Pulse Phenomena Research Articles

The Impact of Pulse Plasma Treatment on the Operating Characteristics of Steel 40X10C2M: Experiment and Numerical Simulations

This paper presents a study of operating characteristics of steel 40X10C2M after treatment it of high-energy plasma pulses. The steel is used to manufacture the elements of ships' power plants. For pulsed plasma treatment of steel samples, we used an electrothermal plasma accelerator (ETPA). A high-current pulsed high-pressure arc discharge was initiated in a restricted dielectric chamber of ETPA. The discharge duration was 1.4 ms, the maximum current reached the value of 5 kA, the discharge voltage was up to 5 kV. We investigated the microhardness and microstructure of the processed (modified) layer and determined the optimal parameters of steel processing that provide the best characteristics of the modified layer when the microhardness increases by ≈ 5 times. Microhardness maxima were discovered in the depth of the modified layer. The paper studies the possibilities of controlling the maxima localization to form the desired performance characteristics of the treated layer. Mathematical modeling of rapid pulsed heating of the steel surface layer is performed within the framework of the two-phase "melt-solid" model, taking into account the dynamics of the thermodynamic characteristics of steel. For this purpose, we used the classical equation of thermal conductivity with varying steel parameters: density, heat capacity, and coefficient of thermal conductivity during the transition of a substance from the liquid to the solid phase. Within the chosen mathematical model, numerical calculations of the rapidly pulsed heating phenomenon of the steel surface were performed, taking into account melting and solidification in the Comsol Multiphysics package using the finite element method. The numerical simulation results are in good agreement with the experimental distribution of the microhardness of the treated steel layer deep into the sample.

Understanding Substrate-Guided Assembly in van der Waals Epitaxy by in Situ Laser Crystallization within a Transmission Electron Microscope.

Understanding the bottom-up synthesis of atomically thin two-dimensional (2D) crystals and heterostructures is important for the development of new processing strategies to assemble 2D heterostructures with desired functional properties. Here, we utilize in situ laser-heating within a transmission electron microscope (TEM) to understand the stages of crystallization and coalescence of amorphous precursors deposited by pulsed laser deposition (PLD) as they are guided by 2D crystalline substrates into van der Waals (vdW) epitaxial heterostructures. Amorphous clusters of tungsten selenide were deposited by PLD at room temperature onto graphene or MoSe2 monolayer crystals that were suspended on TEM grids. The precursors were then stepwise evolved into 2D heterostructures with pulsed laser heating treatments within the TEM. The lattice-matching provided by the MoSe2 substrate is shown to guide the formation of large-domain, heteroepitaxial vdW WSe2/MoSe2 bilayers both during the crystallization process via direct templating and after crystallization by assisting the coalescence of nanosized domains through nonclassical particle attachment processes including domain rotation and grain boundary migration. The favorable energetics for domain rotation induced by lattice matching with the substrate were understood from first-principles calculations. These in situ TEM studies of pulsed laser-driven nonequilibrium crystallization phenomena represent a transformational tool for the rapid exploration of synthesis and processing pathways that may occur on extremely different length and time scales and lend insight into the growth of 2D crystals by PLD and laser crystallization.

Analysis of a computer model of a power supply system for agricultural consumers in a single-phase ground fault mode

On the basis of the constructed computer model, the process of a single-phase earth fault in the power supply system of agricultural consumers with a dead-grounded neutral was studied. As a result of the analysis of the model of the power supply system in the single-phase short circuit mode, the phenomenon of a sharp-pointed voltage pulse of negative polarity, arising at the moment of protection operation, was revealed, which negatively affects the electrical equipment of agricultural consumers.

