This PDF file contains the front matter associated with SPIE Proceedings Volume 12589 including the Title Page, Copyright information, Table of Contents, and Conference Committee Page

The protection design and certification of civil aircraft electromagnetic environmental effects face challenges due to the application of new fuselage materials and new technologies of airborne electronic and electrical equipment. The relevant airworthiness requirements of electromagnetic environmental effects protection are studied, then the protection design requirements, certification basis, means of compliance and verification characteristics are given. The focus points are given from the perspective of certification, then possible problems are illustrated during the certification process through certification cases.

In the process of oilfield waterflood development, the rate of water injection is an important embodiment of water injection management level, which is an important parameter that not only reflects the formation capacity, but also reflects the production capacity of water injection equipment. Because of the influence of injection water quality, production environment, management level and other factors, the water injection flowmeter needs to be calibrated regularly to ensure the accuracy of measurement in the actual water injection process. In Huabei Oilfield, the flowmeters used in the production are removable for calibration, which has problems such as the difficulties when dismantling and mounting the flowmeters for calibration outside, easily being damaged in transit and low calibration efficiency. In order to solve above problems, a set of on-line calibration skid-mounted device for water injection flowmeter is developed, which realizes on-line calibration for water injection flowmeter and meets the actual demands of water injection flowmeter calibration in oil field.

In this paper, ZnO doped with Cu and Mn ions with different molar ratios were prepared by hydrothermal method at 200 ℃ for 24 hours. Zn_0.95-xMn_0.05Cu_xO powders with different doping ratios were synthesized. Zn_0.93Mn_0.05Cu_0.02O, Zn_0.89Mn_0.05Cu_0.06O, Zn_0.85Mn_0.05Cu_0.10O and Zn_0.80Mn_0.05Cu_0.15O powders were obtained. XRD tests showed that all four samples were incorporated Cu²⁺ and Mn²⁺ at Cu²⁺:Mn²⁺=6:5 (Zn _0.89Mn_0.05Cu_0.06O) powder CuO and Mn₃O₄ peak strength are the highest. The EDS spectra show that it contains Zn, Cu, and O elements. SEM shows that the crystal structure of the product obtained by different doping ratios is different, where there are both regular crystals with shapes similar to boxes and flocs, irregular flakes, and very compact tiny crystals, which can be seen at Cu²⁺:Mn²⁺=6:5.

Infrared detectors are widely used in night vision imaging, security inspection, medical testing, environmental monitoring and other fields. Infrared detectors based on two-dimensional materials have become a research hotspot. A photoconductive graphene infrared detector based on inverted fluorination is introduced in this paper. An inverted fluorination method is adopted to reduce the physical bombardment damage to graphene and reduce the difficulty of graphene fluorination regulation. The Raman spectrum mapping of fluorinated graphene is analyzed. The variation of graphene Raman spectrum and infrared response against fluorination time is investigated, clarifying the properties of fluorinated graphene suitable for infrared sensing. The graphene sensor shows the highest responsivity when the value of ID/ID' peak ratio of the graphene Raman spectrum is the lowest. The photoconductive graphene infrared sensor based on controllable inverted fluorination process has the advantages of simple structure, high process feasibility.

In recent years, rare earth doped optical materials have been widely used in w-LEDs, optical displays and lasers. Glass ceramics containing titanate crystal phases are widely used in the matrix of luminescent materials because of their high thermal and chemical stability, excellent luminescence properties, and low phonon energy. However, Y₂Ti₂O₇ with a pyrochlore structure is considered a good up-conversion luminescent matrix owing to its low phonon energy (⪅712 cm^-1). By the melt crystallization, Tb³⁺ doped transparent glass ceramics (GCs) were prepared. Y₂Ti₂O₇ crystal phase in glass ceramics was decided by using x-ray diffraction. The light transmittance of the glass ceramics can reach 71% in the visible region. The emission intensity is the strongest when the doping concentration of Tb³⁺ is 0.4%. Compared with the precursor glass, glass ceramics have higher luminescence intensity. It can be concluded that Tb³⁺ doped transparent glass ceramics containing Y₂Ti₂O₇ crystal can be used in green light emission fields.

