Continuous Pulses Research Articles

Research on Fault Feature Extraction Method of Rolling Bearing Based on SSA–VMD–MCKD

In response to the problem that nonlinear and non-stationary rolling bearing fault signals are easily disturbed by noise, which leads to the difficulty of fault feature extraction, to take full advantage of the superiority of variational mode decomposition (VMD) in noise reduction, and of maximum correlation kurtosis deconvolution (MCKD) in highlighting continuous pulses masked by noise, a method based on sparrow search algorithm (SSA), VMD, and MCKD is proposed, namely, SSA–VM–MCKD, for rolling bearing faint fault extraction. To improve the feature extraction effect, the method uses the inverse of the peak factor squared of the envelope spectrum as the fitness function, and the parameters to be determined in both algorithms are searched adaptively by SSA. Firstly, the parameter-optimized VMD is used to decompose the fault signal to obtain the intrinsic mode function (IMF) components, from which the optimal mode component is selected, and then the optimal component signal is deconvoluted by the parameter-optimized MCKD to enhance the periodic fault pulses in the optimal component signal, and finally extracts the rolling bearing fault characteristic frequency by envelope demodulation. Experiments on simulated signals and measured data show that the method can adaptively determine the parameters in VMD and MCKD, enhance the fault impact components in the signals, and effectively extract the fault characteristic frequencies of rolling bearings, with a success rate up to 100%, providing a new idea for rolling bearing fault feature extraction.

Analysis of the failure mode of surge protector under multi-pulse lightning strikes and its mechanism

This paper proposes a special disconnector for surge protector (SPD) with the ability to pass large pulse currents under multiple pulses, which has been verified to solve the problem of SPD fire and combustion under multiple pulses in engineering applications. The safety problem caused by the lightning strike failure of SPD has always been a difficult research point in low-voltage power distribution systems, especially the failure mechanism under multi-pulse lightning strike is still unclear. In this paper, the multi-pulse lightning generator is used to simulate the multi-pulse lightning current to carry out the SPD lightning impulse test. The results show that the SPD will have short-circuit breakdown and fire and combustion under multi-pulse lightning strikes, mainly because the continuous pulses will generate energy superposition, and the built-in disconnector and external disconnector fuses and circuit breakers cannot effectively cooperate with the SPD, and there is a protection blind spot. As a result, the SPD cannot be quickly detached at the moment of a short circuit. Based on the thermal effect of multi-pulse lightning strikes, a multi-pulse SPD special disconnector is designed, which can effectively solve the problem of lightning strike ignition of SPD under multi-pulse lightning strikes, and is of great significance to the lightning protection safety of low-voltage power distribution systems.

Midfrequency acoustic propagation and reverberation in a deep ice-covered Arctic ocean.

A model-based analysis of sound transmission in a deep ice-covered Arctic ocean recorded during the Ice Experiment 2014 is presented. A source of opportunity transmitted mid-frequency (3500 Hz) 5 s duration continuous wave pulses. The source and receiver were omnidirectional, located under ice at a ∼30 m depth at a ∼719 m distance from each other. Recorded acoustic intensity time series showed a clear direct blast signal followed by an about 30 s duration reverberation coda. The model considers several types of arrivals contributing to the received signal at different time intervals. The direct signal, corresponding to a short-range nearly horizontal propagation, is strongly affected by the presence of a weak near-surface (within 50 m depth) acoustic channel. Reverberation coda that follows the direct signal corresponds to medium-range bottom- and ice-bounced arrivals from steep angles which are controlled by reflectivity and scattering strengths of ice and bottom, their physical properties, and acoustical parameters.

Realizing fast temperature measurement and simulating Maxwell’s demon with nearly nondestructive detection in cold atoms

Optical detection and manipulation of the thermal properties is an essential subject of cold atoms in the quantum era. For laser cooled alkali atoms, we have experimentally realized deterministic temperature measurement with time cost below 1 ms and effective filtering of colder atoms with temperature less than 1 μK, with the help of nearly nondestructive detection. The quick temperature measurement is accomplished by carefully resolving the diffusion dynamics of atoms with the information provided by a single probe laser pulse in the form of bucket detection, while suppressing the amplitude and phase noises of probe laser. The separation of colder atoms is attainable as the velocity differences of atoms translate into nontrivial position differences, when the diffusion sustains for a few tens of milliseconds. In particular, these efforts are based on a labeling process that distinguishes the cold atoms under study from the others by specific internal states, while the nearly nondestructive detection is implemented via driving a cycling transition with continuous optical pulses. Moreover, such a position-dependent labeling process can be further modified to become velocity-dependent, with which we have demonstrated a Maxwell’s demon-type operation on cold atoms, as Maxwell’s demon’s intricate abilities can be understood as measuring the velocity of an individual particle and then performing feedback according to a straightforward dichotomy of the velocity value.