A Single-pulse Study of PSR J1022+1001 Using the FAST Radio Telescope

Abstract Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded ∼105 single pulses from PSR J1022+1001. We studied the polarization properties, their energy distribution, and their times of arrival. This is only possible with the high sensitivity available using FAST. There is no indication that PSR J1022+1001 exhibits giant pulse, nulling, or traditional mode changing phenomena. The energy in the leading and trailing components of the integrated profile is shown to be correlated. The degree of both linear and circular polarization increases with the pulse flux density for individual pulses. Our data indicates that pulse jitter leads to an excess noise in the timing residuals of 67 ns when scaled to one hour, which is consistent with Liu et al. We have unsuccessfully trialed various methods to improve timing precision through the selection of specific single pulses. Our work demonstrates that FAST can detect individual pulses from pulsars that are observed in order to detect and study gravitational waves. This capability enables detailed studies, and parameterization, of the noise processes that affect the sensitivity of a pulsar timing array.

A Coupling Method for Identifying Arc Faults Based on Short-Observation-Window SVDR

This article presents a new method for effective detection of ac series arc fault (AF) (SAF) and extraction of SAF characteristics in residential buildings, which addresses the challenges with conventional current detection methods in discriminating arcing and nonarcing current due to their similarity. Different from the traditional method, in the proposed method, the differential magnetic flux is coupled to obtain high-frequency signals by putting the live line and the neutral line through the current transformer, which can effectively solve the problem of SAF features disappearing in the trunk-line current. However, similar to the traditional method, the effectiveness of the proposed coupling method could also be compromised when being used in cases with dimmer load and load starting process. This is found to be caused by the presence of high-amplitude pulse phenomenon in the nonarcing signals in these scenarios, which are incorrectly detected as arcing signals in other loads. To address this issue, a short-observation-window singular value decomposition and reconstruction algorithm (SOW-SVDR) is used to enhance the capability to identify SAFs by the coupling method. The proposed method has been implemented and validated according to the UL1699 standard with different types of loads connected to the system and also tested under their starting processes. The experimental results show that the proposed approach is more effective in detecting AFs compared with existing methods.

Progress in the arc plasma temperature measurement and its finite element analysis in pulsed MIG welding process

The article focuses on the state of the art review of progress in the arc plasma temperature measurement, a lesser-explored area of pulsed metal inert gas welding because of technological and economic constraints. However, investigation of the arc plasma temperature is paramount for precise prediction in welding process simulation models. The dynamic behavior of arc plasma in the pulsed MIG welding process is a multifaceted heat mass transfer phenomenon involving chemical, electro-magnetic, and fluid dynamics.In the pulsed MIG welding process thermal, mechanical, and electrical phenomenon co-exists and results in the formation of all four states of matter in a very small fusion sphere. The paper throws light on the latest investigations on the importance of precise measurement of arc plasma temperature, techniques used for measurement of the arc plasma, and challenges associated with pulsed MIG welding. Moreover, unanswered characteristics of the welding fusion sphere with future directions are discussed in the challenges section. It will serve as a guide to researchers and industry for developing better insight for performing pulsed MIG welding, developing accurate numerical models of pulsed MIG welding, and will also provide sufficient base to focus on thrust area of pulsed MIG welding.

Recent Developments in High Power EM (HPEM) Standards With Emphasis on High Altitude Electromagnetic Pulse (HEMP) and Intentional Electromagnetic Interference (IEMI)

Standardization of High Power Electromagnetic (HPEM), environments, protection design and test methods is becoming increasingly important particularly as the perceived risk to society from HPEM is growing. Many generic standards and some application or product specific standards are now available. This letter will provide an overview of some recent developments in HPEM standards, in particular High Altitude Electromagnetic Pulse (HEMP) and Intentional Electromagnetic Interference (IEMI) phenomena.