With the continuous development of science and technology, glass ceramics containing phosphate crystal phases have the advantages of good network formation, low propagation loss, easy preparation, good optical stability, low phonon energy and high solubility of rare earth ions, while being well suited as light emitting materials for various optical devices. Sm³⁺ ions are commonly used as activating ions for orange-red light and are a suitable source for lighting and display devices. In this work, Sm³⁺ doped glass ceramics containing Ba₃Gd(PO₄)₃ crystal phase have been prepared through melt crystallization method. Compared with the precursor glass sample, glass ceramics had higher luminescence intensity. Sm³⁺ doped glass ceramics containing Ba₃Gd(PO₄)₃ crystal phase had been a promising orange-red luminescent material with potential application in w-LEDs.

Sn-doped ZnO thin film was prepared to enhance its photoelectric performance, and the ZnO based photodetector was fabricated by co-sputtering method. The I-V characteristic of the detector under different Sn doped DC sputtering power, the ultraviolet light source was set at 365 nm with 0.5 mW power. The examined photodetector performance manifest that optimum Sn doping level is investigated at 15 W, the maximum photocurrent and spectral responsivity are obtained to be 4.39 mA and 24.4 A/W, the fastest time response is obtained to be t_r=29.0 ms and t_f =33.2 ms.

The semiconductor industry is developing rapidly, and a variety of semiconductor materials have emerged. At present, silicon and gallium nitride, which play a leading role in semiconductor materials, play an important role in different fields. This paper summarizes the characteristics and social application of gallium nitride and silicon and compares them with those of gallium and silicon. Silicon has the characteristics of rich reserves, low price and mature development. Gallium nitride has the characteristics of wide band gap, thermal stability, high frequency, high electron mobility and high power. This study enriches the comparative theory of silicon and gallium nitride. In the process of developing global informatization and economic globalization, it is very important to dig deep into the traditional properties and characteristics of silicon and explore the cutting-edge technology of gallium nitride.

In order to realize the miniaturized application of the Fiber Optic Gyroscope (FOG), combined with the characteristics of the drive circuit, the MIOC (Multifunctional Integrated Optical Circuit) drive circuit is simplified and designed, and only the single-chip operational amplifier is used to realize the differential current conversion of the DAC output to the drive voltage and the amplification function. Through simulation and circuit board experiment verification, the improved circuit design meets the driving requirements of MIOC and achieves an effective amplification of nearly ten times the output differential current signal of the DAC. The circuit design has been applied in the miniaturized fiber optic gyroscope of our company, and it has become a practical and reliable driving circuit design scheme.

We numerically demonstrate a broadband single polarization Photonic Crystal Fiber (PCF) based on surface plasmon resonance effect. The PCF is constructed of multi-layer hexagonal air holes with a silicon core. The inner wall of the two large air holes is coated with gold films for exciting surface plasmon resonances. The transmission characteristics of the fiber are analyzed by the finite-element method. At the wavelength point of 1.55 μm, the confinement losses of the x and y-polarization modes are 1400 dB/m and 15 dB/m, respectively. The severe difference in polarization loss can support the efficient transmission of the y-polarization mode over the range of 1.51-2.24 μm. Only short fiber lengths of 2 cm, the achievable power of the y-polarization mode can be more than 0.5, and the extinction ratio is less than -20dB for the wavelength range. The presented fiber has promising application prospects in polarization-maintaining and high-power laser systems.

Optical Fiber Connectors (OFCs) have become widely used in a variety of fields as optical fiber communication technology has developed. Compared with the other working environment of the OFCs, the working environment in the airplanes is more complex and harsher, which leads to an increase in connector failure rate and failure impact. In this paper, based on the analysis of the influence of vibration, high-low temperature cycle, and oceanic atmosphere in the aircraft working environment on the physical parameters of OFCs, the effects of the complex environment in the airplane service on insertion loss of OFCs is studied and discussed.

