Passive Conductors Research Articles

Hybrid Checkerboard Metasurface Combining Passive and Active AMCs

In this paper, a hybrid checkerboard metasurface is proposed for controlling radar cross-sections (RCSs) using a small number of active devices. The proposed metasurface consists of passive and active artificial magnetic conductors. The passive metasurface contributes to reducing the RCS level owing to the dispersion characteristics of the checkerboard arrangement, while the active metasurface aids in controlling the RCS. The active RCS pattern of the proposed hybrid checkerboard metasurface in response to changes in phase distribution is also investigated. The results show that the RCS level at the boresight changed from -20.3 dBsm to 4.4 dBsm, and the main lobe of the RCS pattern steered up to 31°. The fabrication and measurement results of the proposed hybrid checkerboard metasurface are also described in this study.

Attenuation of an ultrashort pulse in a folded meander microstrip line with two passive conductors

SummaryIn this article, we investigated a new structure of a protective meander line (ML): a meander microstrip line (MSL) with two passive conductors. The existing theory of ultra‐short pulse (USP) attenuation in MLs is presented for the first time. Based on this theory, we determined the number of decomposed pulses at the output of the MSL line with two passive conductors, and, for the first time, formulated the conditions for pulse decomposition in the line. The folding of the MSL line into non‐core turns was studied in detail. As a result of this article, we proposed a new theory that involves the utilization of additional groups of decomposed pulses for enhanced USP attenuation. These additional groups were thoroughly examined, and the delays of pulses from these groups were defined. This analysis allowed identifying the reason for their appearance. It was revealed that folding the ML into non‐core turns allows further attenuation of the USP amplitude, which increases with the increase of the number of non‐core turns. To validate the obtained simulation results, we performed experimental measurements and obtained good consistency of the results. The N‐norms analysis demonstrated that the combined use of such folding and passive conductors reduces the probability of electrical breakdown, arc discharge, and dielectric breakdown. The maximum USP attenuation at the output was 24.9 dB. As a result of useful signal integrity analysis, it is proposed to use a folded MSL together with a USB 2.0 “Full‐speed” interface with a data transfer rate of 12 Mbit/s. In addition, it is proposed to use such MSLs in DC power circuits.

SIMULATION OF PREMATURE VENTRICULAR CONTRACTIONS IN PATIENT SPECIFIC BIDOMAIN VENTRICULAR MODEL

The goal of the study was to simulate electrical activation of the heart ventricles and corresponding body surface potentials (BSPs) during premature ventricular contractions (PVC) using the patient specific realistic homogeneous model of cardiac ventricles and the torso. Real position of the initial ectopic activation during PVC was determined by intracardial measurement in the upper part of the right ventricle near the His bundle and confirmed by successful catheter ablation of the PVC origin. Simulated electrical activation in the ventricular model was started at the position of the initial ectopic activation as well as at several other sites at various distances from this position. The propagation of electrical activation in the ventricular model was modeled using bidomain reaction-diffusion (RD) equations with the ionic transmembrane current density defined by the modified FitzHugh-Nagumo (FHN) equations. The torso was modeled as a homogeneous passive volume conductor. The RD equations were numerically solved in the Comsol Multiphysics environment. Simulated ECG signals and BSPs were compared with those measured during PVC in a real patient. The polarity and shape of simulated and measured ECG leads as well as the BSP distribution during the PVC were in best agreement when the stimulated region was less than 10 mm from the position of the initial ectopic activation.