Oil Metal Debris Detection Sensor Using Ferrite Core and Flat Channel for Sensitivity Improvement and High Throughput

A high throughput and high sensitivity sensor for detection of oil metal debris is presented. The sensor is mainly composed of a planar coil, a ferrite core and a flat channel. The adoption of flat channel can increase the throughput without sacrifice of sensitivity. The comparative experiments show that the ferrite core not only eliminates the phenomenon of multiple pulse peaks for detecting individual metal particle in the flat channel, but also can improve the sensitivity of inductance detection and resistance detection. For detecting 130-140 μm iron particles, the inductance amplitude and SNR (signal-to-noise ratio, the SNR is the amplitude divided by the interference noise) of sensor with ferrite core are 1.17 times and 1.22 times higher than those of sensor without ferrite core, respectively. For detecting 160-170 μm copper particles, the inductance amplitude and SNR of sensor with ferrite core are 1.24 times and 1.28 times higher than those of sensor without ferrite core, respectively, and the resistance amplitude and SNR of sensor with ferrite core are 1.09 times and 1.07 times higher than those of sensor without ferrite core, respectively. In addition, the introduction of resistance detection can increase the ability of sensor to detect non-ferromagnetic metal particles. We can detect iron particles with diameter of 40 μm onwards and detect copper particles with diameter of 90 μm onwards using the sensor with ferrite core combined with inductance and resistance detection methods. This work improves the throughput of microfluidic high-precision detection, which can provide technical support for large-flow oil detection.

A new model for nulling and moding in radio pulsars

AbstractSingle pulse behaviour of radio pulsars is usually interpreted in terms of the E × B drift of a radio beam. It is shown that antisymmetric arrangement of the radio-bright zones can produce several types of observed single pulse phenomena: the half-cycle jump in subpulse modulation phase, left-right-middle subpulse sequence and switching between the core-dominated and cone-dominated pulsation modes. The geometry can also produce nulling, both sporadic and intermodal. The model implies that the radio-quiet intervals that separate the main pulse and interpulse in PSR B0826−34 correspond to azimuthal breaks in the radio beam, instead of breaks in colatitude.

Implications of high-power electromagnetic (HPEM) environments on electronics

High-Power Electromagnetic (HPEM) environments can be considered to encompass lightning, Nuclear Electromagnetic Pulse (NEMP) and High-Power Radio Frequency (HPRF) phenomena including Directed Energy (DE) and Intentional Electromagnetic Interference (IEMI). HPEM environment definitions are now maturing and are now described in a variety of published standards. Methods to evaluate the effects on electronic systems and an understanding of effects mechanisms are perhaps less mature but this is a vibrant area of research. Due to a variety of factors described in this article protection and resilience of critical infrastructure from HPEM environments is becoming a pressing need.

New optical explicit plethora of the resonant Schrodinger’s equation via two recent computational schemes

This research paper investigates the computational solutions of the resonant Schr?dinger?s equation. The modified Khater method and Adomian decomposition method are applyied for construct new analytical traveling and semi-analytical wave solutions. This model describes the pulse phenomena and studied in non-linear optics. For further illustration of our obtained solutions, some distinct types of sketches are given.

New optical explicit plethora of the resonant Schrodinger’s equation via two recent computational schemes

This research paper investigates the computational solutions of the resonant Schr?dinger?s equation. The modified Khater method and Adomian decomposition method are applyied for construct new analytical traveling and semi-analytical wave solutions. This model describes the pulse phenomena and studied in non-linear optics. For further illustration of our obtained solutions, some distinct types of sketches are given.

Pulsation Characteristics of Corona Discharge in Electrohydrodynamic Process Using Ionic Liquid

In this study, the pulse phenomenon is found in the electrohydrodynamic (EHD) process using an ionic liquid, which is similar to other liquids, but there are significant differences in pulse characteristics. The frequency, waveform, charge, and images of the pulse in the EHD process with the ionic liquid are studied experimentally. The results show that the pulse process is divided into two stages: a low-frequency pulse stage and a high-frequency pulse stage. We propose that the pulse is caused by the air corona discharge and the frequency is influenced by the anchoring radius of liquid oscillation in the electric field. The different anchoring radii of the two stages are the main reason for the obvious difference in the frequency. The main difference between the ionic liquid and other solutions is the conductivity and the surface tension coefficient, which is the cause of corona discharge rather than electrospray.