Microscale or nanoscale patterns with specific structures on sapphire substrate can effectively reduce the dislocation defects of gallium nitride (GaN) material and improve the quality of gallium nitride crystal during the epitaxy growth of GaN-based light-emitting diodes, thus improving the internal quantum efficiency of LED luminescence. Numbers of methods have been used to fabricated patterned sapphire substrate. But most methods remain on the micron scale. In this work, the nickel annealing technique was introduced to fabricate a novel sapphire substrate, Hierarchical Patterned Sapphire Substrate (HPSS), which has typical characteristics of nano sapphire pillars on a Micro-Patterned Sapphire Substrate (MPSS) used for GaN-based Light-Emitting Diodes (LEDs). Nano-pillars with an average feature size of about 110 nm and feature surface density of ⪆2.339×10⁹ cm^-2 were obtained on commercial MPSS through this method. This nickel annealing technique provides an extremely simple, cost-effective and universal method to fabricate hierarchical patterns with two-inch wafer-scale. What’s more, the substrates can be not only sapphire but also extended to silicon, quartz and other heat-resisting materials which are widely used in photoelectric devices and micro/nanofabrication, making it a promising method to fabricate patterned substrate for industrial applications.

Laser is widely used in manufacturing, information transmission, biotechnology and other fields, but these fields often need the input beam with specific intensity distribution, and the Gaussian beam needs beam shaping to achieve the required illuminance distribution. Annular flattened beam has great demand in satellite communication, laser high-speed welding and other fields. The existing beam shaping system needs to compensate off-axis aberration and chromatic aberration, and its design process and system structure are complex. In this paper, we propose a design method of coaxial reflection annular beam shaping system based on geometric optics principle. Through ray mapping method to establish a mapping relationship, through geometrical optics principle to derive the freeform surface equation. We constructed the beam shaping system of the double freeform mirror, which can realize the annular flattened beam with a uniformity of 96.35%. Compared with the existing beam shaping system, the coaxial double reflection system has fewer optical elements, more compact structure, less calculation of optical element structure, and avoids off-axis aberration and chromatic aberration under the condition of similar shaping uniformity.

In order to prepare a novel cave-like bifunctional chelating agent for homogeneous phase time-resolved fluorescence immunoassay, using 2-benzyl oxo carbonyl 6-tert-butyl oxo carbonyl. The intermediate, 5-amino-(2-aminoethyl)-H(2,2)- aminotert-butyl ester E-14, was synthesized by five steps of reduction, oxidation, amination and hydrogenation of -L-lysine E-7. The synthesis methods and conditions of the first steps were mainly studied, and the molecular structure was analyzed by means of Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectrometer (FTIR), Mass Spectrometry (MS). It provides a valuable intermediate and preparation method for the application of homogeneous time resolved fluorescence immunoassay.

Oceans and rivers contain abundant renewable low-velocity flow energy without large-scale utilization. Here, we present a novel energy harvester based on vortex resonance to collect the low-velocity flow energy. The harvester is mainly constituted by a cantilever beam, a hollow cylinder, a carrier sheet, and a Solid-Liquid Triboelectric Nanogenerator (SLTENG). Computational fluid dynamic (CFD) and finite element analysis are used to simulate the vortex shedding frequency and the natural frequency of the harvester. After optimization of the structure, the natural frequency is close to the vortex shedding frequency (2 Hz) and reaches resonance. Furthermore, the state of the liquid inside the cylinder is analyzed by CFD under different volumes and diameters of the cylinder.

The main purpose of this paper was to design a novel structure mesoporous carbon composite materials and develop economic and green photocatalytic oxidation process for common chemical reaction intermediates of styrene oxide under ambient condition based on the basic principle of environmentally friendly chemistry. Order mesoporous silica was prepared by conventional hydrothermal method using triblock copolymer as template agent, and then order mesoporous carbon materials were synthesized via a simple template method by adding sucrose to the sulfuric-acid-treated mesoporous silica and followed by carbonization and removal template of mesoporous silica on account of inverse replica effects. The composite mesoporous carbon materials assembled in situ anatase TiO₂ of different contents were obtained through impregnation and sintering at 700℃ for 2h in nitrogen atmosphere for both removal of unhydrolyzed tetrabutyl titanate and crystallization of titanium dioxide. All the composite catalysts had been unambiguously characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscoscopy, scanning electron microscopy, and high-resolution transmission electron microscopy, etc. Structural and morphological of prepared carbon materials showed that the typical ordered mesoporous structure was maintained after TiO₂ insertion and active component of TiO₂ was uniformly distributed in mesoporous carbon channels. A variety of reaction parameters such as molar ration of H₂O₂ to the styrene, reaction time, solvent, the amount of catalyst and so on were optimized at length for epoxidation of styrene with H₂O₂ as the oxidant over prepared composite catalysts under photo-irradiation. The results indicated that reaction conversion reached over 30% with 90% selectivity under the photocatalytic condition for room temperature, 0.50g of styrene, 2.00g of H₂O₂(30%wt%), 0.200g of catalyst and 3h reaction time. This process strategy for green photocatalytic oxidation under ambient condition was expected to be applied to other organic synthesis processes as a general environmentally benign chemical means.

