Yazhou Chen

Army Engineering University, China · National Key Laboratory on Electromagnetic Environment Effects

Detecting small ship targets in large-scale synthetic aperture radar (SAR) images with complex backgrounds is challenging. This difficulty arises due to indistinct visual features and noise interference. To address these issues, we propose a novel two-stage detector, namely a convolutional and visual transformer fusion network (CViTF-Net), and enha...

The complex electromagnetic environment makes the electromagnetic susceptibility (EMS) test challenging for the unmanned aerial vehicle (UAV) data link. The EMS test can be regarded as an optimization problem to obtain the maximum signal-to-interference ratio that makes the data link losing lock. In this article, we proposed an adaptive EMS test de...

Tweek atmospherics are extremely low frequency and very low frequency pulse signals with frequency dispersion characteristics that originate from lightning discharges and that propagate in the Earth–ionosphere waveguide over long distances. In this study, we developed an automatic method to recognize tweek atmospherics and diagnose the lower ionosp...

A twisted three-wire cable model with uniform twisting characteristics is proposed in this paper, and its terminal response under external electromagnetic wave irradiation is calculated using the TLM method based on Taylor model. The triple-stranded triple-helix structure is determined in the method and the parametric equations of the twisted wire...

In this work, a multi-task convolutional neural network with multi-input (MIMT-CNN) is proposed for electromagnetic interference (EMI) signals recognition and electromagnetic environment risk evaluation of the data link of unmanned aerial vehicle (UAV). The visualized performance parameters, short-time Fourier transform (STFT) spectrograms, and con...

Most current research on commonly used distributed computing frameworks neglects the difficulty of learning these frameworks. These commonly used distributed computing frameworks are designed for professionals, and users must understand them well to use them for calculation tasks. In order to solve the challenging balance problem between versatilit...

Noncontact surface potential measurement approaches with high spatiotemporal resolution are suitable for insulating and conducting materials and have the advantages of noninvasiveness and high sensitivity. These methods show promising application prospects in fields, such as material surface charge imaging. However, reduced electrode size leads to...

The electrostatic field in the space excited by a thunderstorm cloud reflects the trend of the spatial potential and has a great influence on the selection of lightning discharge paths. Some studies have used an approximate method to calculate the electrostatic field excited by a thunderstorm cloud, but the error is still relatively large. In order...

In this article, a novel method is presented for electromagnetic interference (EMI) perception and electromagnetic susceptibility (EMS) assessment of an unmanned aerial vehicle (UAV) against interference. A large number of in-phase and quadrature data of the UAV's data link and their corresponding critical EMI signal were collected by the equivalen...

Unmanned aerial vehicle (UAV), when illuminated by high-power microwave (HPM), is vulnerable to losing control and even falling to the ground with damage. To explore the mechanism of the UAV's falling and its damage caused by HPM, the HPM radiation experiments on a certain kind of UAV are carried out. It is concluded that the UAV's cable is the mai...

At present, the research on the tracking performance of navigation receivers is based on the conditions of single-frequency interference, however, the space electromagnetic environment is complicated, and so it is necessary to study the effect of the navigation receiver under multifrequency interference. Through the analysis of the blocking interfe...

Polymer nanocomposites can serve as promising electrostatic shielding materials; however, the underlying physical mechanisms governing the carrier transport properties between nanofillers and polymers remain unclear. Herein, the structural and electronic properties of two polyethylene/graphene (PE/G) interfaces, i.e., type-H and type-A, have been s...

An intelligent antenna synthesis method is proposed to automatically select suitable antenna type and provide optimal geometric parameters according to the requirement of antenna performance. The performance characteristics of different antennas are analyzed, and a smart antenna selection model is established to recommend the appropriate antenna by...

In this study, structural and electronic properties of two-dimensional hybrid ZnO/graphene (ZnO/G) and ZnO/graphene/graphene (ZnO/G/G) nanocomposites are investigated based on first-principles calculations. The calculation indicates that interlayers of the two nanocomposites exist typical van der Waals (vdW) weak interactions. The intrinsic electro...

Aiming at the problem that satellite navigation signals are easily interfered by the radio frequency (RF) pulse signal, the electromagnetic interference effect of RF pulse on the navigation receiver is studied in this paper. A mathematical model of the pulse interference signal is established, and we choose the bit error rate (BER) as an indicator...

Target detection in aerial images taken by unmanned aerial vehicles is the most widely used scene at present. Compared with ordinary images, the background of aerial images is more complex, and the target size is smaller, which results in inferior detection precision and a high false detection rate. This paper proposes a new small target detection...

The detection of an electromagnetic pulse (EMP) field is of great significance in determining the field environment of tested equipment in small spaces. Finger-shaped miniature optical fiber sensors for electromagnetic pulse field measurement were designed. The antenna of a weak field sensor was integrated with a shielding shell, and the wire welde...