Design of passive and structural conductors for tokamaks using thin-wall eddy current modeling

A new three-dimensional electromagnetic modeling tool (ThinCurr) has been developed using the existing PSI-Tet finite-element code in support of conducting structure design work for both the SPARC and DIII-D tokamaks. Within this framework a 3D conducting structure model was created for both the SPARC and DIII-D tokamaks in the thin-wall limit. This model includes accurate details of the vacuum vessel and other conducting structural elements with realistic material resistivities. This model was leveraged to support the design of a passive runaway electron mitigation coil (REMC), studying the effect of various design parameters, including coil resistivity, current quench duration, and plasma vertical position, on the effectiveness of the coil. The REMC is a non-axisymmetric coil designed to passively drive large non-axisymmetric fields during the plasma disruption thereby destroying flux surfaces and deconfining RE seed populations. These studies indicate that current designs should apply substantial 3D fields at the plasma surface during future plasma current disruptions as well as highlight the importance of having the REMC conductors away from the machine midplane in order to ensure they are robust to off-normal disruption scenarios.

Surface-Localized Chemically Modified Reduced Graphene Oxide Nanocomposites as Flexible Conductive Surfaces for Space Applications.

Thermoplastic polymers are a compelling class of materials for emerging space exploration applications due to their wide range of mechanical properties and compatibility with a variety of processing methods, including additive manufacturing. However, despite these benefits, the use of thermoplastic polymers in a set of critical space applications is limited by their low electrical conductivity, which makes them susceptible to static charging and limits their ability to be used as active and passive components in electronic devices, including materials for static charge dissipation, resistive heaters, and electrodynamic dust shielding devices. Herein, we explore the microstructural evolution of electrically conductive, surface-localized nanocomposites (SLNCs) of chemically modified reduced graphene oxide and a set of thermoplastic polymers as a function of critical thermal properties of the substrate (melting temperature for semi-crystalline materials or glass transition temperature for amorphous materials). Selected offsets from critical substrate temperatures were used to produce SLNCs with conductivities between 0.6-3 S/cm and surface structures, which ranged from particle-rich, porous surfaces to polymer-rich, non-porous surfaces. We then demonstrate the physical durability of these electrically conductive SLNCs to expected stress conditions for flexible conductive materials in lunar applications including tension, flexion, and abrasion with lunar simulant. Small changes in resistance (R/R0 < 2) were measured under uniaxial tension up to 20% strain in high density polyethylene and up to 500 abrasion cycles in polysulfone, demonstrating the applicability of these materials as active and passive flexible conductors in exterior lunar applications. The tough, electrically conductive SLNCs developed here could greatly expand the use of polymeric materials in space applications, including lunar exploration, micro- and nano-satellites, and other orbital structures.

Ослабление сверхкороткого импульса в меандровой микрополосковой линии с двумя пассивными проводниками

The results of the analysis of the ultrashort pulse (USP) decomposition into a sequence of pulses in a turn of a meander microstrip line with two passive conductors are presented. Various variants of the terminations of the passive conductors of the turn are considered and the optimal parameters of its cross-section are obtained according to the criterion of the minimum amplitude of the output signal. An analysis of the influence of changes in the geometrical parameters of the line under study on the delays of each decomposition pulses and the USP amplitude at the end of the turn was also made. Conditions for USP decomposition are formulated. The results of optimizing the geometrical parameters of the line, considering the technological capabilities of the company "Rezonit" according to the criteria of USP decomposition and minimizing its amplitude are presented. Also shown the results of folding the line into twenty-one minor turns. It was found that the reducing distance between minor turns enhances signal distortion and reduces its maximum amplitude at the line output. This folding made it possible to significantly reduce the size of the line. Attenuation of the real impact signal from the generator of the S9-11 oscilloscope in different software up to 10.6–16.1 times was obtained.

UAVs Protection and Countermeasures in a Complex Electromagnetic Environment

The study considers the problem of ensuring electromagnetic compatibility of EMI‐based functional destruction means with other radioelectronic equipment as part of a complex for countering unmanned aerial vehicles. To solve this problem, it is proposed to create a methodology that combines a set of diverse approaches and methods. This study focuses on the use of hollow and thin passive conductors, the use of a magnetodielectric in a reflection symmetric modal filter, the use of reflection symmetric structures for decomposing the train of ultrashort pulses (USP), and the use of a meander line as a protective means against USPs. The main results that are expected to be obtained using the proposed approaches and methods are outlined.

