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The extraction of high-temperature regions in active regions is an important means to help understand the mechanism of coronal heating. The important observational means of high-temperature radiation in active regions is the main emission line of Fe xviii in the 94 ̊A of the AIA. However, the diagnostic algorithms for Fe xviii , including the DEM and linear diagnostics proposed by Del based on the DEM, have been greatly limited for a long time, and the results obtained are different from the predictions. In this paper, we use the outlier detection method to establish the nonlinear correlation between 94 ̊A and 171 ̊A, 193 ̊A, 211 ̊A based on the former researches by others. A neural network based on 171 ̊A, 193 ̊A, 211 ̊A is constructed to replace the low-temperature emission lines in the active regions of the 94 ̊A. The predicted results are regarded as the low-temperature components of 94 ̊A, and then the predicted results are subtracted from 94 ̊A to obtain the outlier component of 94 ̊A, or Fe xviii. Then, the outlier components obtained by neural network are compared with the Fe xviii obtained by DEM and Del’s method, and a high similarity is found, which proves the reliability of neural network to obtain the high-temperature components of active regions, but there are still many differences. In order to analyze the differences between the Fe xviii obtained by the three methods, we subtract the Fe xviii obtained by the DEM and Del’s method from the Fe xviii obtained by the neural network to obtain the residual value, and compare it with the results of Fe xiv in the temperature range of 6.1-6.45 MK. It is found that there is a great similarity, which also shows that the Fe xviii obtained by DEM and Del’s method still has a large low-temperature component dominated by Fe xiv, and the Fe xviii obtained by neural network is relatively pure.

Extrinsic Calibration between LiDAR and POS (position and orientation system) is a fundamental prerequisite for varieties of MLS (mobile laser scanner) applications. Due to the sparse structure of LiDAR data, the current calibration methods relying on common point feature matching are unreliable, and the low accuracy POS results make the extrinsic calibration of MLS system more challenging. In this paper, we propose an incremental estimation method of six degree of freedom extrinsic transformation of LiDAR and POS. Firstly, the POS-SLAM is used to accumulate LiDAR scans as online sub maps. Attitudes of the carrier are calculated by using GNSS/INS loose combination method of bidirectional adjustment, and scans are associated with sub map based on the time interpolation. Then, the extrinsic calibration parameters are estimated by optimizing corresponding points difference between SLAM and MLS coordinate frame. Finally, field tests have been conducted to the proposed method. RMS between the map by the calibrated MLS and by the static measurement is 0.57 cm. The results demonstrate that the accuracy and robustness of our calibration approach are sufficient for mapping requirement of MLS.

The microwave discharge cusped field thruster is a novel concept electric micro propulsion device, also a candidate thruster for the gravitational detection mission. A coaxial transmission line resonator is utilized to feed the microwave into the thruster to generate Xe plasma steadily with a mass flow rate as low as 0.1 sccm. Due to the separation of ionization and acceleration, the thruster performs high operation mode stability over a wide range of voltage in low mass flow conditions. Experimental and simulation methods are carried out to study the ionization and ion acceleration of the thruster. The results show that in operating conditions with a mass flow rate of 0.1 sccm, an anode voltage of 0 V to 1000 V, and a microwave power of 2 W, the right-hand circularly polarized wave (R wave) and the ordinary wave (O wave) play the most important role in the ionization process. The ion acceleration region locates around the exit magnetic separatrix, and the acceleration region tends to converge toward the separatrix as the anode voltage increases, resulting in an increased focus of the thruster plume and concentration of the ion energy distribution. Due to the separation of the ionization and acceleration regions, the thruster performs a divergence efficiency of 0.5–0.8, and an acceleration efficiency of 0.9.

Channel equalization is essential in wideband digital array radar to compensate the channel distortion and mismatch. Inverse Fourier transform (IFT) method and weighted least squares (WLS) algorithm are used to calculate the coefficients of the equalizer filter. However, the accuracy of equalizer coefficient calculation is affected by many non-ideal factors in the actual correction of large-scale digital TR channels. This paper aims to analyze the influence of various non-ideal factors in equalizer coefficient calculation and propose a test method to reduce or eliminate their influence. Finally, based on 90 channel scale FPGA-based system, the method proposed in this paper is tested and verified, and good performance is achieved.