In order to mitigate the adverse effects of cathode gas pressure fluctuations on the lifetime of a Proton Exchange Membrane Fuel Cell (PEMFC), a model of a cathode supply system with a bypass valve structure was developed, and a pressure cooperative control strategy was established based on this structure. Bench tests have verified that the proposed structure and control strategy has a good control effect on the sudden pressure change. Pressure fluctuations can be controlled to around 50Pa under the step conditions used in the test, and the absolute value of the pressure inside the pipeline can be controlled to the preset target, which helps to improve the life of the stack.

The flowmeter uses the TDC-GP22 chip as the acoustic wave processing core, uses the TDC-GP22 module to generate pulse waves, and sends them to the corresponding ultrasonic signal drive circuit to improve the amplitude of the ultrasonic signal. The echo is sent to TDC-GP22 to calculate the forward and reverse time difference; the main control module selects the STM32F407 chip, controls the TDC-GP22 module to transmit forward and reverse ultrasonic signals, enters the signal drive circuit to receive the echo signal and loads it into the TDC -GP22 chip calculates the time difference, and finally sends the corresponding time difference data to the main control module, which is connected to the PC through the serial port to display the measured data; the test is carried out in the fluid circulation device in the laboratory, and the speed of the screw pump is controlled to adjust the pipeline. The mass flowmeter is used as the calibration instrument, and the final test results demonstrate that the measurement accuracy of the ultrasonic flowmeter meets the requirements of oilfield use.

Due to the high reversibility of the aluminum deposition/dissolution process, aluminum chloride-based room temperature molten salts exhibit excellent electrochemical performance as the electrolytes of rechargeable aluminum-ion batteries. Aluminum chloride-1-ethyl-3-methylimidazole chloride (AlCl₃-EMImCl), AlCl3-acetamide and AlCl₃-urea systems are considered as the ideal electrolytes for aluminum-graphite batteries. To better develop and apply those electrolytes, the effects of three electrolytes on the electrochemical performance of aluminum-graphite batteries were studied, comprehensively. AlCl₃-EMImCl electrolyte exhibits excellent rate capability and coulombic efficiency. While the AlCl₃-amide systems only provide one-third capacity of AlCl₃-EMImCl, and the coulombic efficiency is only about 90% at lower rates. The significant difference between the electrochemical properties of AlCl3-based electrolytes is related to the kinetics of ion transport and diffusion between the interface of electrolyte and cathode.

The solid-state method first prepared a series of Ca₃TeO₆:Tm³⁺ blue-emitting phosphors. The X-ray powder diffraction were used to analyze the phase formations and purity of Ca₃TeO₆:xTm³⁺, xNa⁺ (0.002 ≤ x ≤ 0.10). The detection wavelength (λem = 454 nm) and a excitation wavenlenth (λex = 359 nm) were used to study photoluminescence spectra. After the comparison of different concentration phosphors, the optimal doping one was found as 0.05. Electric multipole interaction was proposed as the mechanism for concentration quenching in Ca₃TeO₆ materials. Furthermore, the Ca₃TeO₆:0.05Tm³⁺ fluoresces blue with color coordinates (0.161, 0.0671). Based on these results, Ca₃TeO₆:Tm³⁺ phosphors could be promising blue-emitting materials for the white light-emitting diodes (w-LED) applications.

Tm³⁺ doped NaCa₃Bi(PO₄)₃F blue-emitting phosphors have been synthesized following a conventional high-temperature solid-state reaction. Their phase purity, optical characteristics were systematically studied. The results show that the optimal doping concentration of Tm³⁺was 0.05. Electric multipole interaction was proposed as the mechanism for concentration quenching in NaCa₃Bi(PO₄)₃F materials. Furthermore, the NaCa₃Bi(PO₄)₃F:0.05Tm³⁺ fluoresces blue with color coordinates (0.1592, 0.0346). The results indicated that NaCa₃Bi(PO₄)₃F:Tm³⁺ phosphors could participate in fabricating the w-LEDs as the blue component.

