery stress under various amounts of prestrain, and the maximum recovery stress can reach 394.2 MPa for the SMA wire with 6% prestrain by heating it to 131℃. More importantly, the recovery stress can be introduced into the CFRP sheets. In addition, an analytical model for predicting the stress–strain relationship and material strength of the fully composite was proposed, and an improved segmented recovery stress–temperature model of the SMA wire under constraint conditions was also put forward. The results indicated that the calculated values are in good agreement with the experimental values, and the proposed model can effectively predict the mechanical and recoverable properties of the composites.

Numerical analysis on the effect of process parameters on deposition geometry in wire arc additive manufacturing

Here we develop a two-dimensional numerical model of wire and arc additive manufacturing (WAAM) to determine the relationship between process parameters and deposition geometry, and to reveal the influence mechanism of process parameters on deposition geometry. From the predictive results, a higher wire feed rate matched with a higher current could generate a larger and hotter droplet, and thus transfer more thermal and kinetic energy into melt pool, which results in a wider and lower deposited layer with deeper penetration. Moreover, a higher preheat temperature could enlarge melt pool volume and thus enhance heat and mass convection along both axial and radial directions, which gives rise to a wider and higher deposited layer with deeper penetration. These findings offer theoretical guidelines for the acquirement of acceptable deposition shape and optimal deposition quality through adjusting process parameters in fabricating WAAM components.

The Unconditionally Stable Associated Hermite FDTD Method With Thin Wire Modeling

The Unconditionally Stable Associated Hermite FDTD Method With Thin Wire Modeling

Electron correlation and confinement effects in quasi-one-dimensional quantum wires at high density

We study the ground-state properties of ferromagnetic quasi-one-dimensional quantum wires using the quantum Monte Carlo (QMC) method for various wire widths $b$ and density parameters $r_\text{s}$. The correlation energy, pair-correlation function, static structure factor, and momentum density are calculated at high density, $r_\text{s}=0.5$. It is observed that the peak in the static structure factor at $k=2k_\text{F}$ grows as the wire width decreases. We obtain the Tomonaga-Luttinger liquid parameter $K_\rho$ from the momentum density. It is found that $K_\rho$ increases by about $10$\% between wire widths $b=0.01$ and $b=0.5$. We also obtain ground-state properties of finite thickness wires theoretically using the first-order random phase approximation (RPA) with exchange and self-energy contributions, which is exact in the high-density limit. Analytical expressions for the static structure factor and correlation energy are derived for $b \ll r_\text{s}<1$. It is found that the correlation energy varies as $b^2$ for $b \ll r_\text{s}$ from its value for an infinitely thin wire. It is observed that the correlation energy depends significantly on the wire model used (harmonic versus cylindrical confinement). The first-order RPA expressions for the structure factor, pair-correlation function, and correlation energy are numerically evaluated for several values of $b$ and $r_\text{s} \leq 1$. These are compared with the QMC results in the range of applicability of the theory.

Impact of the Vehicle Environment on the Thermal Behavior of the Electrical Wiring

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The thermal behavior of wires within the electrical distribution system (EDS) has a strong impact on the conductor cross section, the type of insulation, the derating, and the fusing system, and therefore on weight, cost, and reliability. Consequently, significant efforts have been made to develop sound static and dynamic thermal models for single wires and wire bundles. However, these models are based on the simplifying assumption that the object is completely surrounded by air, where, with the exception of free convection, airflow can be neglected, and where no interaction with other objects is considered.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;The approach presented in this paper takes into account the actual environment and routing within a vehicle, where some objects such as metal sheets can be considered as heat sinks and other objects, e.g. a motor block, as heat sources. For this reason, measurements were performed using an experimental set-up that allows any desired positioning and alignment of the DuT (device under test, here: wire, cable, bundle) and of two temperature-controlled heat source/sink objects. These objects are a large rectangular surface and a small sphere, in order to be able to emulate as many spatial configurations as possible. The overall set-up is protected against externally-induced airflows. Because the exact modelling of the heat transfer processes (radiation, conduction, and free/forced convection) would require time-consuming FEM calculations for the investigated complex geometries, a simplified and partially data-driven model is proposed. The paper describes the theory and the modeling approach, and presents initial simulation and measurement results.&lt;/div&gt;&lt;/div&gt;

The current magnetization hypothesis as a microscopic theory of the Ørsted magnetic field induction

