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In this paper, the effect of D0 temperature, Kappa factor and the final pH value on bleaching sulfate bleached pine wood pulp was studied. The results showed that the bleaching efficiency was better when the pH value was 4, and the amount of absorbable organic halogen (AOX) in the bleaching wastewater was decreased. The Kappa factor is linear with the whiteness in the range of 0–0.15. With the increase of the Kappa factor, the amount of AOX in bleaching wastewater of D0 and Ep gradually increases. High temperature bleaching can reduce AOX production, but some fibers are hydrolyzed, leading to a decrease in pulp viscosity. The effects of chlorine dioxide solution adding sodium dihydrogen phosphate (NaH2PO4) and dimethylsulfoxide (DMSO) on pulp bleaching were investigated. The results showed that both solutions could reduce the amount of AOX in bleaching wastewater. Among them, the addition of NaH2PO4 in chlorine dioxide increased pulp whiteness, while the addition of DMSO was the opposite. Scanning electron microscope showed that a small amount of hollow cracks and more voids appeared on the surface of pulp fibers after the addition of NaH2PO4. Pulp fibers bleached by the chlorine dioxide adding DMSO have more folds and less voids on the surface. The surface wrinkles of pulp fibers increased with the addition of DMSO and the voids were less. FT-IR showed that the number of chromophore groups in the pulp bleached by chlorine dioxide adding NaH2PO4 were decreased. However, the lignin characteristic absorption peak in the pulp bleached by chlorine dioxide adding DMSO increased at the intensity of 1062 and 1160 cm−1, which indicated that there were more residual chromophore groups.

In this paper, we clarify the duplicated electromagnetic characteristics between the proposed two-beam overmoded multi-gap structure published in the paper titled “Tractable resonant structure with two nonuniform beams for a high-power 0.22-THz extended interaction oscillator” [Bi et al., IEEE Electron Device Lett. 42(6), 931–934 (2021)] and conventional multi-gap structures from the physical concept point of view. The replacement of the TE10 mode by the TE30 mode used in the interaction gaps provides the basis for the duplicated electromagnetic field distributions and frequencies between the two structures. The concept of magnetic coupling is proposed to support the resonant condition that supports duplication of the TE30 field and the frequency of the single-gap structure into the periodic standing-wave field of the multi-gap structure. With this concept, the perturbation of different axial phase shifts across one period to the standing-wave field of the TE30-0 mode is analyzed to clarify the profiles of the dispersion curves of the TE30 mode in the overmoded structure and the TE10 mode in the conventional structure. To demonstrate the profiles, a 220-GHz overmoded and conventional structure with nine gaps is designed, and their dispersion curves are obtained by using eigenmode simulations. In addition, the effect of the difference in the boundary conditions of the geometries of these two structures on the magnetic field distribution is analyzed to demonstrate the duplication of the ohmic losses between the two structures. The physical analysis in the duplicated electromagnetic characteristics lays a foundation for the promising design of the overmoded structure with two beams for high frequency extended interaction oscillators.

High-precision wind power prediction could reference the optimal dispatch and stable operation of the power system. This paper proposes an adaptive hybrid optimization algorithm that integrates decomposition and reconstruction to effectively explore the potential characteristics and related factors of wind power output and improve the accuracy of short-term wind power prediction. First, the extreme-point symmetric mode decomposition is used to analyze the periodicity, trend, and abrupt characteristics in the original wind power sequence and form multiple intrinsic mode functions with local time-domain characteristics. Then, considering the similarity of the feature sequence and the efficiency of the prediction algorithm, the permutation entropy is used to reconstruct the components with close time-domain characteristics to form subsequences that could reflect different spectral characteristics. Then, the improved maximum relevance minimum redundancy-the long short-term memory-the adaptive boosting algorithm model is used to determine the prediction model structure, parameters, and optimal feature factors of the subsequences. Finally, the prediction results of each subsequence are integrated to obtain the final wind power. Taking a wind farm in northern Shaanxi as the application object, the prediction accuracy and efficiency of the methods proposed in this paper are compared in terms of the decomposition method, prediction model, and prediction timeliness. The results show that in the 15 min to 3 h forecast periods, compared with other models, the mean absolute error and root mean square error of the proposed model are increased. At the same time, as the forecast period grows, the superiority of the proposed method is more prominent.

This paper takes the annular solar eclipse that occurred in China on June 21, 2020, as the background and conducts tests and analysis of shortwave timing sky wave signals. The test group continuously tested the signal field strength data from June 20, 2020, to June 23, 2020. The results show that the shortwave signal field strength on June 21, the day of the annular eclipse, is significantly weaker than that on two other days—before and during the annular eclipse—and there are three obvious jumps in the field strength value. (1) The first jump occurs more than one hour before the annular eclipse, and then, the field strength has an oscillatory attenuation. Between the first jump and the second jump, the overall change trend of the field strength value is an oscillatory decline one. (2) About 25 min before the beginning of the eclipse, the second jump of the field strength occurs; from the second jump to the third jump, that is, before the occurrence of the beginning of the eclipse and the transition phase from the beginning to the middle of the eclipse, the value of the field strength has an oscillatory increase. (3) During the period of 8:00–8:10, the field strength shows a third jump. Although the field strength oscillates after the third jump, it has no obvious increasing or decreasing trend. Based on the results of previous studies on the annular eclipse on that day and the analysis of the theoretical model of radio wave propagation, this paper preliminarily considers that the change in signal field strength is supposed to be caused by the impact of the outbreak of the annular eclipse on the ionosphere. When the annular eclipse occurred, the sunlight reaching the ground is blocked by the Moon, and the ionization degree of electrons in the ionosphere is reduced, resulting in an increase in the penetration factor, and the overall performance of the shortwave signal reaching the ground is weakened.