As an ideal visual perception system with miniaturization, multi-aperture, wide field of view, low aberration, infinite depth of field, high efficiency and real-time, bionic compound eye has obvious intelligent characteristics, which provides a new idea for the future intelligent development of precision guided weapons, and has also been highly concerned by the US military. Under the leadership of the military, the United States has carried out a series of studies and achieved a series of results. The strategic position of urban combat in the future is analyzed. The requirements of the U.S. Air Force for the next generation of precision-guided munitions, and also the strategic significance of developing urban combat weapons and equipment is described. The advantages and characteristics of artificial compound eye are briefly described. Mainly discussed a series of WFOV artificial compound eye seeker being studied and developed by the U.S. Air Force for urban warfare, as well as the research and development process. Finally, the development suggestion of the WFOV artificial compound eye seeker is given.

Light-emitting diode (LED) is now the main type of light source in global lighting marketing. However, traditional photometry with the incandescent standard lamp is not sufficient to implement high-level LED photometric measurement, since a considerable spectral mismatch error may exist if the photometer has a large general V(λ) mismatch index f 1 ′ . The LED standard lamp is proposed to be the complementary transfer standard for photometry to reduce this measurement uncertainty. National Institute of Metrology, China (NIM) has previously reported a type of LED filament lamp for total luminous flux. In this article, NIM demonstrates another type of LED filament lamp for luminous intensity calibration. The LED filaments are sealed in a T90 cylinder glass bulb as emitters, and have a spectrum similar to the reference white LED spectrum considered in Commission on Illumination technical committee 2–90. The LED lamp uses the E27 screw base as the connector, and is compatible with the traditional alignment approaches. The warm-up time is less than 12 min. The output change of a group of 12 lamps, over nearly two years of storage and 1 h operation every day during the whole long-term test, is found to be ±0.2% or less for most of the lamps. The ageing effect of one lamp over a continuous 6500 h of burning is estimated to be −0.014% per 100 h, and it is significantly lower than 1% per 100 h, the typical drift rate of the traditional incandescent luminous intensity lamp. In the aspect of the coincidence with inverse square law, the LED lamp has a similar performance to the WI41/G lamp, the traditional luminous intensity lamp.

In this work, we have carried out a simulation study on the discharge process of Hall thrusters under the conditions of different neutral gas radial supply positions based on the particle-in-cell (PIC) and Monte Carlo collision (MCC) methods. This paper compares the two-dimensional (2D) distributions of neutral gas, plasma and wall erosion-related parameters under different neutral gas supply positions. The comparison results show that the change of the neutral gas supply position affects the radial distribution uniformity of the neutral gas and plasma in the channel. From the comparison of the density peaks, it can be found that the neutral gas density and the plasma density peak under the upper gas supply condition are relatively low, and the plasma density peak is 22.49% lower than the density peak under the middle gas supply condition. Meanwhile, as the radial position of the gas supply moves from the lower gas supply to the upper gas supply, the position of the ionization zone also gradually moves toward the anode. The results of erosion-related parameter distribution comparison show that the change of gas supply location has an obvious influence on erosion rate and erosion range. In terms of erosion rate, the wall erosion rate is relatively low under the upper gas supply condition, and the peak erosion rates of the inner and outer walls are 33.3% and 29.9% lower than those under the other two conditions. In terms of erosion range, as the gas supply position moves from the lower gas supply position to the upper gas supply position, the erosion range gradually increases from 5 to 7.5 mm.

Heavy mud pollution tends to occur during the workover of deep tight sandstone gas wells in Tarim, resulting in a significant reduction in gas well production. In order to study the impact of heavy mud pollution in deep sandstone gas reservoirs in the Tarim Basin, the physical properties and mechanical parameters of cores before and after heavy mud pollution were tested by non-destructive testing methods such as porosity, permeability, and acoustic waves. The results show that after the matrix core is polluted by heavy mud, the overall damage of permeability is ≥60%. Low-density mud causes more damage than high-density mud. The effect of increasing displacement time on permeability damage is higher than that of increasing displacement pressure. Heavy mud has an obvious influence on matrix porosity, but with the change in displacement pressure and displacement time, the change in core porosity has no obvious regularity. After the matrix core is polluted by heavy mud, the Poisson’s ratio increases by about 70% on average, but the change in elastic modulus is small, only -1.15%−4.25%. The experimental results provide significant guidance for reservoir damage assessment of mud-contaminated wells in Tarim.