PASSIVE LOOP MATHEMATICAL MODEL AS A REDUCTION METHOD FOR OVERHEAD LINE MAGNETIC FIELD

The impact of high voltage overhead transmission and distribution lines on the environment represents a hot topic in the context of transport and distribution of electrical energy. People exposed to magnetic field may lead to health problem. This paper presents a concept of conductor passive loop mitigation as a good solution economically and technically to reduce the AC overhead line magnetic field. This method is applied to the flat distribution line configuration is used medium voltage system. The effect of passive loop conductor on the reduction of magnetic field intensity is further investigated. Numerical results of the magnetic field mitigation and further discussions are provided.

Role of NiO in the nonlocal spin transport through thin NiO films on Y3Fe5O12

In spin transport experiments with spin currents propagating through antiferromagnetic (AFM) material, the antiferromagnet is treated as a mainly passive spin conductor not generating nor adding any spin current to the system. The spin current transmissivity of the AFM NiO is affected by magnetic fluctuations, peaking at the N\'eel temperature and decreasing by lowering the temperature. In order to study the role of the AFM in local and nonlocal spin transport experiments, we send spin currents through NiO of various thickness placed on Y$_3$Fe$_5$O$_{12}$. The spin currents are injected either electrically or by thermal gradients and measured at a wide range of temperatures and magnetic field strengths. The transmissive role is reflected in the sign change of the local electrically injected signals and the decrease in signal strength of all other signals by lowering the temperature. The thermally generated signals, however, show an additional upturn below 100$\,$K which are unaffected by an increased NiO thickness. A change in the thermal conductivity could affect these signals. The temperature and magnetic field dependence is similar as for bulk NiO, indicating that NiO itself contributes to thermally induced spin currents.

Ultrashort pulse decomposition in the turn of a meander microstrip line with a passive conductor

The paper presents the results of evaluating the effect of changing the cross-section parameters of a meander microstrip line (MSL) with a passive conductor on the ultrashort pulse (USP) waveform and amplitude. The study revealed the occurrence of additional pulses in the structure under investigation in addition to cross-talk and main mode pulses. The delays of each pulse were determined and the conditions for USP decomposition in a meander MSL with a passive conductor into a sequence of seven pulses were formulated. By means of heuristic search optimization according to the criteria for fulfilling formulated conditions and the criterion of the minimum amplitude, we obtained the optimal parameters of the line cross-section, at which the USP is decomposed into a sequence of seven pulses with attenuation of 5.38 times relative to half of the electromotive force.

Quasi-static analysis of a two-conductor modal filter with a thin passive conductor

The paper presents the results of the quasi-static analysis of a two-conductor modal filter with a thin passive conductor. The geometrical parameters of the structure under investigation were optimized using a genetic algorithm. The authors performed the quasi-static simulation in the time domain with and without losses. It revealed that with a significant reduction in the thickness of the passive conductor it is possible to preserve or improve the electromechanical properties of the modal filter. The authors showed that in the proposed configuration the difference of per-unit-length delays increased from 0.43 to 0.93 ns, and the maximum output voltage decreased from 501 to 498 mV.

Electrical Characteristics of a Modal Filter With a Passive Conductor in the Reference Plane Cutout

A wider range of operating frequencies, lower supply voltage levels, and increased circuit density of radio-electronic equipment (REE) increase its susceptibility to electromagnetic interferences. Elements of REE are becoming more sensitive to electromagnetic environment especially to ultra-short pulses (USPs) penetrating through front door or back door channels. There is a large variety of noise suppressing devices, but their construction characteristics lead to limited efficiency. Modal filters (MFs), which are based on modal distortion, protect REE from USPs. In this article, the authors present the results of the study of a new method for implementing a MF with a passive conductor in a reference plane cutout and propose two prototypes of the MF with strong and weak couplings. The article presents the results of full-scale and computational experiments in time and frequency domains. For the first time, the decomposition of a USP in the proposed MF configurations is experimentally shown. Besides, we experimentally demonstrated the arrival of additional pulses, the time of which is determined by a linear combination of per-unit-length delays multiplied by the line length. Thus, the proposed approach allows implementing a simple and inexpensive technique for protection against USPs in multilayer printed circuit boards.