The aircraft skin is an important component of the aircraft, and its integrity affects the flight performance and safety performance of the aircraft. Damage detection technology with ultrasonic nondestructive testing as the core has played an important role in aircraft skin damage detection. Due to the difficulty in aircraft skin detection, relying solely on the ultrasonic A-scan equipment has very low detection efficiency. The introduction of artificial intelligence can effectively improve the detection efficiency. This paper establishes the one-dimensional convolutional neural network and single shot multibox detector network, which is based on the SSD network and uses dilated convolution to improve the real-time tracking of the ultrasonic probe. At the same time, 1DCNN is introduced to classify the ultrasonic A-scan signal. Finally, the detection results of the two are combined to achieve the reflection of the internal conditions of the aircraft skin. After testing, the algorithm can identify skin simulation specimens, and its recognition accuracy is 96.5%, AP is 90.9%, and kappa is 0.996. Comparing the improved SSD network with networks such as SSD, YOLOv3, and Faster R-CNN, the results show that the improved network used in this paper is more excellent and effective. At the same time, the detection effects of four types of optimization algorithms and five learning rates are studied, and finally, the corresponding signal classification model adopts Adam and the learning rate of 0.0001 has the best effect.

This paper proposes a complementary frequency electromagnetic gyroscope. In this gyroscope, a voltage-controlled oscillator (VCO) is applied to generate complementary frequency signals and the angular rate detection is realized based on a phase-locked loop. The complementary frequency electromagnetic gyroscope can be fully realized by micro-electronic technology, which is beneficial to the miniaturization of the angular rate measurement system and has a wide application prospect. The complementary frequency electromagnetic gyroscope extends the application of the Sagnac effect and replaces the optical signal with the electromagnetic pulse signal. It can make full use of the advantages of microelectronic technology and microwave technology to realize the miniaturization of measuring components and even realize the system on a chip. In this paper, the mathematical model of the complementary frequency electromagnetic gyroscope is established and verified by simulation analysis. Theoretical analysis shows that the measured angular rate is proportional to the relative frequency difference of complementary VCO output. The simulation results indicate that the sensitivity of the complementary frequency gyroscope is 1 × 10−5 rad/s and is insensitive to noise. When the signal-to-noise ratio is lower than 0 dB, the gyroscope still has good angular rate measurement accuracy.

It was of great significance to study the damage evolution mechanism of geomaterial/soil interfaces in landfill seepage control systems to evaluate the slope instability of landfill sites with high dam and large storage capacity. In this paper, the interfacial shear behaviors of geomaterial/soil were studied by drawing test. At the same time, the interface meso-test was used to analyze the change characteristics of geomaterial/soil interfaces during the drawing process. The results showed that under the synergistic action of the interface friction of geotextile/geomembrane and the reinforced shear band at the interface of geotextile/soil, the shear strength and interface stability of the composite geomaterial/soil interface not only increased but also improved. In order to describe the shear deformation and softening characteristics of the geomaterial/soil interfaces, a constitutive model of the interface was established based on the statistical damage theory to study the damage evolution mechanism of the interface under the action of drawing. The fitting results showed that the fitting correlation between the interface constitutive model established in this paper and the shear strength–drawing displacement curves obtained from the tests was greater than 0.97, which indicated that the constitutive model could better describe the shear deformation characteristics of the interface.

The use of low-emissivity coatings as an infrared (IR) stealth method for weaponry is an important guarantee for the survival of weaponry in the battlefield. The damage on low-emissivity coatings leads to a significant drop in the IR stealth performance of weaponry. Therefore, this paper carries out a research on the intelligent damage identification of low-emissivity coatings based on convolutional neural networks (CNNs). A low-emissivity coating damage dataset with the characteristics of large changes in brightness, distortion of images, and large changes in the target scale is constructed. A composite network (CompoNet) based on feature fusion is designed to extract the detailed features of damage and identify damage types. Compared with VGG16, the damage identification accuracy of CompoNet is improved by 5.49% points. The idea of specific feature extraction layers (SFELs) is proposed. Three SFELs are designed to extract the color, texture, and contour features, which are important basis for judging damage types. The SFEL accelerates the convergence of the model and increases the identification accuracy of the model by 2.02% points. The generative adversarial network is used to generate low-emissivity coating damage images, which solves the problem that the number of damage images collected is small due to practical difficulties. The final damage identification accuracy of the CompoNet fused with SFELs (CompoNet with SFELs) constructed in this paper reaches 99.17%, which is much higher than other generic CNNs.