With the rapid development of science and technology, UAVs (Unmanned Aerial Vehicles) have become a new type of weapon in the informatization battlefield by their advantages of low loss and zero casualty rate. In recent years, UAV navigation electromagnetic decoy and electromagnetic interference crashes have activated widespread international atten...

The calculation of electric field in space excited by thunderclouds is an important basis for lightning warning and protection. In numerical calculation of the electromagnetic field, it is often necessary to perform multiple loop nesting calculations on several triple integrals, which consume a lot of computing resources. In order to shorten the ca...

Ultra-wideband (UWB) pulse signal has an extremely narrow pulse width and wide frequency bandwidth, which overlaps with the operating frequency band of Global Position System (GPS) receivers, posing a potential threat to their performance. In response to this problem, through mathematical analysis and software simulation, the effects of UWB pulse s...

The datalink of an unmanned aerial vehicle (UAV) is vulnerable to external electromagnetic interference (EMI). The characteristic parameters of the EMI signal can be definitively detected by a developed monitoring platform mounted on the UAV, but it is impossible to determine the lost-link thresholds of the datalink in any state by experiment becau...

Electrical field induced conductive switching materials are novel nonlinear materials. They can show an abrupt reduction of resistivity when the external electrical field strength exceeds a predefined threshold, and the materials will switch from insulated state to conductive state. In this letter, a novel time-domain response characteristics test...

the present research is carried out on the issue that the BDS (BeiDou Navigation Satellite System) receiver exerts some vulnerability to CW (continuous wave) interference. The analysis on the interference mechanism of navigation signal is implemented based on the model of direct sequence spread spectrum communication system while the method of para...

The data link is an important guarantee for the Unmanned Aerial Vehicle (UAV) equipment to complete its battlefield functions. Its anti-electromagnetic pulse interference capability directly affects the airborne communication security. Ultra-wideband (UWB) electromagnetic pulse has become an important source of electromagnetic interference due to i...

Unmanned aerial vehicle (UAV) is likely to be interfered by high-power microwave (HPM) pulse, especially its datalink. To investigate the effects of HPM pulse on the datalink of a UAV in a dynamic flight scenario, a tracking interference model for an HPM source toward a UAV is proposed, as well a dynamic flight model is also built to determine the...

The operation signal of an unmanned aerial vehicle's (UAV's) datalink will change with the flight radius and attitude, which leads to a dynamic variation of the electromagnetic susceptibility (EMS) of the datalink against the external electromagnetic interference. In order to predict the electromagnetic compatibility (EMC) for the dynamic datalink...

In this paper, the effect of the tilt angle of return stroke channel and the stratified lossy ground on the lightning-induced voltages on the overhead lines are studied using the MTLL model. The results show that the lightning-induced voltages from oblique discharge channel are larger than that from the vertical discharge channel, and the peak valu...

The analytic expressions of lightning electromagnetic fields generated by tortuous channel with an inclined lower section are obtained by decomposing the current infinitesimal and solving Maxwell's equations. By using the transmission line model and pulse function to express the channel-base current, the influence of length and tilt angle of t...

A kind of low-cost electric and magnetic field simulators, which are used to produce simulative lightning electromagnetic pulse (LEMP) with adjustable waveforms and intensity output, are presented. The lightning electric field can be produced within the GTEM cell by feed-in of impulse voltage output by a Marx generator. The lightning magnetic field...

In order to investigate the terminating load voltage of the unshielded multi-core cable coupled with lightning electromagnetic pulse(LEMP), we simulate LEMP within the bounded-wave transmission line which is input with a lightning surge signal produced by WU-800-type MARX generator and conduct the relevant experiments towards multi-core cable lines...

The waveforms of lightning return stroke electromagnetic fields on ground are studied using the transmission-line model. Approximate expressions to calculate lightning electromagnetic fields at near and far ranges are presented. It is found that, the waveforms of lightning electric and magnetic fields in the time domain at both near and far ranges...

A kind of electric and magnetic field generators with adjustable waveforms and intensity output to simulate lightning electromagnetic fields are presented. The electric fields measured by a dipole antenna and ranged from 0 to 300kV/m can be generated within the GTEM cell by feed-in of an impulse voltage. The magnetic fields measured by a 'B-dot' co...

In order to protect sensitive electronic components and electrical equipment against the influence of lightning electromagnetic pulse (LEMP) field in near area, it is necessary to determine the waveform of the lightning electromagnetic field. By using the dipole method to solve Maxwell's equations, the analytical expressions of lightning electromag...

A set of approximation expressions relating the lightning channel-base current and the lightning electric and magnetic fields on earth surface are proposed respectively in the near-zone and far-zone, by employing the transmission line (TL) model. The derived expressions show that, the electric and magnetic fields waveforms can be expressed approxim...

Unmanned Aerial Vehicle (UAV)data link system is the core part of the UAV system. In order to verify the safety and reliability of UAV in the ultra-wideband (UWB) electromagnetic pulse field environment, UWB electromagnetic pulse radiation system is set up in the open field. Using this system, experiments on irradiation effect for UAV data link sys...