Simulation the time response to ultra-short pulse excitation of two cascaded modal filters with a passive conductor in the reference plane

The paper considers protection of radio electronic equipment against conductive excitation of an ultra-short pulse (USP) by using a serial connection of two modal filters (MF) of the same length, which have a passive conductor in the cutout of the reference plane. The amplitude at the output was reduced by 12.5 times in relation to the half of the e.m.f. with 50 Ω resistors at the ends of the passive conductors. The influence of boundary conditions at the ends of the passive conductors of two MFs was considered. For OC-SC, OC-SC the amplitude reduction by 70 times was achieved.

From Symmetry to Asymmetry: The Use of Additional Pulses to Improve Protection against Ultrashort Pulses Based on Modal Filtration

For the first time, the paper considers in a unified work the possibility of the appearance of additional pulses in various structures based on modal filtration technology, which is used to improve protection against ultrashort pulses (USP). We analyzed meander lines (ML) with broad-side coupling, structures with modal reservation (MR), reflection symmetric MLs, and modal filters (MF) with a passive conductor in the reference plane cutout and obtained the following results. It was found that the main reason for the additional pulses to appear in these structures is the introduction of asymmetry (of the cross-section, boundary conditions, and excitation). It is theoretically and experimentally established that additional pulses are a new resource for increasing the efficiency of protective devices with modal decomposition, but the highest effectiveness could be achieved through careful optimization.

Analysis of frequency characteristics of a structure with single modal reservation before and after failure

The paper considers reservation structure implemented by using modal filtering. Such reservation is called modal reservation (MR) for short. To ensure certainty, we took a PCB layout with a single MR. It is shown that in quasi-static simulation, for the structure with losses in conductors and dielectrics, the cut-off frequency for an OC and an SC at one end of the passive conductor is 5.5 and 1.6 %, respectively, lower than for the circuit in operating condition, and the resonance frequencies are 8 and 11.6 %, respectively, lower. In electrodynamic simulation, for the conductor-loss structure and dielectrics, the cut-off frequency for an OC and an SC at one end of the passive conductor is 1.3 and 2.7 %, respectively, lower than for the circuit in operating condition, and the resonance frequencies are 7.3 and 10.65 % lower. The differences of resonance frequencies (f 0), cut-off frequencies (f cu) in quasi-static and electrodynamic simulations are no more than 5.66 and 1.6 %, respectively.

Analysis of stress induced by plasma disruption on vacuum vessel through multi-physics modeling

Abstract The analysis of the stresses induced on the vacuum vessel (VV) of a Tokamak and its internal components by the plasma instabilities, such as plasma disruptions, also following a Vertical Displacement Event (VDE), is one of the major concern in the Tokamak mechanical design. So the availability of a fast simulation tool for evaluating the different design options and also able to perform parametric analysis is highly attractive to define the project requirements and to verify the conceptual design. To respond to this wish, a methodology based on the multi-physics modeling capability offered by the Comsol® software platform was developed. It consists in coupled simulations based on the data sharing between two 2D axisymmetric models, everyone coupled with two corresponding 3D models shifted each other of 10 degrees. In the 2D axisymmetric model of every couple, the magnetic and electric fields generated by the plasma VDE and disruption are calculated imposing the plasma time evolution as input. In the corresponding 3D model only the metallic structures are present and on them the Electric and Magnetic fields are extruded, determining so the induced currents diffusion in the passive conductors. Then the resulting Lorentz’s forces are imposed as body loads on the mechanical structures, so a linear stress analysis can be carried out after the constraints assignment. The same procedure is followed with the second couple of 2D/3D models for check purposes, comparing some proper physical quantities, such as the total induced current flowing on the VV. In this paper the methodology is presented by reporting the simulation of a double null plasma VDE, lasting c.a. 100 ms, followed by a full 5.5 MA plasma current quench in about 40 ms, in a medium size Tokamak intended for experimental research purposes.