The gas spark switch is the most used key device in pulsed power systems. As a difficult problem affecting the performance of the gas spark switch, electrode erosion has always been of wide concern and has been studied by scholars. In order to reduce electrode erosion, the erosion resistance of the electrode materials is particularly critical. At present, researchers at home and abroad mainly perform a large number of experiments to compare the erosion resistance of different electrode materials, which require a lot of time and are expensive. Based on the theoretical derivation of the erosion heat conduction process and the analysis of the molten pool movement process, a theoretical prediction model of erosion resistance of electrode materials is established in this paper. The prediction results of this model are consistent with the experimental results of most researchers in the past. In order to further verify the accuracy of this model, this paper selected six electrode materials [stainless steel, brass, RHEAs (Refractory High Entropy Alloys), 90WCu alloy, 70WCu alloy, and 50WCu alloy] tested for 10 000 times under the experimental conditions of a peak current of 30 kA, a single discharge charge transfer of 78 mC, and 2 bars dry air. The final experimental results show that the six electrode materials ranked from weak to strong in erosion resistance: brass, stainless steel, 50WCu, 70WCu, RHEAs, and 90WCu, which is consistent with the prediction results of the model.

The temperature of the high-power inductively coupled plasma jet is very high, and its temperature is difficult to measure directly. The heat flux becomes a thermodynamic characteristic to measure the plasma jet. The existing heat flux calculation method is based on the temperature change rate after the response time. The slug is required to stay in the high enthalpy jet area for a longer time. With the slug temperature reaching the melting point as the upper limit, the shorter the residence time, the greater the upper limit of the measured heat flux. In this paper, the first-order transient solution is added to the steady-state solution of temperature (the calculation equation of the existing method), which can shorten the response time. The shortening of the response time can reduce the residence time of the slug in the jet region, and the reduction in the residence time can increase the upper limit of the calorimeter heat flux measurement. This paper uses numerical simulation and experimental methods to verify that the steady-state solution method and the first-order transient solution method can obtain consistent heat flux results. Using the first-order transient solution method can reduce the residence time of the slug calorimeter in the jet region. According to the shortening of the residence time, the method of using the first-order transient solution can increase the upper limit of the heat flux measurement by more than 25%.

This paper presents a methodology to simulate the nonlinear free surface flow around an advancing ship. This methodology is based on the Moving Particle Semi-implicit (MPS) method, which is widely used to simulate the incompressible fluid flow. In this paper, the original MPS method is modified in order to analyze effectively the nonlinear free surface flow around an advancing ship. Several treatment techniques are newly proposed, and the original MPS method is modified by combining these techniques with other previous research studies. The proposed techniques include the Laplacian compensation model in the region near the body boundary, the collision model between fluid particles and wall particles, and some treatments for the opened boundary. The accuracy of the modified MPS method is verified through the numerical simulations on two benchmark problems for the performance evaluation of the particle methods and on the flows around both the wedged body and model ship. The numerical results demonstrate that the modified MPS method can be effectively applied to the simulation of nonlinear free surface flow around an advancing ship in marine engineering.

Generation of spontaneous magnetic fields (SMFs) is one of the most interesting phenomena accompanying an intense laser–matter interaction. One method of credible SMFs measurements is based on the magneto-optical Faraday effect, which requires simultaneous measurements of an angle of polarization plane rotation of a probe wave and plasma electron density. In classical polaro-interferometry, these values are provided independently by polarimetric and interferometric images. Complex interferometry is an innovative approach in SMF measurement, obtaining information on SMF directly from a phase–amplitude analysis of an image called a complex interferogram. Although the theoretical basis of complex interferometry has been well known for many years, this approach has not been effectively employed in laser plasma research until recently; this approach has been successfully implemented in SMF measurement at the Prague Asterix Laser System (PALS). In this paper, proprietary construction solutions of polaro-interferometers are presented; they allow us to register high-quality complex interferograms in practical experiments, which undergo quantitative analysis (with an original software) to obtain information on the electron density and SMFs distributions in an examined plasma. The theoretical foundations of polaro-interferometric measurement, in particular, complex-interferometry, are presented. The main part of the paper details the methodology of the amplitude–phase analysis of complex interferograms. This includes software testing and examples of the electron density and SMF distribution of a laser ablative plasma generated by irradiating Cu thick planar targets with an iodine PALS laser at an intensity above about 1016 W/cm2.

The self-excitation of asymmetric modes is one of the main factors limiting the long-pulse operation of the relativistic triaxial klystron amplifier (TKA). Research studies have revealed that the asymmetric TM modes with negative beam loading conductance (Ge/G0) in the bunching cavities are the main culprits of self-excitation. The existing studies focus on passively destroying the growth of asymmetric TM modes, but we attempt to actively suppress their self-excitation in this paper. Investigation results demonstrate that the employment of single-gap bunching cavities can significantly reduce the risk of self-excitation of asymmetric TM modes, as the Ge/G0 of asymmetric TMn11 modes in single period structures are positive. The current modulation capacity of a single-gap bunching cavity, however, is not sufficient, so a cascade structure consisting of two groups of bunching cavities is employed to compensate for this deficiency. Based on the above conclusions, an X-band TKA device with four single-gap beam–wave interaction cavities is proposed and investigated in this paper. The three-dimensional particle-in-cell simulation results demonstrate that there is no self-excitation of asymmetric modes in the proposed X-band TKA device.