In recent years, the use of Ti-6Al-4V alloy in the aviation industry has been increasing. However, due to the difficult machining characteristics of Ti-6Al-4V, hole-drilling in titanium is a major problem plaguing the aviation manufacturing industry. Ultrasonic vibration-assisted machining is a special machining method with excellent advantages such as reduced cutting force and cutting temperature in drilling. To evaluate the distinction, this study attempts to establish a 3D finite element milling simulation model. The differences between Conventional Helical Milling (CHM) and Longitudinal-Torsional Ultrasonic Helical Milling (LTUHM) are compared in the simulation results. The results show that the cutting force and von Mises stress concentration can be effectively reduced in LTUHM, and the chip morphology is fragmentized in CHM while the chip is continuous in LTUHM.

In this paper, a multi-objective optimization model for the processing cost, quality loss and tolerance cost sensitivity of RV reducer’s cycloid-pin gear pair is constructed. The tolerance range is constrained based on the accuracy requirement and the actual machining capacity, and the design requirements of the gear pair clearance and allowable backlash are considered comprehensively. The tolerance optimization design of cycloid-pin gear pair is carried out by using NSGA-Ⅱ algorithm. The effectiveness and feasibility of tolerance optimization design are verified by comparing and analyzing the results before and after optimization.

When imaging long-range targets using ground-based optical systems, the presence of atmospheric turbulence can cause blurring, dithering, and other degradations in the observed images. In previous research work, the research objects are mostly point targets, and the research work on the recovery of extended targets is yet to be perfected. With the rapid development of deep learning, neural networks driven by data can be used to obtain the recovered images directly by establishing a nonlinear mapping relationship between the degraded and original images. Therefore, the use of wavefront phase detection devices can be avoided by deep learning algorithms. The neural network directly reconstructs the original target of the turbulent degraded image that solves the problem of image blurring due to dynamic turbulence. In this paper, we propose DeblurNet, which employs the global self-attentive module. It improves channel and spatial information extraction, reduces information loss between network layers and global interaction representation to improve the performance of deep neural networks. DeblurNet is used to minimize the effect of turbulence on images and is validated on the NWPU-RESISC45 dataset. We refer to two image evaluation criteria, PSNR and SSIM. From the results, the direct reconstruction of the original target image by deep learning has a good recovery effect.

Stable operation of underwater systems is critical to economic development. However, the system is exposed to certain security risks during the long working cycle due to the complex underwater environment. Therefore, real-time dynamic monitoring of these systems is even more important. We are committed to responding to external disturbances in a timely manner and minimizing damage. In addition, we should exclude the disturbance from the water waves when monitoring, which also increases the difficulty of determining the disturbance for underwater monitoring. This paper designs an underwater monitoring system based on phase-sensitive optical time-domain reflectometer distributed fiber-optic sensor, which can make more accurate judgment of underwater disturbance. At the same time, it has the advantages of enough monitoring range, long-term working ability and large frequency response.

Optical amplifiers are a crucial component for optical communication by maintaining the strength of optic signals over long distances. Currently, optic signals are usually amplified by Erbium-Doped Fiber Amplifiers (EDFA). Optical amplification with EDFAs utilize 20-30 meters of Erbium-doped optic fiber, which takes up a large volume. The large volume renders the integration of optical transmitters, optical receivers and optical network units difficult. Therefore, to make optical communication more convenient, research on reducing the size of optical amplifiers is important. This paper proposes the adding of silver nanowires onto Erbium-doped glass to enhance its luminous intensity, then verifies it through experiments. A layer of silver nanowires is plated over pieces of Erbium-doped glass. The excitation emission intensity of both the plated and un-plated Erbium-doped glass were tested. Through analyzing the excitation spectrum, I concluded that the layer of silver nanowires results in an increase in optical gain of the Erbium-doped glass of around 30%.