Analysis of MHD stability and active mode control on KSTAR for high confinement, disruption-free plasma

Long-pulse plasma operation at high normalized beta, βN, above the n = 1 ideal MHD no-wall stability limit in KSTAR is presently limited by tearing instabilities rather than resistive wall modes. H-mode plasma operation during the recent KSTAR device campaign produced discharges having strong m/n = 2/1 tearing instabilities at βN lower than the ideal MHD no-wall beta limit. The unstable tearing mode consequently reduced plasma confinement and toroidal plasma rotation significantly. The experiment confirmed that an extended duration of electron cyclotron heating (ECH) at the initial phase of the discharge plays a critical role in mode destabilization. To study destabilizing mechanisms that affect the mode growth, the stability of the observed tearing modes from plasmas with significantly different βN is computed by using the resistive DCON code and the M3D-C1 code employing different physics. The computed tearing stability index, Δ′, differs between the mode that is destabilized by the early ECH at lower βN, and the mode that is destabilized at higher βN with observed mode triggering activity. Equilibrium reconstructions that include constraints from internal profile diagnostics are used as input for reliable computation of stability. The modified Rutherford equation (MRE) describing the evolution of the neoclassical tearing mode (NTM) island width has been constructed for KSTAR plasmas by using plasma parameters computed by the TRANSP code. In preparation for long-pulse plasma operation at higher beta utilizing increased plasma heating power, a resistive wall mode (RWM) active feedback control algorithm that includes magnetic sensor compensation of the prompt applied field and the field from the induced current on the passive conductors has been completed and enabled on KSTAR. Use of multiple toroidal sensor arrays is enabled for increased control performance by including the effect of varied mode helicities in the outboard region where the mode measurement is made. This analysis on beta-limiting instabilities and active mode control provides the required foundation for high confinement plasma operation on KSTAR without disruption.

Linking the Cu(II/I) and the Ni(IV/II) Potentials to Subsequent Passive Film Breakdown for a Cu−Ni Alloy in Aqueous 0.5 M NaCl

AbstractCopper and copper–nickel alloys are known to form partially passive films in marine conditions, both naturally and under positive potential bias. Here, the anodic passivation behaviour of copper and of constantan (Cu54Ni45Mn1) as a model for a copper‐nickel alloy are investigated and compared at high positive overpotentials and in 0.5 M NaCl(aq). Abrupt potential‐dependent passive film breakdown is observed for both Cu and Cu−Ni alloys during voltammetry and during chronoamperometry experiments. For Cu, a single transitions occurs at 0.2 V vs. SCE consistent with a Cu(II/I) process, leading to interfacial stress and breaking of a passive CuCl film. For Cu−Ni alloy, two stages are observed at 0.3 V vs. SCE due to a Cu(II/I) process and at 1.7 V vs. SCE due to a sub‐interfacial Ni(IV/II) process. A breakdown mechanism is proposed based on redox processes at the buried interface at the metallic conductor | passive ion conductor junction.

Effect of close coupling on performance of a modal filter with the passive conductor in the reference plane cutout

The improvement of protection against an ultrashort pulse (USP) using a modal filter with the passive conductor implemented in the reference plane cutout is considered. The influence of segmentation on the simulation results is shown. The effect of close coupling on the difference between mode delays and the amplitudes of decomposition pulses was studied. Minimization and alignment of the pulse amplitudes are achieved. The possibility of increasing USP attenuation to 5 times for a given material is shown.

Simple calculation of eddy currents in a long passive conductor

Simple calculation of eddy currents in a long passive conductor