A novel design for complete transfer and robust three-waveguide coupler is presented in this paper, which employs shortcut to adiabaticity (STA) based on stimulated Raman adiabatic passage (STIRAP). Most recently, some remarkable papers on STA of STIRAP [Phys. Rev. A 94(6), 063411 (2016) and Nat. Comm. 7, 12479 (2016)] have been proposed in both theoretical and experimental configurations. In this paper, we propose to design a novel three-waveguide coupler by employing STA based on STIRAP, which can achieve much shorter device length and also maintain the robust performance against perturbations on device geometry parameters compared to previous devices. This finding significantly improves the performance and fabrication of integrated optical devices to build up more compactable devices.

Coaxial slow wave structures have always been used to enhance the power handling capacity in the relativistic O-type Cherenkov oscillators generally. However, little attention has been paid to the regularity and the problem it may bring by using large average radius. The aim of this study was to investigate the high-frequency characteristics of coaxial slow wave structures in order to evaluate the influence of the radial dimension comprehensively. The results indicate that a large overmoded ratio can make the power handling capacity increase significantly, but as a result, it will bring some problems such as low efficiency, long starting time, and the difficulty in mode control. In addition, this paper also gives some suggestions and precautions for using large radial dimensions. The conclusion of this paper has strong applicability for the design of coaxial slow wave structures.

C6F12O can be used in gas-insulated equipment due to its excellent insulation properties. The purpose of this paper is to calculate the total electron-impact ionization cross section to evaluate the dielectric strength of the molecule using the Deutsch–Märk formula. First, according to the calculation method of quantum chemistry, the structure of the molecule is optimized. Three different methods, such as Mulliken population analysis, C-squared population analysis, and natural atomic orbital (NAO), are used to calculate the molecular orbital components, and then the molecular collision cross section is obtained. The influence of different weighting factors on the calculation results is analyzed. The validity of the proposed method is verified by the calculation results of H2O, C3H6O, and C5F10O. The results show that the calculation value with the NAO method is closer to the experimental results, which provides a reference for the calculation and analysis of the collision cross section of C6F12O. The calculation results in this paper can provide basic data for further calculation of the dielectric strength of C6F12O.

In this paper, a coaxial electrostatic wiggler with corrugated inner and outer walls is investigated theoretically. The field distributions in this wiggler correspond to the special solution of a Laplace equation in a cylindrical coordinate system with two sinusoidal ripple boundaries. Through numerical analysis and comparison to the coaxial electrostatic wiggler with a corrugated outer wall, the results indicate that in a coaxial electrostatic wiggler with corrugated inner and outer walls, electric field undulation can be enhanced. The particle-in-cell simulation further demonstrates that the electrons can be modulated deeply.In this paper, a coaxial electrostatic wiggler with corrugated inner and outer walls is investigated theoretically. The field distributions in this wiggler correspond to the special solution of a Laplace equation in a cylindrical coordinate system with two sinusoidal ripple boundaries. Through numerical analysis and comparison to the coaxial electrostatic wiggler with a corrugated outer wall, the results indicate that in a coaxial electrostatic wiggler with corrugated inner and outer walls, electric field undulation can be enhanced. The particle-in-cell simulation further demonstrates that the electrons can be modulated deeply.

This paper aims to propose a tangential contact model of a lap joint interface with non-Gaussian surfaces. Relying on the full-stick contact condition, the elastic–plastic deformation of a single asperity and the penetration-dependent friction coefficient are considered in this model. The Johnson system is utilized to generate non-Gaussian asperity height distributions. Furthermore, the physical asperity model and the phenomenological Iwan model are combined to obtain a continuous and convergent Iwan solution by the dimensional analysis method. The initial tangential stiffness, the tangential force required for gross slip, and the slip index of lap joints reveal the hysteresis loop shape, describing the tangential response completely and uniquely, and the first two parameters are proved to own statistical characteristics. Next, the effects of topography parameters on the initial tangential stiffness, the tangential force/displacement required for gross slip, and the slip index are analyzed. Comparisons among the proposed model, the published models, and the published experimental results have also been made. The proposed model is shown to be consistent with the experimental results when the tangential load is insufficient to cause gross slip, while an error is produced when gross slip happens. Additionally, the error could be reduced in the calibrated model.This paper aims to propose a tangential contact model of a lap joint interface with non-Gaussian surfaces. Relying on the full-stick contact condition, the elastic–plastic deformation of a single asperity and the penetration-dependent friction coefficient are considered in this model. The Johnson system is utilized to generate non-Gaussian asperity height distributions. Furthermore, the physical asperity model and the phenomenological Iwan model are combined to obtain a continuous and convergent Iwan solution by the dimensional analysis method. The initial tangential stiffness, the tangential force required for gross slip, and the slip index of lap joints reveal the hysteresis loop shape, describing the tangential response completely and uniquely, and the first two parameters are proved to own statistical characteristics. Next, the effects of topography parameters on the initial tangential stiffness, the tangential force/displacement required for gross slip, and the slip index are analyzed. Comparisons am...