Dense γ-ray emission in two consecutive pulses irradiating near critical density plasma

We report the overdense electron acceleration and dense gamma ray emission via the use of two continuous laser pulses irradiating near critical density plasma. Thanks to the ion channel formed behind the first laser pulse, the leading laser beam is well focused to a higher intensity. As a result, the noticeable electron re-injection and ion focusing when one laser incident is significantly suppressed in the two-consecutive- lasers scheme, efficiently improved the electron acceleration process. Moreover, owing to the stronger laser field and the higher electron energy, the probability rate of the accelerated electron emitting γ-rays is considerably enhanced. In this regime, the laser intensity is reduced from to W cm−2 with the competitive density of generated gamma rays.

Experimental Study of Inductive Pulsed Power Supply Circuit With Residual Energy Recovery Branch

Inverse current commutation with semiconductor devices (ICCOS) has been proved to be able to shut off the high current of inductors. Inductive pulsed power supply (IPPS) is considered to have great potential in the field of Electromagnetic Launch (EML) due to its high energy density and fast discharge speed. A repetitive IPPS circuit with ICCOS technique has been proposed based on a high-temperature superconducting pulsed power transformer (HTSPPT) in our previous studies. This circuit can recover the remaining energy and generate continuous current pulses. However, due to the low voltage of the primary power supply, the circuit uses the primary power supply to recover the remaining energy, resulting in a slower process of recovering the remaining energy. For this issue, this article proposes a method to improve the original circuit by adding a residual energy recovery branch on the secondary side. The new circuit can recover most of the remaining energy on the secondary side through a designated capacitor. The working process of this circuit is illustrated detailed in this article, and the preliminary simulation verification is carried out. To further study the feasibility of this circuit, an experimental platform was built with a small HTSPPT. Experimental results and comparative analysis show that the new circuit has better characteristics in terms of remaining energy recovery and increasing pulse amplitude.

Light-induced thermomagnetic recording of thin-film magnet CoFeB on silicon waveguide for on-chip magneto-optical memory.

Thermomagnetic recording is a technique used as a writing process for magneto-optical (MO) drives. Despite their significant advantages, such as rewritability, nonvolatility, reliability, and large cycling endurance, MO drives are rarely used today because of the complex drive systems that must deal with magnetic field and lightwave simultaneously. This study reports on the light-induced thermomagnetic recording of a ferromagnetic thin-film CoFeB on a Si photonic platform. Lightwave guided in the Si waveguide evanescently coupled to the thin-film magnet and underwent optical absorption, resulting in heating and a decrease in coercive force. Therefore, we observed magnetization reversal with an applied magnetic field for both continuous and modulated light pulses using a magneto-optical Kerr effect microscope, and the light-induced thermomagnetic recording was experimentally demonstrated on a Si photonic platform. The proposed scheme enables the realization of on-chip MO memories on the Si photonic platform in which neither bulky free-space optics nor mechanical rotation systems are required.

Ultrafast metamaterial all-optical switching based on coherent modulation.

We report a demonstration of an ultrafast all-optical switching with unique light control effects. The all-optical switching consists of a gold film with asymmetric split rings and a silica substrate. The device effectively controls the transmission and absorption of continuous pulses in the communication band (1200-1800 nm) and short pulses with a pulse duration of 80 fs by using the interaction of two coherent beams on nano-metamaterials with a thickness of only 50 nm. The metamaterial can achieve more than 90 % output control under continuous light irradiation. When the pulse duration is 80 fs, the switching contrast ratio is greater than 3 : 1 and the modulation bandwidth is greater than 12.5 THz. Switching time can be on the order of femtosecond. This paper provides a new structure for ultra-high speed optical data processing components in coherent networks.