Due to the absorption and scattering of light by water medium and suspended particles, underwater images come with color deviation and blurred details. For different light absorption in different underwater environments, an adaptive compensation method for local color channels is proposed to enhance the compensation for severe attenuation areas, which is suitable for underwater scenes with multiple color deviations. The dark channel prior is used to remove the detail blurring caused by scattering, the multi-scale Gaussian convolution and gamma correction are adopted to estimate the local light, and the tolerance parameter is used to increase the transmittance of bright areas to compensate for the dark channel prior conditions. The enhanced image quality is evaluated by Underwater Image Quality Measurement (UIQM), Average Gradient (AG), and entropy. Experimental data show that the method improves the color deviation of underwater images in different environments, enhances color information, and improves the contrast of images.

As an n-type wide band gap nanomaterial (2.7-2.9 eV), In₂O₃ has an important application in gas sensing, light-emitting diodes, semiconductor lasers, medical imaging and other fields. Research shows that the luminous efficiency of In₂O₃ can be improved through rare earth doping. Eu³⁺, Er³⁺ doping has been widely studied, but there is no relevant explanation for the transition mechanism. In this paper, the formation energy of Eu³⁺ doped in different site as a functional of temperature and electronic properties was calculated by using first principal calculations. The result showed that under O-rich conditions, the formation energy is negative below 500 K regardless of the doping site, which proves that rare earth atoms below 500 K are very easy to be doped, especially Eu³⁺ at the In1(3) (or In1) site and the Eu³⁺ doped decrease the band gap. Then the best synthesis conditions are found to determine the doping site, which provides a theoretical basis for the experiment. At the same time, considering the experimental conditions oxygen vacancy (VO) also exist, we calculated the band structure of the In₂O₃ with VO and Eu³⁺ doped. It provides a basis for in-depth analysis of the function of impurity energy levels formed after rare earth element doping in the experiment from the matrix to the luminous center.

Optical communication systems based on Orbital Angular Momentum (OAM) theoretically have great potential to increase the channel capacity of the system. When light passes through a high scattering medium, its phase and intensity are affected by scattering, which makes it difficult to demultiplex the OAM modes. In order to alleviate the mode crosstalk caused by scattering, this paper proposes a deep learning-based scheme for OAM modes demultiplexing. A simulation model of the optical communication system is built based on the scattering medium transmission matrix theory. The multiplexed OAM beam is transmitted through the system to generate the speckle pattern, matching the incident phase distribution as the data set. Based on this dataset, a U-Net type Deep Neural Networks (DNN) are trained to reconstruct the phase of the light distorted by the scattering medium, thereby the multiplexed OAM modes are identified by a Visual Geometry Group (VGG) type DNN. The simulation results show that at a Signal-to-Noise Ratio (SNR) of (1, 20) dB, the recognition rate of the demultiplexed OAM modes can reach beyond 97%. For grayscale image transmitting via OAM multiplexing under the high scattering, the Pearson correlation between the demultiplexed image and the original image is more than 0.98.

Quaternary alloy Al₈Cu₃FePr was melted in the nonconsumable arc-furnace under an argon atmosphere. The microstructure of the alloy was observed and analyzed by scanning electron microscope after high temperature annealing. It indicates that the alloy is a single-phase alloy with uniform chemical composition. Then, the crystal structure of Al₈Cu₃FePr alloy was determined by powder x-ray diffraction technology. The results show that Al₈Cu₃FePr is isostructural with Al₈Cu₄Pr crystallizes in the Mn₁₂Th-type structure, lattice parameters a = 8.8299(1) Å, c = 5.1582(1) Å, unit-cell volume V = 402.18 ų , formula units per unit cell z = 2, calculated density ρ_x = 4.981 g/cm³ , F₃₀ = 122.6(0.006, 46), the space group I4/mmm(No.139), and the reference intensity ratio value obtained experimentally is 1.20.

Conventional cable joint fault detection methods use covariance matrices to extract fault features with high sample transformation amplitudes, resulting in significant differences between the obtained Wigner-Hough transformation peaks and the actual ones. Therefore, a new cable joint fault detection method is required based on the extended time-frequency domain reflection method. Based on the energy transfer characteristics of the cable, a transmission line schematic is drawn to extract the fault characteristics. Then the fault frequency domain is divided by combining the extended time frequency domain reflection to achieve cable joint fault detection. The experimental results show that the peak values of Wigner-Hough transitions obtained by the designed cable joint fault detection method are less different from the actual ones, which proves that its fault detection effect is good, accurate, and has a certain application value.