In order to study the safety and reliability of Unmanned Aerial Vehicle in the battlefield electromagnetic environment, a continuous-wave electromagnetic radiating system is built in the laboratory. Using this system, experiments on irradiation effect for U AV data link system are implemented. Experimental results show that: the UAV data link syste...

The analytic expressions of the spatial lightning electromagnetic field are obtained by solving Maxwell's Equations based on the dipole method. On this basis, the waveforms of the electric and magnetic fields at different heights and distances in the near-zone are presented using the transmission line (TL) model and the channel-base current was des...

Based on the dipole technique, the exact expressions and approximate expressions for LEMP on earth surface are derived from the TL model and specified channel-base current described by a pulse function. According to the comparisons between the exact results and approximate results, the waveforms of LEMP and its derivative are similar to the lightni...

Monitoring of atmospheric electric field near ground plays a critical role in atmospheric environment detecting and lightning warning. Different environmental conditions (e.g. buildings, plants, weather, etc.) have different influences on the data's coherence in an atmospheric electric field detection network. In order to study the main influence f...

In order to make the calculation of lightning electromagnetic field closer to the actual status and simulate the lightning electromagnetic field in far zone, the analytical expressions of lightning electromagnetic field generated by oblique channel were derived with the dipole method, and the approximate relationships of lightning electromagnetic f...

Numerical simulation of lightning discharge is one of the most important methods to reflect the law of lightning progressing process and lightning strike incidence. In order to improve the spatial resolution of numerical simulation, combining the improved dielectric breakdown model with the boundary conditions of the calculation region, we proposed...

Choice of the return-stroke parameters has a great influence on the calculation results of lightning electromagnetic pulse(LEMP) fields. In this paper, LEMP fields under different return-stroke parameters are calculated based on the MTLL model in which the channel-base current is described by a pulse function. And effect of different return-stroke...

To investigate the elecromagnetic environment effects of the amplitude modulation wave on radio fuze, the mixing theory and the output signal character of high frequency circuit are analyzed, and the problems of waveform modulate are resolved. The modulate waveform expression and the radio fuze radiation electromagnetic environment is established....

Vehicle engineering major includes mechanical engineering, structural engineering, transportation engineering, etc. This paper introduces problems of traditional vehicle engineering teaching. We should strengthen the base of discipline construction to increase students’ learning interest. At last, a method of training vehicle engineering innovative...

In order to improve the field uniformity in the work space of a reverberation chamber, the mechanism of the position of emission antenna affecting the field uniformity was analyzed, and the simulation model was constructed and analyzed with FEKO software based on the method of moments combining genetic algorithm(GA) with MOM was put forward to anal...

The mixing theory of autodyne dynatron and the output signal character of a high frequency circuit are studied. The mechanism of simulated Doppler signal amplitude modulation wave to radio fuze is discovered. A certain radio fuze is selected, the irradiation experiment of amplitude modulation wave to radio fuze is done, and the field intensity for...

To develop the evaluation methods of lightning protection system, the high resolution simulation of cloud-to-ground lightning leaders was done based on a 3-D dielectric breakdown model(DBM) in an analytic thunderstorm model, then an evaluation model was established near ground and the evaluation experiment was done. The space resolution is 50 m and...

The results by accurately calculating with dipole method show that the waveform of the derivative of the electric field and waveform of the derivative of approximate calculation are consistent within 50 meters; and the derivative of the waveform of the magnetic field and the derivative waveform of approximate calculation are consistent within 200 m...

This paper mainly aims at the lightning stroke models which is commonly used. According to the principle of model, this paper separates it into two parts to introduce, simultaneity expatiates the hypothesis, the applicability and the limit of the models; points out the common characteristics of the models and the basic requirements of setting up an...

This chapter presents a research on the radiation effects of fast rise time (FREMP) toward radio fuse. The radio fuses under test are composed of high-frequency module, low-frequency module, and detonation-executing circuit. Its main technical parameters include emitting frequency, demodulation DC voltage, working current, and ignition sensitivity....

This chapter presents a research on the security of electro-igniting device in long-term storage condition toward Electrostatic Discharge (ESD). JD-AA is a kind of typical electro-igniting device that ignites the medicament by electro-heating bridge. To evaluate the anti-electrostatic ability of rocket roundly, JD-AA is stored in standard condition...

This chapter presents a research on the security of electro-igniting device in long-term storage condition toward Electrostatic Discharge (ESD). JD-AA is a kind of typical electro-igniting device that ignites the medicament by electro-heating bridge. To evaluate the anti-electrostatic ability of rocket roundly, JD-AA is stored in standard condition...

This chapter presents a research on the radiation effects of fast rise time (FREMP) toward radio fuse. The radio fuses under test are composed of high-frequency module, low-frequency module, and detonation-executing circuit. Its main technical parameters include emitting frequency, demodulation DC voltage, working current, and ignition sensitivity....