Photothermal phenomenon: Extended ideas for thermophysical properties characterization

The photothermal phenomenon involves material photon heating in the form of continuous waves, modulated waves, or pulses. The resulting temperature rise carries very rich information about the material's structures and thermophysical properties. This review is constructed to cover some of the extended ideas of the photothermal phenomenon for measuring a material's thermophysical properties and interface thermal conductance/resistance. For frequency-domain photothermal phenomena, the photoacoustic (PA) and photothermal radiation (PT) techniques provide great ways to measure coatings and suspended samples, which can also be measured using the laser flash and time-domain thermoreflectance (TDTR) techniques. Thermal probing based on electrical thermal sensing is successfully implemented in the transient photo-electro-thermal (TPET) and pulsed laser-assisted thermal relaxation (PLTR) techniques, which significantly extend the capability of laser flash technique to micro/nanoscale 1D structures. The energy transport state-resolved Raman (ET-Raman) is distinct from traditional techniques in its material-specific thermal sensing capability and integral way of ultrafast thermal sensing. Detailed physics discussions are provided for all these techniques, including their advantages and limitations. Still, large development rooms exist for the relatively new techniques, including TPET, PLTR, and ET-Raman. These include measurements under extreme situations, sensitivity improvement, and distinguishing conjugated physical processes.

Recent Progress and Development Trend of Self-Sweeping Fiber Laser

Since 2011, when Kir’yanov et al. first reported a new wavelength self-sweeping ytterbium-doped fiber laser that does not rely on any tuning element but only on the dynamic induced grating generated in the gain fiber by the standing wave resonator structure, the self-sweeping effect based on fiber waveguides has been extensively studied, leading to great progress in fundamental physics and other applications of self-sweeping fiber lasers. Different doped fiber lasers have not only achieved the self-sweeping effect, but also observed new phenomena such as anomalous self-sweeping and continuous pulses. Due to their remarkable spectral and pulsed characteristics, self-sweeping fiber lasers have been widely used in spectral detection, fiber sensing and short pulse synthesis. In this paper, we will introduce the classification of different doped self-sweeping fiber lasers, summarize their different implementations, and introduce their self-sweeping laws, pulse characteristics, recent progress of applications and future development prospects.

Efficacy of add-on bilateral transcranial magnetic stimulation with a double-cone coil in patients with treatment resistant depression and comorbid anxiety: Evidence from real-world clinical practice.

Abstract Background/Objectives: Repetitive transcranial magnetic stimulation is an effective adjuvant therapy to treat depression. Recently developed double-cone shape coils could stimulate deeper regions in the brain. There is limited evidence about the efficacy of double-cone coil stimulation in patients with treatment resistant depression and comorbid severe anxiety. This study is aimed to provide preliminary evidence of efficacy of Intermitent Theta Burst over the left dorsolateral prefrontal cortex (DLPFC) followed by 1Hz over the right DLPFC on improving symptoms of depression and anxiety in a naturalistic setting. Methods: Over a 2-year period, 38 outpatients (26 male and 12 female) were recruited from "Instituto de Neuroestimulación de Lima" diagnosed with treatment resistant depression (baseline PHQ-9 ≥ 10) and severe anxiety (baseline Hamilton Rating Scale for Anxiety ≥ 20 [HAM-A]). The average of previous failed treatments was 3.92 (SD=1,74). An average of 22.26 daily sessions were scheduled over a month to deliver Theta burst triplets at 85% of resting motor threshold followed by continuous pulses of 1Hz at 120% resting motor threshold for a combined total of 29 minutes and 46 seconds using a Neuro-MSX device from Neurosoft. Pharmacological treatment used was categorized by therapeutic drug class. The average number of concomitant medications taken during bilateral rTMS treatment was 2.79 (SD=1,09). Results: 76.3% (n=29) achieved response by reducing at least 5 points in PHQ-9 scale while 47,3% (n=18) achieved response to anxiety symptoms (at least 50% reduction HAM-A). Response rate was higher among patients with increased severity at baseline (p=0.002). Although the study was not powered to find differences in concomitant treatments, patients receiving benzodiazepines (n=17) showed less decline in depression symptoms (p=0.048). Conclusion: Sequential bilateral rTMS using a double-cone coil improved depression and severe anxiety symptoms. Benzodiazepines might impair response to treatment and this should be confirmed with sham-controlled studies and larger samples. Keywords: Bilateral rTMS, Double-cone coil, Treatment resistant depression, Severe Anxiety