A continuous wave (CW) Watt-level wavelength-variable low-noise all-solid-state yellow-green laser was developed by using the Brewster polarizer frequency selection and birefringent crystal filtering methods. The maximum CW output power of the yellow-green laser beams radiating at wavelengths of 556.32 nm, 558.36 nm and 561.63 nm was measured to be 2.922 W, 2.713 W and 2.514 W, respectively. When the CW output power was 2.5 W within 4 h, the power instability of the three yellow-green laser beams from the shortest wavelength to longest wavelength was ±0.55%, ±0.46%, and ±0.69%, respectively. Their corresponding laser noise was 0.65%, 0.48%, and 0.72%. To the best of our knowledge, the Watt-level wavelength-variable all-solid-state yellow-green laser with low noise proposed in this study is the first of its kind.

Here, we report the evolution of the physical properties of Eu-doped polycrystalline perovskite iridates Sr2-x Eu x IrO4 (x=0, 0.02, 0.04, 0.06). It is found that substituting Eu3+ for Sr2+ retains the I41/acd crystal structure but causes rotation of IrO6-octahedra decreases so that the bond angle of Ir-O1-Ir increases. The SEM micrographs indicate that the average grain size decreases, while the grain size distribution increases with doping. Compared with the resistivity of the parent material, all the doped materials show an increase, which can be further verified by the slight increase of band gap obtained from ultraviolet-visible absorption spectra. Furthermore, Eu doping makes the dielectric constant increases and thus the ability of electrical conduction decreases. All the physical properties of the compounds rely heavily on the parameters of their crystal structure, φ Oct and c/a, implying spin-lattice coupling makes an important contribution to the electric behaviors.

Sr2IrO4 is predicted to be a new superconductor in theory, and its electric transport properties have attracted much attention in the field of physics. Here we prepared a series of polycrystalline samples doped with Sr2-xBixIrO4 (x=0,0.02,0.04,0.06,0.08) and Sr2-yDyyIrO4 (y=0,0.02,0.04,0.06) respectively. The influence of the two ions on the lattice structure and electronic structure after the substitution of the Ir site is very similar, which makes the overall reduction trend of IrO6 octahedron and Ir-O1-Ir bond angle. The resistivity shows a non-monotonic change with doping and still maintains the insulation. The low-temperature section, medium-temperature section, and high-temperature section conform to three-dimensional variable range hopping (3D-VRH), thermal activation model, two-dimensional weak localization model respectively.

We investigate the effect of ozone (O3) oxidation of silicon carbide (SiC) on the flat-band voltage (V fb) stability of SiC metal–oxide–semiconductor (MOS) capacitors. The SiC MOS capacitors are produced by O3 oxidation, and their V fb stability under frequency variation, temperature variation, and bias temperature stress are evaluated. Secondary ion mass spectroscopy (SIMS), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) indicate that O3 oxidation can adjust the element distribution near SiC/SiO2 interface, improve SiC/SiO2 interface morphology, and inhibit the formation of near-interface defects, respectively. In addition, we elaborate the underlying mechanism through which O3 oxidation improves the V fb stability of SiC MOS capacitors by using the measurement results and O3 oxidation kinetics.

Taking the Tianma Radio Telescope (TMRT) as an object, this paper focuses on the determination of temperature gradients and thermal deformations of the backup structure (BUS) with the finite element method. To this end, a modeling and analysis method, which consists of a simplified FEM and a four-component simulation process, is proposed. In the development, only solar radiation is considered and thermal convection is neglected. Based on the thermal time constant of the BUS, the simulations of temperature gradients are simplified as static analysis. The superposed temperature gradients agree well with the ones measured by thermometers with a 0.57°C root mean square (rms) error. In addition, the illuminated-weighted rms errors of the primary reflector surface calculated by the simulation and measured by the extended out-of-focus holography are in good agreement. The rms error increases approximately 170 μm when the Sun persistently illuminated the BUS for 3 hr. The optimized initial temperature of the antenna structure is 20°C by comparing the results between the finite element analysis and the e-OOF measurement. The thermal deformation database can support the real-time compensation of the active surface system if the traces of the radio telescope are known in advance.