Selective weakening of mineralised synthetic particles by high voltage pulses

The phenomena of high voltage pulse (HVP) selective breakage and HVP weakening have been reported separately in the literature, but the relation between the two HVP applications has previously not been investigated. Synthetic particles made of Epirez high strength grout were cast with and without embedded metalliferous minerals of chalcopyrite and pyrite and used in a study of HVP selective breakage and weakening. When metalliferous grains were embedded in the grout, there were added either as a single grain occurrence or as a fine disseminated texture. The HVP products were assessed using the JKRBT breakage characterisation method for the mineralised particles and the barren particles (with no metalliferous minerals contained), respectively. It has been found that the HVP weakening effect mainly occurs in the mineralised particles, with a reduction in particle competence (indicated by the relative change in A × b value) between 172% and 200% for the pyrite fines dispersed synthetic particles, and 70% relative reduction for the single chalcopyrite grain embedded synthetic particles. The barren synthetic particles do not exhibit a statistically significant weakening effect and appear much more competent than the mineralised particles after HVP treatment. This finding suggests that in mineral processing circuit design utilising the HVP technology, benefits associated with HVP weakening on the downstream comminution process would be maximised by combining the HVP pre-concentration and weakening applications, in doing so removing the barren unweakened rocks from the process.

PECULIARITIES OF THE MANIFESTATION AND INFLUENCE ON THE ELECTROMAGNETIC PROCESSES OF THE TRANSIENT SKIN EFFECT IN METAL CONDUCTORS WITH PULSED CURRENT

Purpose. Preparation of brief scientific review of basic results of the known theoretical researches of the electrophysics phenomenon of linear transient skin effect (TSE) in the non-magnetic homogeneous massive conductors of flat and cylindrical configurations on which in the discharge electric circuits of high-voltage electrophysical installations (EPHI) the pulsed currents ip(t) flow with given amplitude-temporal parameters (ATPs). Methodology. Theoretical bases of electrical engineering, bases of theoretical electrophysics, electrophysics bases of technique of high-voltage and high pulsed currents. Results. The brief scientific review of results of the known theoretical researches of the electrophysical phenomenon of linear TSE in non-magnetic homogeneous massive flat and cylindrical metal conductors with pulsed axial (azimuthal) current ip(t), formed in the discharge circuit of powerful high-voltage EPHI. In the generalized and systematized form the basic features of manifestation of linear TSE in the indicated conductors and influence of the considered skin effect on electromagnetic processes are presented at flow in conductors and discharge circuit of a high-voltage EPHI with the pulsed current ip(t) time-varying by law of attenuated sinewave. Influence of linear TSE is described in non-magnetic massive conductors during transient in a discharge circuit of EPHI with the pulsed current ip(t) of given ATP, depth of penetration of the electromagnetic field in materials of the indicated conductors, own integral electric parameters of the considered conductors and their good quality in the high-current discharge circuit of high-voltage EPHI. It is shown that at the analysis of electromagnetic transients in high-current discharge electric circuits of powerful high-voltage EPHI it is necessary to take into account flowing in materials of the examined massive conductors of such known electrophysical phenomenon as linear TSE. Originality. Generalization and systematization is first executed regarding domestic and foreign scientists-electrical engineers’ results of theoretical researches for long-term period of the electrophysics phenomenon of linear TSE in the flat and cylindrical metallic conductors of different thickness with the pulsed current ip(t)of given ATP. Practical value. The results presented in the generalized and systematized form will be useful for electrical engineers in deepening of understanding of basic features of manifestation in non-magnetic massive homogeneous conductors with the pulsed current ip(t) of given ATP of such widely widespread in area of high-voltage high-current pulsed technique electrophysics phenomenon as linear TSE and its influences on electromagnetic transients in similar metallic conductors and high-current discharge circuits of high-voltage EPHI.