Carbon Nanofiber/PEDOT Based Macro-Porous Composite for High Performance Multifunctional Neural Microelectrode

Brain study methods mainly rely on neurochemical detection and electrophysiology, respectively to study the molecular dynamics [1] and electrical activity [2] in the brain cellular environment. Since the brain functioning relies on careful orchestration of both neurotransmitter and neuroelectric activities, coupled monitoring of them holds great promise in elucidating the brain functioning mechanisms and its related diseases e.g. Parkinson’s, epilepsy, etc [3]. Most of the conventional implantable neural interfacing technologies are comprised of noble metals on silicon/ polymer substrates. They suffer from inferior electrical properties, mechanical tissue-electrode mismatch, incompatible surface area, and low signal-to-noise ratio [4]. To address the need, researchers around the world are developing innovative soft materials with multimodal functionalities, especially the organic flexible materials such as conductive polymers and carbon allotropes, to fuel the next-generation multimodal neural electrode devices [5].Here in this work, we present a new macro-porous, conductive, and stable nanocomposite, made up of carbon nanofibers (CNFs) and PEDOT polymer, coated on a flexible neural microelectrode array (Fig. 1A-B). A fully controlled one-shot electrodeposition strategy was developed using chronopotentiometry technique, to coat flexible Au-microelectrode surfaces with macro-porous CNF/PEDOT nanocomposite. The oxidized CNFs were used as a dopant and infused within the conductive PEDOT, electrochemically, in such a way that their excellent electronic, mechanical, chemical properties, and resulting combined performances can be exploited to yield better quality neural recordings, electrical stimulation and neurotransmitter detection. At first, CNFs were oxidized to be dispersible in water (unlike raw CNFs) by vortex and sonication. Later, CNF/PEDOT composite was deposited on Au-electrodes galvanostatically, resulted in a 3D porous and fibrous network (Fig. 1B-D). Then, CNF/PEDOT deposits were characterized through electrochemical impedance spectroscopy (EIS) and pulse current injection. The composite microelectrodes showed low impedance, 16 ± 2 kΩ for a typical electrode area of 1250 µm2, at 1kHz (value corresponding to the neuron firing frequency) (Fig. 1E). Voltage transient responses were measured, at continuous 1ms-biphasic current pulses (cathodic first) in biologically relevant aCSF media, resulted in a charge-injection limit value of 7.6 ± 1.3 mC/cm² (Fig. F). Among all reported organic nanostructured composite materials that were deposited on flexible metallic substrates, CNF/PEDOT displayed superior electrical properties and charge injection capabilities [5]. Next, the capability of CNF/PEDOT composite electrode for in-vitro Dopamine (DA) sensing was evaluated by chronoamperometry, at 130mV vs SCE (oxidation potential of DA). The current responses submitted to DA injections resulted in linear regression (Fig. 1G, R²>0.99), with a high sensitivity of 13.4pA/nM.µm², compared to similar electrochemical sensors [6]. Overall, these electrodes displayed excellent electrical properties: low impedance (16 ± 2 MΩ.µm2 at 1 kHz) and high charge injection capabilities (7.5 ± 1.3 mC/cm²) making them promising candidates for bidirectional electrophysiology, while being capable to detect neurotransmitters like dopamine. Finally, integrated upon flexible neural probes, these composite microelectrodes were tested in-vivo on mouse brain slices as recording and stimulating electrodes (Fig. 1H). They displayed excellent performances, being capable to record spontaneous activities of neurons (sharp wave-ripples and single unit action potentials) and allowed to stimulate electrically the brain slice tissues, to obtain safe and stable evoked potentials. The obtained results show a great prospect for CNF/PEDOT composites for developing next-generation microelectrodes for applications in neural therapies.Figure 1. (A) Optical micrograph of flexible neural probe. (B) CNF/PEDOT deposition on 4 Au-microelectrodes of the implant. SEM images, (C) top view and (D) cross-sectional view of the composite electrode. (E) EIS measurement on modified microelectrodes from 10 Hz to 7 MHz in aCSF at 0V Vs Ag/AgCl. (F) Voltage transient of a CNF/PEDOT microelectrode resulting from the injection of a biphasic current pulse (90 µA with 1 ms pulse width). (G) Linear regression curve of CNF/PEDOT electrode current response at 130mV vs SCE to dopamine injections. (H) Electrophysiological recordings in the hippocampal region (CA1 and CA3) of a mouse brain slice, using flexible microelectrode array modified with CNF/PEDOT composite.AcknowledgmentsAgence Nationale de la Recherche (ANR-15-CE19-0006 and ANR-19-CE19-0002-01) and French RENATECH network.References Lama R.D., Karl Charlson, Arun Anantharam, Parastoo Hashemi, Analytical Chemistry, 84(19): p 8096-101 (2012).Normann R.A. and E. Fernandez, Journal of Neural Engineering, 13(6): p 061003 (2016).Ledo A., Cátia F. Lourenço, João Laranjinha, Greg A. Gerhard, and Rui M. Barbosa, Analytical Chemistry, 89(22): p 12383-12390 (2017).Enming Song, Jinghua Li, Sang Min Won, Wubin Bai, and John A. Rogers, Nature Materials, 16, 590-603 (2020).Zaid Aqrawea, Johanna Montgomeryb, Jadranka Travas-Sejdicc,d, Darren Svirskis, Sensors and Actuators B, 257,753–765 (2018)Jong-Min Moon, Neeta Thapliyal, Khalil Khadim Hussain, Rajendra N.Goyal, Yoon-Bo Shim, Biosensors and Bioelectronics, 102 , 540-552 (2018). Figure 1