Many low Earth orbit (LEO) satellite constellations have been designed in recent years to provide global broadband Internet services. These constellations provide opportunities for LEO satellites to serve as navigation satellites by launching navigation signals while also being equipped with an onboard global navigation satellite system (GNSS) receiver. We propose a kinematic precise orbit determination (KPOD) and precise clock estimation (PCE) approach for LEO satellites by integrating regional ground observations and onboard observations of LEO satellites. By taking into account the LEO satellite clock bias, this approach can demonstrate the contributions of the ground and onboard observations of LEO satellites to the orbit and clock results, respectively. A composite LEO satellite constellation consisting of 168 satellites and observations from regional ground stations and LEO satellite onboard receivers are simulated considering the LEO satellite clock bias to verify the proposed approach. The results indicate that the convergence time of LEO satellite orbit determination can reach 9.38 min with the integrated KPOD (IKPOD) method, which is a reduction of 24.0% compared with the traditional KPOD method. However, the additional improvement in the LEO satellite orbit accuracy after convergence is very limited. The average root mean square (RMS) and standard deviation (STD) values of all LEO satellite clocks using the integrated PCE (IPCE) method with the participation of LEO satellite onboard observations can reach 0.27 ns and 0.15 ns, respectively. The improvements in the average RMS and STD are 42.6% and 60.5%, respectively, compared with the ground LEO PCE method. The convergence time and accuracy of LEO/GNSS precise point positioning can be improved by 44.6%, 48.3%, 26.7%, and 20.4% in the east, north, and up directions, respectively, using LEO satellite orbits and clocks from the IKPOD and IPCE methods compared with KPOD and PCE.

The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations. The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.

Hydrogel microbeads are promising matrices for cell-based meat culture because they can be conveniently fabricated from food-grade materials. In this study, food-grade sodium alginate was successfully applied to fabricate edible microbeads with the desired diameters (∼200 µm) using electrospray technology. Pure alginate microbeads have poor cytoaffinity. To enhance the cytoaffinity of alginate microbeads for meat culture, we applied different gelatin coatings, namely porcine gelatin, bovine gelatin, and fish gelatin, onto alginate beads. The modification is non-toxic and environmentally friendly with the use of plant-derived crosslinkers and under mild reaction conditions. As all ingredients are food grade, the modified microbeads are edible and biodegradable, with the mean diameters of 142.96 ± 35.49 μm (porcine gelatin-coated beads), 105.12 ± 80.46 μm (bovine gelatin-coated beads), and 94.81 ± 67.38 μm (bovine gelatin-coated beads). These modified microbeads have self-fluorescence and can be easily distinguished under a fluorescent microscope. The hydrogel core enables the microbeads to have a density of 1.04 g cm−3 for suspension culture. Bovine gelatin-coated microbeads have the best primary porcine myoblast and C2C12 cell adhesion, and can achieve between 16- to 18-fold proliferation of different muscle cells. With the successful differentiation of C2C12 and proliferation of 3T3-L1 adipocytes on bovine gelatin-coated microbeads, cells and microbeads can form clusters, illustrating that our edible microbeads are promising microcarriers for mammalian cell culture for cell-based meat production.

The New Vacuum Solar Telescope (NVST) has been releasing its novel winged Ha data (WHD) since April 2021, namely the Ha imaging spectroscopic data. Compared with the prior released version, the new data are further co-aligned among the off-band images and packaged into a standard solar physics community format. In this study, we illustrate the alignment algorithm used by the novel WHD, which is mainly based on the optical flow method to obtain the translation offset between the winged images. To quantitatively evaluate the alignment results of two images with different similarities, we calculate the alignment accuracies between the images of different off-band and line center, respectively. The result shows that our alignment algorithm could reach up to the accuracy of about 0.1 "when the off-band of winged image is lower than 0.6 \.A. In addition, we introduce the final product of the WHD in detail, which can provide convenience for the solar physicists to use high-resolution H{\alpha} imaging spectroscopic data of NVST., Comment: 11 pages, 5 figures

The first atmospheric window of 3–5 μm in the mid-infrared (MIR) spectral range pertains to crucial application fields, with particular scientific and technological importance. However, conventional narrow-bandgap semiconductors operating at this band, represented by mercury cadmium telluride and indium antimonide, suffer from limited specific detectivity at room temperature and hindered optoelectronic integration. In this study, a plasmonic hot electron-empowered MIR photodetector based on Al-doped ZnO (AZO)/bi-layer graphene heterostructure is demonstrated. Free electrons oscillate coherently in AZO disk arrays, resulting in strong localized surface plasmon resonance (LSPR) in the MIR region. The photoelectric conversion efficiency at 3–5 μm is significantly improved due to plasmon-induced hot-electron extraction and LSPR-enhanced light absorption. The specific detectivity reaches about 1.4 × 1011 Jones and responsivity is up to 4712.3 A/W at wavelength of 3 μm at room temperature. The device’s specific detectivity is among the highest performance of commercial state-of-the-art photodetectors and superior to most of the other 2D materials based photodetectors in the MIR region. These results demonstrate that a plasmonic heavily doped metal oxides/2D material heterostructure is a suitable architecture for constructing highly sensitive room-temperature MIR photodetectors.