Structure of optical solitons of resonant Schrödinger equation with quadratic cubic nonlinearity and modulation instability analysis

The resonant nonlinear Schrödinger equation (NLSE) having quadratic-cubic nonlinearity for describing pulse phenomena and studied in nonlinear optics. In this work, we achieved optical solitons and solitary waves solutions of resonant NLSE with nonlinearities of quadratic and cubic by employing F-expansion method. In engineering and applied physics, these solutions have important applications. The stability of model is examined by employing the analysis of modulation instability, which shows that the obtained exact solutions are stable. We also given the movement of some achieved solutions graphically, which facilitates to recognize the physical interpretation of this complex nonlinear model. The achieved results confirm that this method is powerful and easy in applying.

A multiphysics analysis of the strain energy in multicellular environments

This letter considers the strain energy distribution in cell assemblies. Our scalable model consists of N-core-shell spherical structures modeling biological cells with assumptions based on two fundamental premises. First, we use a finite element in the framework of time-domain to solve for the electrodeformation and cell electroporation when a well-defined electrical stimulus is delivered to a multicellular environment. Second, the strain-stress response of the cell assemblies is characterized by a relaxation time which is much larger than the time constant of the membrane charging. A “switch off” (corresponding to times after electrical pulsing) phenomenon observed in the strain energy signal might provide an interesting discriminant test capable of providing different information on the proximity (coupling) effect between cell and assembly anisotropy depending on the type of electrical stimulus employed. In the explicit examples we study, we learn up to date facts about how the local enhancement of the electric field, deformation of the cell, strain energy, and relative area occupied by the pores are modified by varying the intercellular distance distribution.

Existence of solution, pulse phenomena and stability criteria for state-dependent impulsive differential equations with saturation

This paper discusses the problem of the state-dependent impulsive differential equations (SDIDE) with saturation. First, the existence of solution for the system and some sufficient conditions which can be guaranteed every solution intersecting each impulsive surface exactly once are derived. Second, combining with comparison principle and some inequality techniques, we give some local quasi-exponential stability for SDIDE with saturation. Moreover, this paper proposes some succinct results by comparing to those for fixed time impulsive dynamical systems. Finally, some examples with simulations are given to demonstrate the effectiveness of our results.

New Perspectives on the Physical Origin of Acoustic Wood Anomalies

Acoustic Wood anomaly is a pulsed ultrasound phenomenon in which sharp spectral anomalies such as tips or dips or both occur in the spectrum of a pulse reflected from or transmitted through a periodically corrugated interface for normal incidence. To date only surface acoustic waves generated on periodic interface through diffraction mechanism have been identified as the physical source of these spectral anomalies, and each anomaly has been proved being matched by specific order(s) of diffraction of related surface wave(s) with high accuracy. However, in this study, we report the observation of several anomalies that are not originated from surface waves, and an anomaly that cannot be matched by any individual order of diffraction. Using a proposed sectional analysis approach, comb filtering effect is proved to be a new source of spectral anomalies, and a multiple surface wave theory is developed not only to provide a satisfactory explanation for the unusual anomaly observed, but also to serve as a general guideline for understanding spectral anomaly formation.

Energy accumulation mechanism in pulsar magnetospheric plasma eigen-waves and formation of Giant Radio Pulses

In the present work we consider energy accumulation mechanism in relativistic electron-positron plasma in the magnetosphere of pulsars. Waves propagating almost across the magnetic field lines are generated that accumulate the energy of plasma particles, as the waves stay significantly long in the resonance region. The accumulated energy is transmitted in the parallel direction of the magnetic field lines as soon as the non-linear plasma processes start to operate. It is suggested that exit of the accumulated energy via waves propagating along the magnetic field lines matching the viewing angle of the observer produces giant pulses. It is shown that these waves come in the radio domain, explaining the Giant Radio Pulse phenomenon.