Tunable Multilevel Data Storage Bioresistive Random Access Memory Device Based on Egg Albumen and Carbon Nanotubes.

In this paper, a tuneable multilevel data storage bioresistive memory device is prepared from a composite of multiwalled carbon nanotubes (MWCNTs) and egg albumen (EA). By changing the concentration of MWCNTs incorporated into the egg albumen film, the switching current ratio of aluminium/egg albumen:multiwalled carbon nanotubes/indium tin oxide (Al/EA:MWCNT/ITO) for resistive random access memory increases as the concentration of MWCNTs decreases. The device can achieve continuous bipolar switching that is repeated 100 times per cell with stable resistance for 104 s and a clear storage window under 2.5 × 104 continuous pulses. Changing the current limit of the device to obtain low-state resistance values of different states achieves multivalue storage. The mechanism of conduction can be explained by the oxygen vacancies and the smaller number of iron atoms that are working together to form and fracture conductive filaments. The device is nonvolatile and stable for use in rewritable memory due to the adjustable switch ratio, adjustable voltage, and nanometre size, and it can be integrated into circuits with different power consumption requirements. Therefore, it has broad application prospects in the fields of data storage and neural networks.

A Medium Power, Self-Sustaining, and Configurable RF Pulse Generation Circuit Using a Nonlinear Transmission Line and Power Amplifier in Open and Closed-Loop Configurations

Nonlinear transmission lines (NLTLs) are a class of pulse forming networks (PFNs) for modulation of pulsed power to generate radio frequency (RF) signals. Primarily, NLTL designs assume a two-port configuration, which requires ones-to-tens of nanosecond input pulse rise time for each modulated pulse out. In this article, a closed-loop or single-port pulser that yields continuous pulses based on prior pulse stimulation is presented. The pulser is comprised of an NLTL, a power amplifier (PA), and a solid-state HV pulse generator. The capability advantage of the closedloop system is its stability and center frequency tunability. Pragmatically, the solid-state-based design of this system enhances its probability of fielded use due to volume and mass savings compared to the prior art. The validity of the proposed design is empirically shown by a 16-section NLTL coupled with a solid-state laterally diffused metal-oxide-semiconductor (LDMOS)-based PA and a custom HV pulse generator. The closed-loop configuration constructed from these components demonstrated a peak power of 2.1 kW into 50 Ω at 90 MHz. This is the first report of a solid-state switch-based closed-loop NLTL configuration capable of producing a continuous pulse stream. Furthermore, we propose a dual-diode-based NLTL design, which can operate and output at higher center frequencies compared to its single-diode counterpart.