A large amount of ultra-low-power consumption electronic devices are urgently needed in the new era of the internet of things, which demand relatively low frequency response. Here, atomic layer deposition has been utilized to fabricate the ion polarization dielectric of the LiPON–Al2O3 hybrid structure. The LiPON thin film is periodically stacked in the Al2O3 matrix. This hybrid structure presents a frequency-dependent dielectric constant, of which k is significantly higher than the aluminum oxide matrix from 1 kHz to 200 kHz in frequency. The increased dielectric constant is attributed to the lithium ions shifting locally upon the applied electrical field, which shows an additional polarization to the Al2O3 matrix. This work provides a new strategy with promising potential to engineers for the dielectric constant of the gate oxide and sheds light on the application of electrolyte/dielectric hybrid structure in a variety of devices from capacitors to transistors.

The uninhabited island in Guangdong is rich in vascular plant flora. In order to enrich the understanding of the zonal vegetation, a comprehensive survey of the plant resources of Sanzhou Island was carried out by using the survey method of the combination of sample line method and quadrat method. The vegetation types, floristic composition of vascular plants and the distribution types of families, genera and species were analyzed. The natural vegetation of Sanzhou Island could be divided into three types: coastal semi-mangrove, evergreen shrub and evergreen seasonal rainforest. The results showed that there were 68 species of vascular plants in 39 families, 62 genera. There were 4 families, 4 genera and 5 species of pteridophytes, accounting for 10.26%, 6.45% and 7.35% of the vascular plants; 63 species of angiosperms, 58 genera and 35 families, accounting for 89.74%, 93.55% and 92.65% of the vascular plants in the island. The floristic composition of the island showed obvious tropical nature. The main flora of the island was composed of 4 distribution types: pantropic, old world tropical, tropical Asia to tropical Australasia and tropical Asia. It showed the floristic components were diverse with strong adaptability which was suitable for the poor soil and harsh environment of the island. This study could provide a theoretical basis for the protection, development and management of plant resources in Sanzhou Island.

The β-Ga2O3 ultraviolet (UV) detectors work in the solar-blind (UV) band due to the ultra-wide bandgap of β-Ga2O3. In this paper, a solar-blind ultraviolet detector based on an ordered nanoporous β-Ga2O3 (ONP-β-Ga2O3) film is proposed and implemented. The local enhancement effect of the ordered nanopores on light is simulated by finite-difference time-domain method, and the period and diameter of the nanopores are optimized. Graphene is transferred on the ONP-β-Ga2O3 film and prepared as interdigital electrodes of the solar-blind ultraviolet detectors. The optimal detector has a photo-to-dark current ratio of about 4.64 × 103 at a 5 V bias, a peak response of 2.43 A W−1 at 254 nm, and a UV/visible rejection ratio of about 1081. We demonstrate that the ordered nanoporous structure can localize optical field effectively, which results in enhancement of light absorption as well as improvement of key detector parameters.

Recent investigations have derived the relation between the near-field plane amplitude and the surface deformation of reflector antenna, namely deformation-amplitude equation (DAE), which could be used as a mathematical foundation of antenna surface measurement if an effective numerical algorithm is employed. Traditional algorithms are hard to work directly due to the complex mathematical model. This paper presents a local approximation algorithm based on artificial neural network to solve DAE. The length factor method is used to construct a trial solution for the deformation, which ensures the final solution always satisfies the boundary conditions. To improve the algorithm efficiency, Adam optimizer is employed to train the network parameters. Combining the application of the data normalization method proposed in this paper and a step-based learning rate, a further optimized loss function could be converged quickly. The algorithm proposed in this paper could effectively solve partial differential equations without boundary conditions such as DAE, which at the same time contains the first-order and the second-order partial derivatives, and constant terms. Simulation results show that compared with the original algorithm by Fast Fourier transform, this algorithm is more stable and accurate, which is significant for the antenna measurement method based on DAE.