A wire that conducts an electric current will give rise to a circular magnetic field (the Ørsted magnetic field), which can be calculated using the Maxwell–Ampere equation. For wires with diameters in the macroscopic scale, the Maxwell–Ampere equation is an established physical law that can reproduce a range of experimental observations. A key implication of this equation is that the induction of Ørsted magnetic field is a result of the displacement of charge. A possible microscopic origin of Ørsted magnetic induction was suggested in [J. Mag. Mag. Mat. 504, 166660 (2020)] (will be called the current magnetization hypothesis (CMH) thereupon). The present work establishes computationally, using simplified wire models, that the CMH reproduces the results of the Maxwell–Ampere equation for wires with a square cross section. I demonstrate that CMH can resolve the apparent contradiction between the observed magnetic field and that predicted by the Maxwell–Ampere equation in nanowires, as was reported in [Phys. Rev. B 99, 014436 (2019)]. The CMH shows that a possible reason for such contradiction is the presence of non-conductive surface layers in electric conductors.

Development of a novel 3D-printed and silicone live-wire model for thyroidectomy

PurposeWe present the development and validation of a novel and innovative low-cost model for thyroidectomy. The purpose is to provide a high-fidelity and inexpensive method to provide repetition to surgeons early on the learning curve. Materials and methodsThe model consists of a 3D-printed laryngeal and tracheal framework, with silicone components to replicate the thyroid gland, strap muscles, and skin. A copper wire models the recurrent laryngeal nerve and is circuited with a buzzer to indicate contact with instruments. Thirteen resident trainees successfully completed the simulated thyroidectomy after viewing an instructional video. Face validity of the model was assessed with a 19-item 5-point Likert scale survey. Subject performance was assessed using a checklist of procedure steps. ResultsParticipant feedback indicated enthusiasm for realism of the recurrent nerve (4.46 average Likert rating, 5 indicates strong agreement), dissection of the nerve (4.15), use of the buzzer (4.69), and overall satisfaction (4.46). Soft tissue components scored poorly including realism of the skin (3.08), thyroid gland (3.31), and mobilization of the lobe (3.23), identifying aspects to improve. All participants reported increased confidence with thyroid surgery after using the model; this was most pronounced among junior residents (1.5 ± 0.76 versus 3.13 ± 1.13; p = 0.016). ConclusionThyroidectomy requires repetition and volume to gain competence. Use of the simulator early in training will provide confidence and familiarity, to enhance the educational value of subsequent live surgery.

Theoretical study on sawing force of ultrasonic vibration assisted diamond wire sawing (UAWS) based on abrasives wear

Wire saw cutting of monocrystalline silicon plays an important role in semiconductor manufacturing. The study of wire saw cutting silicon is important, and the grain wear has a great effect on the saw cutting force. Therefore, in this paper, considering abrasive wear on the wire saw, the ultrasonic vibration assisted sawing force theoretical model from a single abrasive to multiple abrasives is established. With the application of equal probability method, the surface profile model of wire saw is established. According to the abrasive wear law of wire saw, the finite element model (FEM) of wire saw with different abrasive wear is established. The influence of different abrasive wear on sawing force and workpiece surface morphology is analyzed by Abaqus. Finally, the experimental verification is carried out. The experimental results show that the sawing force of the ultrasonic vibration assisted diamond wire sawing (UAWS) decreases by 38% on average than that of the conventional diamond wire sawing (CWS), the surface roughness value is reduced, and the surface morphology is improved. With the increase of the abrasive wear value, the sawing force and the numbers of pits firstly decrease and then increase, the surface roughness value distribution firstly concentrates and then disperses, and the scratches show a smooth to intermittent trend.

Thermal Modal Performance of Composite Laminates Embedded with Anti-Symmetric Oblique Coupling Gradient Pre-Strained SMA Wires for Suppressing Resonance

As an extension of conventional gradient, anti-symmetric oblique coupling gradient has a superior modal modification ability on composite laminates embedded with pre-strained shape memory alloys (SMA) wires, which is beneficial to suppress modal resonance of composite laminates in the thermal environment. This paper presents an anti-symmetric oblique coupling gradient model of SMA along the thickness direction. That is, the gradient model of SMA wires’ orientation and the positive and negative gradient model of SMA volume fraction. Considering the internal force of composite laminates composed of the pre-strain recovery force of SMA and the thermal expansion force of the substrate, the free vibration equation of composite laminates with additional internal forces energy is derived from first-order shear plate theory and Hamilton principle. The influence of coupling gradient parameters on the thermal modal performance of SMA composite laminates is analyzed and verified by experiments. The proposed anti-symmetric oblique coupling gradient SMA wires’ distribution form effectively exerts the recovery stress generated by SMA tensile pre-strain, i.e., effectively improves the stiffness and critical buckling temperature. Coupling gradient distribution broadens the frequency modulation range, which makes the fine regulation of the natural frequency and critical buckling temperature feasible.