Ns-pulsewidth pulsed power supply by regulating electrical parameters for AFM nano EDM of nm-removal-resolution

Nano electro discharge machining (nano EDM), as a frontier processing method in the research stage of exploration, has an important application prospect in the machining of metal and alloy materials for achieving nanoscale removal resolution. A pulsed power supply used in nano EDM is expected to limit a single pulse energy to nJ order of magnitude for improving the removal resolution of single pulsed discharge even to nanoscale. One developing direction is to decrease pulsewidth of the pulsed power supply. Conventional pulsed power supplies hardly output a single pulse and continuous pulses with nanosecond (ns) pulsewidth, resulting in too large single pulsed energy of μJ order of magnitude usually. In this research, a novel pulsed power supply is designed for realizing the ns-pulsewidth with controllable pulsewidth and peak voltage. The key novelty lies in a cascaded circuit with two triodes working in the state of ultra-fast avalanche conduction, where pF capacitors are applied to adjust the pulsewidth and pulsed energy precisely. Performance tests verified that a single pulse of 5 ns pulsewidth or continuous pulses up to 9 MHz can be outputted. Furthermore, nano EDM experiments of single pulsed discharge are carried out under the conditions of nanometer (nm) discharge gap and nm-tip tool electrode based on an atomic force microscope (AFM) system. The special results are achieved: a single pulsed energy can reach down to 1.75 nJ by outputting a pulsewidth of 10 ns, and a nano-EDM crater is only about 182 nm in diameter with regular shape and little recasting. Those results verify the possibility of AFM-tip-based nano EDM for machining nanostructures.

Study on the pulse parameters of fast periodic pulsed reactor under stable operation

The fast periodic pulsed reactor utilizes rotating reflectors to introduce periodic varying reactivity, making the core generate continuous power pulses at a certain frequency. The pulse parameters under stable operation are extremely important in measuring the performance of the reactor. The critical search method of calculating the pulse parameters is established, and in order to further study the factors affecting the pulse parameters,a new theoretical estimation method is proposed. The two methods are verified in the IBR-2 with PuO2 as fuel, and the results are in good accordance with the experimental data. The fast periodic pulsed reactor FNPR with UO2 as fuel is designed. The pulse parameters of FNPR are calculated by the verified methods and compared with those of IBR-2. The results show that in terms of parameter quality, FNPR is inferior to IBR-2. The method of improving FNPR pulse parameters is also discussed herein.

Continuous Sub-THz Repetition Rate CEP-Stable Ultrashort Laser Pulses Generation via Coherent External Fabry-Pérot Cavity

An optical setup comprising an external Fabry-Pérot (FP) cavity that maintains ultrashort pulse spatial and temporal coherence, is proposed to generate continuous sub-terahertz repetition rate ultrashort pulses (USP). Analytical results from different sets of pulse-to-pulse carrier-envelop phase offset (Δφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CEO</sub> ) output conditions manifest the possibility to extract and utilize the reflected USP signal from an ultrastable Pound-Drever-Hall phase-locked external FP cavity to stabilize or reset the Δφ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CEO</sub> to 0 or multiple of 2πrad in real time. The generation of a steady, ultrahigh repetition rate output, from a low repetition rate ultrashort pulse laser requires management of carrier-envelope phase (CEP). The CEP management with the passive external FP cavity group delay dispersion control enables transition from usual quasi- to continuous repetition rate. The net control and management of these parameters allow the passive external FP cavity multiplication factor to be increased above 200.