The target distance and test angle are the main factors that affect the accuracy of infrared temperature measurement. To study the infrared temperature measurement precision of different heat source intensities at different distances and test angles, a temperature measurement test with built-in heat source within the rod of the insulator was designed. By setting four different heat source temperatures on the heating film, the temperature data were collected by infrared camera at the distances of 3, 6, 9, 12 m and 15 m and three test angles of 0 °, 90° and 180°, respectively, and the variation law of the measurement results was analysed. The main conclusions are as follows. As the distance increases, the measured values basically show a downward trend. When the distance reaches 12 m, the temperature fluctuates significantly. When the angle between the observation direction and the heat source is 0 °, the measurement value is the highest, followed by the 90° direction, and the lowest is the 180° direction, which indicates that the test angle has an obvious influence on the measurement results. With the increase of heat source temperature, the infrared temperature measurement value increases gradually and tends to be saturated. When an infrared device is adopted to measure the temperature of the insulators in service, it is necessary to pay attention to the influence of the distance and angle on the value in engineering practice.

Infrared temperature measurement is an effective means for insulator health monitoring, and the theoretical basis and the subsequent diagnosis methods have been widely studied. However, in practical applications, the influence of insulator itself on fault temperature rise is rarely considered. In this paper, the temperature rise experiment of composite insulator was conducted to study the influence of sheath thickness and core rod diameter on fault temperature rise. According to the experimental results, the evolution law of fault temperature rise with the change of sheath thickness and core rod diameter was obtained. On this basis, the design strategy for composite insulators was proposed.

Composite insulators are affected by various factors in operation. With the increase of operation time, the shed of silicone rubber composite insulators will become hard and brittle. In this paper, it is found that the hardness of long-term silicone rubber shed meets the standard requirements. The tear strength, tensile strength, elongation at break, resistance to electric tracking and corrosion loss decrease significantly after 5-10 years of operation. The decline of silicone content on the micro surface and the escape of inorganic fillers are the reasons for the deterioration of macro performance. Finally, the evaluation system for aging performance of insulators is preliminarily established, according to the aging degree of insulator, operation and maintenance suggestions are proposed.

In recent years, there have been a number of composite insulator decay-like fracture faults characterized by resin degradation and irregular fracture morphology, which seriously threaten the safety and stability of power system. At present, the research of composite insulator’s decay-like fracture is still in the initial stage at home and abroad, and there is no clear conclusion on the causes of its fracture, influencing factors and other important scientific and technical issues, and there is no unified understanding of the mechanism of decay-like fracture. In view of the above problems, this paper carries out acid corrosion test on core rod samples to explore the corrosion law of nitric acid on core rod and its influence on properties. The results show that acid corrosion is one of the factors causing the degradation of epoxy resin. With the increase of nitric acid concentration and soaking time, the degradation rate of epoxy resin accelerates, and the core rod sample gradually changes from emerald green to yellowish brown, then to light yellow, and finally to white hair like glass fibre. The effect of the sample under the long-time action of low concentration nitric acid is the same as that under the short-time action of high concentration nitric acid. Nitric acid will continuously erode into the core rod, resulting in the decrease of hardness and performance on the core rod surface.

Within the frame of classical electrodynamics, nonlinear Thomson scattering by an electron of a tightly focused circularly polarized laser has been investigated. The electron motion and spatial radiation characteristics are studied numerically when the electron is initially stationary. The numerical analysis shows that the direction of the maximum radiation power is in linear with the initial phase of the laser pulse. Furthermore, we generalize the rule to the case of arbitrary beam waist, peak amplitude and pulse width. Then the radiation distribution is studied when the electron propagates in the opposite sense with respect to the laser pulse and the linear relationship still holds true. Last we pointed out the limitation of the single electron model in this paper.