To address the problem that the conventional algorithm has a very high complexity in estimating the Direction of Arrival (DOA) of coherent sources in the background of color noise, this paper proposes a low-complexity DOA estimation method based on the fourth order cumulant and Toeplitz matrix reconstruction. Firstly, a Fourth Order Cumulant (FOC) matrix is constructed from the received signal vector to suppress the noise component, and the redundant information in the FOC matrix is removed by storing the matrix to obtain the reduced dimensional FOC matrix. Afterwards, the Toeplitz matrix is reconstructed to extend the array aperture and to achieve decoherence. Finally, the DOA estimation of the reconstructed matrix is performed using the MUSIC algorithm. Simulations demonstrate that the DOA estimation of coherent signals in a color-noise background is less complex and maintains a higher accuracy than conventional algorithms.

The challenge of detecting the infrared small target in complex scenes is how to enhance the target area and suppress the interference of the background and noise. We present an infrared small target detection method based on saliency and difference of Gaussian. By calculating the spectral residuals of the original infrared images to obtain the saliency map, and a gray difference map is computed by adopting the difference of Gaussian. By normalizing and fusing these maps, the final feature response map is obtained, which can restrain the background noise and enhance the targets. Finally, the adaptive threshold segmentation method is used to detect small targets from the feature response map. Experimental result indicates that the proposed method achieves better image processing effect than traditional detection algorithm, works well under the interference of background and noise as well as detects the target accurately under different complex backgrounds.

Magnetorheological Elastomers (MREs) are a new type of intelligent magnetically controlled material consisting of a polymer matrix and magnetic particles. The modulus of elasticity of MREs varies with the external magnetic field strength due to the electromagnetic stress between the internal magnetic particle. However, the weak magnet-oenological effect of MREs limits their development. In order to improve the performance of the MREs, a two-dimensional model of MREs is developed based on the equivalent volume cell method, and the force-magnetic coupling analysis is carried out with COMSOL. In this paper, the effects of volume fraction, particle distribution, and magnetic field strength on the magnetostatic shear mechanical properties of MREs were investigated. The results show that: the stress distribution inside of MREs is mainly concentrated on the particles and the contact position between the particles and air. Increasing the magnetic field and the magnetic particle content can effectively improve the magneto-mechanical properties of MREs. Increasing the magnetic field from 0.5T to 1.7T, the magnetic shear modulus was increased by 8.81%. Increasing the particle volume fraction from 15% to 60%, the magnetic shear modulus was increased by 313.64%. Decreasing the particle distance in the chain contribute to the magneto-mechanical properties enhancement.

The self-curing mechanism of water-base self-curing sand-casting coating is described. The relationship between the moisture content and the self-curing time of the coating is analyzed on the basis of the principle of non-isometric ball stacking and verified experimentally. The influence law and cause of the size-distribution and morphology of refractory-aggregate particle on self-curing time of coating is studied based on experiments. The results show that: the moisture content of the coating has an approximate linear relationship with the self-curing time of the coating, the particle-size distribution of refractory-aggregate has a significant effect on the self-curing time, while the particle size has little effect. The particle size of refractory aggregate should be normally distributed with an average particle size of 200 mesh to 325 mesh. The particle morphology of the refractory aggregate also significantly affects self-curing time of the coating, the coating prepared by the powder quartz whose grain shape is similar to the spherical shape has a low moisture content and the coating can cure quickly. The coating with a thickness of 0.5mm can achieve self-curing within 100 minutes under an environmental condition of a relative humidity of 80%±2%, which is expected to meet the production requirements of resin sand casting under high humidity climate conditions in South China.

Using the method of combining simulation analysis and experimental test, research on the control of the effluent flow under different water pressures of a constant-flow water saver was carried out. A study of the impact of traffic. The established gas-liquid two-phase flow-liquid CFD transient analysis process based on the UDF program has an error of less than 5% with the test results, which can provide directions for the design improvement and optimization of the constant-flow water saver. In order to improve the calculation efficiency, the corresponding steady-state analysis process is studied. The results show that, compared with the transient analysis process, the accuracy of the steady-state analysis process is over 95%, and the calculation efficiency can be doubled.