Density reduction on plasma sheath using pulsed magnetic field

When a space vehicle travels through the atmosphere at a hypersonic speed, it is enveloped by a plasma sheath. The density of plasma sheath is high enough such that communication and telemetry signals are prevented from passing to and from the vehicle, which is called communication blackout. A method to reduce plasma density for communication blackout mitigation by using pulsed magnetic field is proposed in this paper. In order to study the effect of pulsed magnetic field on plasma density, a two-dimensional axisymmetric model was established. The simulation results suggested that the pulsed magnetic field can reduce the plasma sheath density of 5 cm thickness by more than 90%, and was of sufficient size (about 5 cm) and time duration (about 330 μs) to permit transmission of data. On the basis of the simulation results, the interaction mechanism between pulsed magnetic field and plasma is explained by theoretical analysis. Furthermore, experiments of the plasma density reduction by pulsed magnetic field are performed. The experimental results suggested that a 0.55T pulsed magnetic field can reduce the plasma sheath density of 14 cm thickness by 43%–78%, which verifies the effectiveness of the pulsed magnetic field method. A comparison of results from simulation and experiment provided strong evidence for the correctness of the simulation model. The simulation results also show that low pressure and high initial electron density are beneficial to the reduction of plasma density, which also explains the phenomenon in the experiment. In addition, it is found in the experiment that two continuous reverse pulses can play the same role in reducing the plasma density, which provides the possibility for the continuous reduction of plasma density. These investigations could have a significant benefit on the design and optimization of pulsed magnetic field mitigation scheme for the blackout problem.

Radar High-Resolution Range Profile Ship Recognition Using Two-Channel Convolutional Neural Networks Concatenated with Bidirectional Long Short-Term Memory

Radar automatic target recognition is a critical research topic in radar signal processing. Radar high-resolution range profiles (HRRPs) describe the radar characteristics of a target, that is, the characteristics of the target that is reflected by the microwave emitted by the radar are implicit in it. In conventional radar HRRP target recognition methods, prior knowledge of the radar is necessary for target recognition. The application of deep-learning methods in HRRPs began in recent years, and most of them are convolutional neural network (CNN) and its variants, and recurrent neural network (RNN) and the combination of RNN and CNN are relatively rarely used. The continuous pulses emitted by the radar hit the ship target, and the received HRRPs of the reflected wave seem to provide the geometric characteristics of the ship target structure. When the radar pulses are transmitted to the ship, different positions on the ship have different structures, so each range cell of the echo reflected in the HRRP will be different, and adjacent structures should also have continuous relational characteristics. This inspired the authors to propose a model to concatenate the features extracted by the two-channel CNN with bidirectional long short-term memory (BiLSTM). Various filters are used in two-channel CNN to extract deep features and fed into the following BiLSTM. The BiLSTM model can effectively capture long-distance dependence, because BiLSTM can be trained to retain critical information and achieve two-way timing dependence. Therefore, the two-way spatial relationship between adjacent range cells can be used to obtain excellent recognition performance. The experimental results revealed that the proposed method is robust and effective for ship recognition.

Mafic to intermediate composition intrusions from the Kahak area, central Urumieh-Dokhtar arc of Iran: transition from Eocene to Miocene intra-arc extensional magmatism

Several gabbro, gabbroic diorite, and diorite intrusions were emplaced in the Neotethyan Urumieh-Dokhtar magmatic arc in the Kahak area of the Zagros Orogen. The plutonic rocks intruded Cenozoic volcanic and pyroclastic succession. U-Pb dating via LA-ICP-MS of zircon yields early to middle Eocene ages of ~53 to 38 Ma for the diorite and gabbroic diorite in Veshnaveh and Naragh areas and Miocene ages of 23 to 20 Ma for gabbroic rocks in the Kerogan and Fordou areas. The Eocene magmatic phase occurred quite possibly as three continuous pulses. The Eocene and Miocene intrusions have negative Nb-Ta anomalies like those of subduction-related magmas. The Pb isotopic compositions show the involvement of subducted sediment in the source of the studied samples. The Eocene intrusions are tholeiitic and enriched in incompatible-trace-elements (especially the HFSE) compared to the Miocene intrusions which are calc-alkaline and have lower concentrations of most incompatible trace elements. Sr-Nd isotopic compositions of the Eocene rocks lie close to the mantle array and near Bulk Silicate Earth, but the Miocene suite is shifted to higher (87Sr/86Sr)i. The higher (87Sr/86Sr)i, along with larger Ba, K, Pb, and Sr anomalies, in the Miocene suite imply more slab fluid input and/or crustal contamination. Apparently, the Eocene mafic magmas formed in slightly metasomatized sub-continental lithospheric mantle (SCLM), whereas the Miocene suite was derived from highly metasomatized, deeper levels of the SCLM. We suggest that slab roll back occurred between the Eocene and Miocene and transferred the location of mantle partial melting to greater depths.