This paper proposes a novel S-parameter retrieval method to extract the arbitrary permittivity and permeability tensors of general biaxial anisotropic materials. The proposed method uses three measurements of the reflection and transmission coefficients of a simple normal-incident circularly polarized plane wave. The circular polarization is employed to overcome the ambiguity attributed to the discontinuities in the extracted possible positive and negative values of the permittivity and permeability tensors for natural or synthesized anisotropic materials. The mathematical procedure of the proposed method directly relates the combined parameters deduced from the circularly polarized wave components to the tensor permittivity and permeability linear components while avoiding the need for heavy computations or optimization schemes. This simple procedure successfully overcomes the limitations to the usable frequency band and the material losses observed in previously published retrieval techniques for lossless and lossy anisotropic materials at low- and high-frequency regions. The retrieved tensor elements are validated by comparison to analytical data obtained from solving the original electromagnetic problem using the Berreman 4 × 4 matrix method after extending it to the case of circularly polarized fields.This paper proposes a novel S-parameter retrieval method to extract the arbitrary permittivity and permeability tensors of general biaxial anisotropic materials. The proposed method uses three measurements of the reflection and transmission coefficients of a simple normal-incident circularly polarized plane wave. The circular polarization is employed to overcome the ambiguity attributed to the discontinuities in the extracted possible positive and negative values of the permittivity and permeability tensors for natural or synthesized anisotropic materials. The mathematical procedure of the proposed method directly relates the combined parameters deduced from the circularly polarized wave components to the tensor permittivity and permeability linear components while avoiding the need for heavy computations or optimization schemes. This simple procedure successfully overcomes the limitations to the usable frequency band and the material losses observed in previously published retrieval techniques for lossle...

Cell photoacoustic detection of acoustic signals has serious problems of transmission loss and difficulty in acquisition. Based on the acoustic transmission characteristics of acoustic supermaterials, the acoustic wave directional transmission model is designed using COMSOL software, and a finite element simulation experiment was carried out. Experiments show that the model designed in this paper has good sound wave focusing and acoustic wave directional transmission effects. According to the specific application in different environments, this paper designs a variety of transmission models with different structures and carries out comparative experiments to verify the influence of complex model structures on the directional transmission of sound waves. At the same time, the experimental analysis of the acoustic wave directional transmission effect of the model under different frequency segments is carried out, and the possibility of acoustic wave logic operation is verified. Models can be applied to high frequency acoustic signal acquisition and sound wave transmission in complex environments. These studies have important significance for the development of cell photoacoustic detection technology and the application of metamaterial structures and have good practical merit.

In this paper, we propose a reflectarray metasurface to generate two modes of orbital angular momentum (OAM) in two orthogonal directions of polarization. The metasurface comprises dual-bowtie elements of various sizes. By varying the size of the geometry, the element can simultaneously alter the phases of reflection of both polarizations. In the design, equivalent circuit models of the unit cell in both the orthogonal direction and the direction of excitation are built and discussed. These models are used to explain the results of the simulation and can help accelerate the optimization process when designing other reflective metasurfaces. Both the first- and second-order metasurface reflectarrays were simulated and measured at 10 GHz, and the results confirmed that different OAM modes can be generated in two orthogonal directions of polarization. Compared with the prevalent design, the proposed one is more compact as it has only one layer and does not require active components. We also simulated and measured the first-order metasurface reflectarray at multiple frequencies, and the results from 9.2 to 10.5 GHz show that it can generate the two polarized OAMs independently in broadband.In this paper, we propose a reflectarray metasurface to generate two modes of orbital angular momentum (OAM) in two orthogonal directions of polarization. The metasurface comprises dual-bowtie elements of various sizes. By varying the size of the geometry, the element can simultaneously alter the phases of reflection of both polarizations. In the design, equivalent circuit models of the unit cell in both the orthogonal direction and the direction of excitation are built and discussed. These models are used to explain the results of the simulation and can help accelerate the optimization process when designing other reflective metasurfaces. Both the first- and second-order metasurface reflectarrays were simulated and measured at 10 GHz, and the results confirmed that different OAM modes can be generated in two orthogonal directions of polarization. Compared with the prevalent design, the proposed one is more compact as it has only one layer and does not require active components. We also simulated and meas...

The simulation of the electromagnetic wave propagation plays an important role in solving the communication blackout issue. Finite element analysis software package COMSOL is employed by us to model the electromagnetic wave propagation in the presence of the non-uniform reentry plasma sheath in this paper. The propagation characteristics of the electromagnetic wave are analyzed by the observation of the field distributions. The electromagnetic wave with s polarization begins to attenuate as an exponential function at the cut-off position. The mode conversion takes place for the p polarization wave when the real part of the plasma permittivity is close to 0. The wave reflection, transmission, and absorption coefficients as a function of the frequency are calculated and analyzed. The absolute agreements between the results calculated by COMSOL model and by the layered model are achieved. The difference of the coefficients between s and p polarization waves can be explained by the presence or absence of the mode conversion. Conclusions in this paper can be the foundation to employ the COMSOL to study the interactions between the electromagnetic wave and the plasma.