With the development of domestic commercial passenger aircraft, the performance requirements and integration level of the aircraft ram air system have gradually increased. In this paper, the modular integrated design of the air-conditioning secondary, primary heat exchanger, auxiliary cooling heat exchanger, air quasi-secondary, and primary heat exchanger in the system is carried out to obtain a new integrated form of heat exchanger. The CFD mathematical model of the corresponding ram air system and the Simulink simulation platform, a single-channel test bench is built to verify the effectiveness of the CFD mathematical model and the Simulink simulation platform, and the flow distribution and performance of the corresponding ram air system under different flight conditions are calculated.

Porous carbon with high specific surface and excellent conductivity has attracted more and more attention for supercapacitor application. Biomass-based carbon materials with low cost and abundant resources are widely used to prepare porous carbon. In this work, pectin and melamine are used as precursors, Ni²⁺ and Co²⁺ are used as doped metals sources. The porous carbon spheres with Ni/Co codoped are prepared through a hydrothermal method at 120℃ and are carbonized under N₂ atmosphere at 900℃. The obtained materials exhibited an excellent capacity of 312 F. g⁻¹ at 1 A. g⁻¹ with a good stability for a long time test.

The permanent magnet motor mainly uses the permanent magnet excitation, the motor fault will affect the excitation performance of the permanent magnet, thus affecting the performance of the entire motor, serious stator inter-turn short circuit fault will cause short circuit between phases, causing three-phase current imbalance, resulting in increased harmonic magnetic field, rotor temperature rise. In this paper, the 5kW permanent magnet synchronous motor in 200mm shaftless rimless thruster is taken as the research object, and the single-phase two-slot inter-turn short circuit and two-phase inter-turn short circuit are analyzed. The Ansoft finite element analysis software is used to analyze the influence on the motor by setting two kinds of winding faults, which provides a reference for the fault diagnosis of synchronous motor.

Islanding detection is a necessary function of photovoltaic microgrid system. When islanding occurs, it is required to quickly detect the islanding state, cut off the islanding power at the same time, and minimize the loss of microgrid. In view of the low detection efficiency of the traditional active frequency offset method in the islanding detection of inverter, a positive feedback active frequency offset method is proposed in this paper. This method perturbs the frequency from both positive and negative directions, which effectively solves the problem of low detection efficiency. The simulation results further verify the effectiveness of this method: it can not only quickly detect the island state and shorten the detection time, but also further reduce the blind area of island detection and improve the efficiency of island detection.

Photovoltaic power generation has the characteristics of intermittency and randomness, and its output power has strong volatility, which will endanger the stable operation of the power grid when connected to the grid. Using energy storage can reduce the volatility of photovoltaic grid connected power and realize the stabilization of the fluctuation of photovoltaic grid connected power. This paper analyses the requirements of the grid connected power fluctuation rate of the coupling energy storage device of the photovoltaic power generation system and uses the variation modal decomposition to decompose the original photovoltaic power to obtain the grid connected power that meets the fluctuation requirements. An over calculation example verifies that the photovoltaic power can reduce the power fluctuation after being compensated by the hybrid energy storage system and compares and analyses the configuration results of different energy storage schemes, verifying that the method proposed in this paper can reduce the power of energy storage capacity and annual comprehensive cost to improve the economy of the system.

Aiming at the problems of uneven illumination, detail loss and color distortion of video images caused by low illumination and contrast of mine environment, a mine image enhancement algorithm based on bilateral filtering function is proposed. The algorithm first converts the image from RGB space to HSV space to avoid destroying the color space, extracts the illuminance layer and reflection layer of the image according to the classical Retinex theory combined with bilateral filtering with edge retention, adaptively adjusts the lighting by gamma function, and uses the CLAHE algorithm to enhance the overall contrast. Experimental results show that the proposed algorithm is superior to other commonly used algorithms in terms of visual effects, information entropy, average gradient, standard deviation, etc., which effectively improves the overall brightness and contrast of the image and improves the problems of detail loss and color distortion and realizes the effective enhancement of mine images.