Visual Haptic Feedback for Training of Robotic Suturing.

Current surgical robotic systems are teleoperated and do not have force feedback. Considerable practice is required to learn how to use visual input such as tissue deformation upon contact as a substitute for tactile sense. Thus, unnecessarily high forces are observed in novices, prior to specific robotic training, and visual force feedback studies demonstrated reduction of applied forces. Simulation exercises with realistic suturing tasks can provide training outside the operating room. This paper presents contributions to realistic interactive suture simulation for training of suturing and knot-tying tasks commonly used in robotically-assisted surgery. To improve the realism of the simulation, we developed a global coordinate wire model with a new constraint development for the elongation. We demonstrated that a continuous modeling of the contacts avoids instabilities during knot tightening. Visual cues are additionally provided, based on the computation of mechanical forces or constraints, to support learning how to dose the forces. The results are integrated into a powerful system-agnostic simulator, and the comparison with equivalent tasks performed with the da Vinci Xi system confirms its realism.

Crack tip fields in a fiber-reinforced hyperelastic sheet: Competing roles of fiber and matrix stiffening

Fiber-reinforced materials are widely observed in biological tissue such as human arteries and tendons. Characterizing the influence of fibers on crack-tip fields in such nonlinear materials undergoing large deformation is an important precursor to understanding damage evolution and fracture or tearing. In this paper, we present asymptotic crack tip fields in a fiber-reinforced hyperelastic sheet and explore the competing roles of fiber and matrix stiffening. A generalized neo-Hookean model and a power-law model are employed to characterize the behavior of the matrix and fibers, respectively. We show that the asymptotic crack-tip fields are mainly determined by the phase with largest degree of stiffening. For example, when the stiffening effect of fibers is much larger than that of the matrix, the crack tip fields are determined by the constitutive behavior of fibers, and the wire model and the fabric model reasonably characterize the deformation and stress near the crack tip. On the contrary, if the matrix stiffening is larger than that of the fibers, we show that the crack tip fields approach those of a pure matrix material. The asymptotic results are complemented by finite element simulations which show good agreement. These findings may shed light on material damage at a crack tip in fiber reinforced materials.

Research and development of discharge free insula-tion of wires for space application

The present research aimed to investigate a charging of the cylindrical insulation layer of wires for space applications under the influence of isotropic electron radiation with an electron injection uniform in the volume of the dielectric. An analytical solution of the first-order differential equation resulting from the proposed charging model is obtained. A software has been developed and received state registration that allows for a complete calculation of the physical parameters of space-application wires resistant to electrification effects. The obtained results are proposed to be used for modeling and testing of wires for space applications in order to completely exclude the physical possibility of the occurrence of electrostatic discharges (ESR) of the &amp;quot;insulation-core&amp;quot; type during the operation (of the spacecraft) in orbit during geomagnetic disturbances in the Earth's magnetosphere. Keywords: electricity, bulk charging, insulation, dark conductivity, electrostatic discharge.

Исследование и разработка безразрядной изоляции проводов космического применения

The present research aimed to investigate a charging of the cylindrical insulation layer of wires for space applications under the influence of isotropic electron radiation with an electron injection uniform in the volume of the dielectric. An analytical solution of the first-order differential equation resulting from the proposed charging model is obtained. A software has been developed and received state registration that allows for a complete calculation of the physical parameters of space-application wires resistant to electrification effects. The obtained results are proposed to be used for modeling and testing of wires for space applications in order to completely exclude the physical possibility of the occurrence of electrostatic discharges (ESR) of the "insulation-core" type during the operation (of the spacecraft) in orbit during geomagnetic disturbances in the Earth's magnetosphere.

A straightforward method to quantify the electron-delocalizing ability of π-conjugated molecules.

Electronic delocalization is essential to the properties of π-conjugated molecules. We introduce the inter-fragment delocalization index (IFDI) as an easy-to-use computational method for quantifying the electronic delocalization in π-conjugated oligomers and molecular wire models. We show that the IFDI is related to the torsion barriers of π-conjugated dimers, and to the single-molecule conductance of several π-conjugated fragments. The IFDI is a useful screening technique for comparing different π-conjugated subunits as components in organic electronics, since it can quantify the influence of substitution position, structure, and (anti)aromaticity on delocalization.