This paper presents the general solution to the accuracy problems in magnetic field based positioning systems needed for inductive charging of electric vehicles. These systems process a periodic magnetic signal emitted by the charging coil for its localization. The amplitude is highly distorted by the ferromagnetic vehicle according to an unknown transformation f. Thus, this paper discusses how f is affected by the magnetization process in the material. It is shown that f is proportional to the incremental permeability μΔ which depends on the non-deterministic operating point on the material’s hysteresis curve. However, in this research the same problem is described for the first time from the perspective of Hopkinson’s law, showing that the hysteresis curve is extremely flattened. As a consequence μ△ has in all possible operating points the same value, meaning that f is reproducible, measurable and depends only on the distance d to the coil. Further, it is deduced that f(d) is a strictly monotonously decreasing function, which enables unambiguous coil detection. Finally, the non-monotonous structure of f close to the coil is discussed, and why it is negligible for positioning.This paper presents the general solution to the accuracy problems in magnetic field based positioning systems needed for inductive charging of electric vehicles. These systems process a periodic magnetic signal emitted by the charging coil for its localization. The amplitude is highly distorted by the ferromagnetic vehicle according to an unknown transformation f. Thus, this paper discusses how f is affected by the magnetization process in the material. It is shown that f is proportional to the incremental permeability μΔ which depends on the non-deterministic operating point on the material’s hysteresis curve. However, in this research the same problem is described for the first time from the perspective of Hopkinson’s law, showing that the hysteresis curve is extremely flattened. As a consequence μ△ has in all possible operating points the same value, meaning that f is reproducible, measurable and depends only on the distance d to the coil. Further, it is deduced that f(d) is a strictly monotonously dec...

In this paper, we report a novel approach based on a lensless Synthetic Optical Holography (SOH) that is aimed to recover the complex scattered field from buried surfaces at different wavelengths with sub-nanometric spectral resolution, without affecting the phase retrieval in depth. The proposed technique is applied to characterize and image the field scattered from a rough embedded surface of a microfluidic channel. The real and imaginary part of the random complex field revealed the presence of 2D optical vortices at each location in which a phase singularity is located. A statistical study of optical vortices is presented and the high spectral resolution is exploited to study the behavior of topological charges with the frequency shift.In this paper, we report a novel approach based on a lensless Synthetic Optical Holography (SOH) that is aimed to recover the complex scattered field from buried surfaces at different wavelengths with sub-nanometric spectral resolution, without affecting the phase retrieval in depth. The proposed technique is applied to characterize and image the field scattered from a rough embedded surface of a microfluidic channel. The real and imaginary part of the random complex field revealed the presence of 2D optical vortices at each location in which a phase singularity is located. A statistical study of optical vortices is presented and the high spectral resolution is exploited to study the behavior of topological charges with the frequency shift.

The sheath electric field is localized with a thickness of only several Debye lengths. It widely exists at plasma boundaries and in some cases can be very intense. Previous diagnoses of an intense, localized sheath electric field could only deliver the spatially averaged amplitude of the field. The sheath’s spatial structures remain unresolved. In this paper, we numerically demonstrate the three-dimensional reconstruction of a cylindrically symmetric sheath electric field by means of the Abel inversion in combination with a correction of the spatial dislocation in the inversion process. By employing a divergent or/and relativistic proton beam for radiography of the sheath region, it is found that the crossings of the proton trajectories can be prevented and the linearity requirement for the Abel inversion can be satisfied. A sheath electric field with an amplitude of about 1×1011 V/m and a thickness of sub-μm level is well reconstructed with a 120 MeV proton beam. The inter dependences of the reconstruction on the proton beam energy, energy spread, beam divergence, and the amplitude of the sheath are discussed.The sheath electric field is localized with a thickness of only several Debye lengths. It widely exists at plasma boundaries and in some cases can be very intense. Previous diagnoses of an intense, localized sheath electric field could only deliver the spatially averaged amplitude of the field. The sheath’s spatial structures remain unresolved. In this paper, we numerically demonstrate the three-dimensional reconstruction of a cylindrically symmetric sheath electric field by means of the Abel inversion in combination with a correction of the spatial dislocation in the inversion process. By employing a divergent or/and relativistic proton beam for radiography of the sheath region, it is found that the crossings of the proton trajectories can be prevented and the linearity requirement for the Abel inversion can be satisfied. A sheath electric field with an amplitude of about 1×1011 V/m and a thickness of sub-μm level is well reconstructed with a 120 MeV proton beam. The inter dependences of the reconstructi...