Polyaniline, as a kind of conductive polymer with commercial application prospects, is still under researches in its synthesis and applications. In this work, polyaniline was fabricated on flexible substrates including carbon cloths and polyethylene naphthalate by in situ electropolymerization method. The synthesized flexible electrodes were characterized by scanning electron microscopy, High resolution transmission electron microscope, atomic force microscope, Fourier transform infrared, x-ray diffraction, and x-ray photoelectron spectroscopy. Owing to the conductivity and the reversible redox property, the polyaniline/carbon cloth electrodes show excellent properties such as decent supercapacitor performance and good detection capability toward ascorbic acid. As supercapacitors, the electrodes exhibit a specific capacitance as high as 776 F g–1 at a current density of 1 A g–1 and a long cycle life of 20 000 times in the three-electrode system. As ascorbic acid sensors, the flexible electrodes demonstrate stable response to ascorbic acid in the range of 1–3000 μM with an outstanding sensitivity (4228 μA mM–1 cm–2), low detection limit (1 μM), and a fast response time. This work holds promise for high-performance and low-cost flexible electrodes for both supercapacitors and non-enzymatic ascorbic acid sensors, and may inspire inventions of self-powered electrochemical sensor.

Objective.For certain radionuclides that decay through emitting two or more gamma photons consecutively within a short time interval-called cascade gamma-rays, the location where a radiopharmaceutical molecule emits cascade gamma-rays can be identified through coincidence detection of the photons. If each cascade photon is detected through a collimation mechanism, the location of the molecule can be inferred from the intersection of the back-projections of the two photons.Approach.In this work, we report the design and evaluation of a three-dimensional stationary imager based on this concept for imaging distributions of cascade-emitting radionuclides in radiopharmaceutical therapy. The imager was composed of two gamma-ray cameras assembled in an L-shape. Both cameras were NaI(Tl) scintillator based, one with a multi-slit collimator, the other with a multi-pinhole collimator. The field of view (FOV) was 100 mm (∅) × 100 mm (L). Based on the unique characteristics of the cascade coincidence events, we used a direct back-projection algorithm to reconstruct point source images for assessing the imager's intrinsic spatial resolution and the standard maximum likelihood expectation maximization algorithm for reconstructing phantom images.Main results.We evaluated the performance of the imager in both simulated and prototype form with radionuclide177Lu (cascade photon emitter). On the simulated imager, the coincidence detection efficiency at the center of FOV was 3.85 × 10-6, the spatial resolution was 7.0 mm. On the prototype imager, the corresponding values were 3.20 × 10-6and 6.7 mm, respectively. Simulated hot-rod and experimental cardiac phantom studies demonstrate the first three-dimensional cascade gamma coincidence imager is fully functional.

Permutation entropy (PE) and weighted permutation entropy (WPE) are indexes of the complex system. In this paper, the nonlinear sequence of two chaotic states is simulated by Logistic mapping, and the effectiveness of the PE and WPE algorithms in chaotic state recognition is compared and analyzed with different sliding step sizes. The results show that the value of WPE changes more obviously than PE in different chaotic states, and the recognition effect of WPE is better than PE in dynamic states, which can provide theoretical support for further analyzing the complexity characteristics of actual data.

In the traditional power system, the voltage regulation and frequency modulation control method used for boiler induced draft fan is limited in control accuracy. With the improvement of furnace pressure change accuracy, higher requirements are put forward for motor control algorithm. This paper studies permanent magnet synchronous motor (PMSM) as the executive part of induced draft fan servo control system, and adopts FOC control method based on space vector pulse width modulation (SVPWM). Firstly, the simulation model of SVPWM pulse width modulation algorithm is established by MATLAB to provide theoretical support for the subsequent debugging algorithm; When using FPGA to realize SVPWM modulation algorithm, FPGA has the advantages of high reliability and high real-time processing, which provides theoretical support and application guidance for the realization of high-precision motor control of boiler induced draft fan in power system.

Aiming at the problem of false detection and missed detection of small targets and occluded targets in the process of pedestrian detection, a pedestrian detection algorithm based on improved multi-scale feature fusion is proposed. First, for the YOLOv4 multi-scale feature fusion module PANet, which does not consider the interaction relationship between scales, PANet is improved to reduce the semantic gap between scales, and the attention mechanism is introduced to learn the importance of different layers to strengthen feature fusion; then, dilated convolution is introduced. Dilated convolution reduces the problem of information loss during the downsampling process; finally, the K-means clustering algorithm is used to redesign the anchor box and modify the loss function to detect a single category. The experimental results show that the improved pedestrian detection algorithm in the INRIA and WiderPerson data sets under different congestion conditions, the AP reaches 96.83% and 59.67%, respectively. Compared with the pedestrian detection results of the YOLOv4 model, the algorithm improves by 2.41% and 1.03%, respectively. The problem of false detection and missed detection of small targets and occlusion has been significantly improved.