The butterfly gyroscope is simple to manufacture and it is considered as one kind of MEMS gyroscope with high sensitivity due to its unique structure. In reality, fabrication imperfections result in non-ideal geometries in the resonator, which in turn causes the quadrature error. The quadrature error has a great influence on the performance of the sensors in Micro and Nano scale, such as the zero-rate output (ZRO), the detection resolution and the dynamic range. However, the fact that the mechanical parameters of resonators are unknown (due to fabrication variation, fluctuations with temperature and aging) poses serious challenges. This paper presents a simple, yet effective method of quadrature compensation in butterfly resonator by electrostatic tuning. Theoretical calculation of quadrature error in butterfly gyroscope is carried out, establishing the mathematical model of quadrature compensation. Then, the simulation analysis is conducted to further analyze the mechanism of quadrature error and the method of quadrature compensation. Also, 5 butterfly gyroscopes fabricated on the same silicon wafer are selected for the experiment of quadrature compensation and the ZRO of the butterfly gyroscopes improves up to two orders of magnitude with quadrature cancellation, showing the feasibility of the proposed approach to quadrature compensation in the butterfly gyroscope. Finally, the way to decrease the direct current voltage VT required for suppressing the quadrature error is discussed. What is more, the method is not only suitable for the butterfly gyroscope, but also can be applied to other sensors in the Micro and Nanoscale.The butterfly gyroscope is simple to manufacture and it is considered as one kind of MEMS gyroscope with high sensitivity due to its unique structure. In reality, fabrication imperfections result in non-ideal geometries in the resonator, which in turn causes the quadrature error. The quadrature error has a great influence on the performance of the sensors in Micro and Nano scale, such as the zero-rate output (ZRO), the detection resolution and the dynamic range. However, the fact that the mechanical parameters of resonators are unknown (due to fabrication variation, fluctuations with temperature and aging) poses serious challenges. This paper presents a simple, yet effective method of quadrature compensation in butterfly resonator by electrostatic tuning. Theoretical calculation of quadrature error in butterfly gyroscope is carried out, establishing the mathematical model of quadrature compensation. Then, the simulation analysis is conducted to further analyze the mechanism of quadrature error and the met...

A novel jet-edge structure for flexible piezoelectric harvester is proposed in this paper which converts wind energy into electrical energy by fluid-induced vibrations. This type of the piezoelectric harvester can be applied to self-powered and auxiliary power supplies for aircraft electronic systems. Here, the operational principle for jet-edge flow oscillations is introduced and a specific example of its application is given in this paper. To study the influence of jet, jet outlet with different sizes and the distance between the cantilever beam and the jet outlet were designed and the operating characteristics were investigated by experiments. Results show that, (1) when the aspect ratio of the jet outlet is less than 8.3, the peak voltage increases with the aspect ratio. (2) With the aspect ratio of 8.3, and the distance between the cantilever beam and jet outlet of 80 mm, the piezoelectric device beam vibrates periodically over the wind speed range of 6 to 14 m/s. (3) The piezoelectric energy harvester (with an optimal load of 2.55 MΩ) could generate a maximum power output of ∼83 μW with a resonant frequency of ∼48 Hz at the wind speed of 14 m/s. These results will be helpful to engineering design for energy harvesting devices.

In our previous work, a system of two-dimensional equations for piezoelectric thin-film acoustic wave resonators (FBAR) has been derived and then successfully applied on the free vibration analysis of a finite FBAR plate. In this paper, we analyzed the forced vibrations of FBAR with alternating voltage applied on its electrodes. The derived two dimensional equations were simplified based on straight-crested wave approximations and were rewritten into matrix formalism by state-vector approach. With the knowledge of matrix function, the state-vector equation was successfully solved. Results of admittance were obtained with the dependence on the driving frequency and the aspect ratio. The obtained figure was compared with the frequency spectra obtained in free vibration analysis. Different aspect ratios and quality factors were taken to study the effects of them on the admittance. It is shown that admittance is highly influenced by mode couplings. Thus the work in this paper will be important for the thorough understanding of the coupling vibration of FBAR and its optimization design.In our previous work, a system of two-dimensional equations for piezoelectric thin-film acoustic wave resonators (FBAR) has been derived and then successfully applied on the free vibration analysis of a finite FBAR plate. In this paper, we analyzed the forced vibrations of FBAR with alternating voltage applied on its electrodes. The derived two dimensional equations were simplified based on straight-crested wave approximations and were rewritten into matrix formalism by state-vector approach. With the knowledge of matrix function, the state-vector equation was successfully solved. Results of admittance were obtained with the dependence on the driving frequency and the aspect ratio. The obtained figure was compared with the frequency spectra obtained in free vibration analysis. Different aspect ratios and quality factors were taken to study the effects of them on the admittance. It is shown that admittance is highly influenced by mode couplings. Thus the work in this paper will be important for the thoroug...

In this paper, we have studied the linear and nonlinear propagation of ion acoustic waves in the presence of electrons that follow the generalized (r,q) distribution. It has been shown that for positive values of r, which correspond to a flat-topped electron velocity distribution, the nonlinear ion acoustic waves admit rarefactive solitary structures or density depletions. It has been shown that the generalized (r,q) distribution function provides another way to explicate the density depletions observed by Freja and Viking satellites previously explained by proposing Cairns distribution function.In this paper, we have studied the linear and nonlinear propagation of ion acoustic waves in the presence of electrons that follow the generalized (r,q) distribution. It has been shown that for positive values of r, which correspond to a flat-topped electron velocity distribution, the nonlinear ion acoustic waves admit rarefactive solitary structures or density depletions. It has been shown that the generalized (r,q) distribution function provides another way to explicate the density depletions observed by Freja and Viking satellites previously explained by proposing Cairns distribution function.

Here we present a detailed study on eigenvalues for TM modes. In order to achieve enough accuracy, the spatial harmonics method (SHM) is used to derive the eigenfunction of TM modes in the coaxial cavity with both inner and outer corrugations. After that, the equations can be numerically solved with some constraints. Meanwhile, the influences of the variations of the corrugation parameters on the eigenvalues of TM modes are analyzed carefully, which is helpful for us to learn the distribution rule of the TM modes. In addition, the differences and similarities between TM and TE modes are studied comprehensively to select the suitable mode in the coaxial cavity. The numerical results are presented in this paper, the comparisons are also made with the published results.Here we present a detailed study on eigenvalues for TM modes. In order to achieve enough accuracy, the spatial harmonics method (SHM) is used to derive the eigenfunction of TM modes in the coaxial cavity with both inner and outer corrugations. After that, the equations can be numerically solved with some constraints. Meanwhile, the influences of the variations of the corrugation parameters on the eigenvalues of TM modes are analyzed carefully, which is helpful for us to learn the distribution rule of the TM modes. In addition, the differences and similarities between TM and TE modes are studied comprehensively to select the suitable mode in the coaxial cavity. The numerical results are presented in this paper, the comparisons are also made with the published results.

Recent calculations on the change in radial dimensions of reacting (growing) polyethylene in the gas phase experiencing Lennard Jones and Kihara type potentials revealed that a single reacting polyethylene molecule does not experience polymer collapse. This implies that a transition that is the converse of what happens when molten polyethylene crystallizes, i.e. it transforms from random coil like structure to folded rigid rod type structure, occurs. The predicted behaviour of growing polyethylene was explained by treating the head of the growing polymer chain as myopic whereas as the whole chain (i.e. when under equilibrium conditions) being treated as having normal vision, i.e. the growing chain does not see the attractive part of the LJ or Kihara Potentials. In this paper we provide further proof for this argument in two ways. Firstly we carry forward the exact enumeration calculations on growing self avoiding walks reported in that paper to larger values of number of steps by using Monte Carlo type calculations. We thereby assign physical significance to the connective constant of self avoiding walks, which until now was treated as a purely abstract mathematical entity. Secondly since a reacting polymer molecule that grows by addition polymerisation sees only one step ahead at a time, we extend this calculation by estimating the average atmosphere for molecules, with repulsive potential only (growing self avoiding walks in two dimensions), that look at two, three, four, five ...steps ahead. Our calculation shows that the arguments used in the previous work are correct.

In this paper, a new kind of terahertz oscillator is presented using plasma wave excitation in a resonant tunnel diode (RTD) gated high electron mobility transistor (HEMT). The plasma wave arising from the RTD-gated HEMT is equivalent to active transmission lines and induces negative differential conductance (NDC) of the oscillator. The proposed RTD-gated HEMT oscillator is more compact and has higher oscillation frequency than the transmission line loaded traditional RTD oscillator duo to plasma wave effect. This paper analyses and calculates the oscillation conditions, the relationships between device structures, oscillation frequency and the output power of the oscillator. The presented work may provide a new concept for fabricating terahertz oscillator.

The previous works on whistler waves with electron temperature anisotropy narrated the dependence on plasma parameters, however, they did not explore the reasons behind the observed differences. A comparative analysis of the whistler waves with different electron distributions has not been made to date. This paper attempts to address both these issues in detail by making a detailed comparison of the dispersion relations and growth rates of whistler waves with electron temperature anisotropy for Maxwellian, Cairns, kappa and generalized (r, q) distributions by varying the key plasma parameters for the problem under consideration. It has been found that the growth rate of whistler instability is maximum for flat-topped distribution whereas it is minimum for the Maxwellian distribution. This work not only summarizes and complements the previous work done on the whistler waves with electron temperature anisotropy but also provides a general framework to understand the linear propagation of whistler waves with electron temperature anisotropy that is applicable in all regions of space plasmas where the satellite missions have indicated their presence.The previous works on whistler waves with electron temperature anisotropy narrated the dependence on plasma parameters, however, they did not explore the reasons behind the observed differences. A comparative analysis of the whistler waves with different electron distributions has not been made to date. This paper attempts to address both these issues in detail by making a detailed comparison of the dispersion relations and growth rates of whistler waves with electron temperature anisotropy for Maxwellian, Cairns, kappa and generalized (r, q) distributions by varying the key plasma parameters for the problem under consideration. It has been found that the growth rate of whistler instability is maximum for flat-topped distribution whereas it is minimum for the Maxwellian distribution. This work not only summarizes and complements the previous work done on the whistler waves with electron temperature anisotropy but also provides a general framework to understand the linear propagation of whistler waves with...

This paper introduces the novel self-positioning ability of a sphericon-shaped magnetic millirobot (SSMM) on an inclined surface. The SSMM is comprised of four identical half cones with a cylindrical magnet inserted into the geometric center, and it can roll along a straight line on a surface with repeated rolling cone motions actuated by an external wobbling magnetic field (EWMF). Due to the restoring moment induced by a conservative gravitational force, the SSMM can maintain (self-position) its equilibrium position on the surface, even when the EWMF is removed. This paper derived several equations to quantify the condition in which the SSMM can steadily generate self-positioning motions. It also examined the self-positioning ability of the SSMM by constructing a prototype SSMM and demonstrating its rolling and self-positioning motions by using a magnetic navigation system.

This paper presents an improved flux intensifying permanent magnet embedded salient pole wind generator (FI-PMESPWG) with mirror symmetrical magnetizing directions permanent magnet (PM) for improving generator’s performances. The air-gap flux densities, the output voltage, the cogging torque and the d- and q-axis inductances of FI-PMESPWG are all calculated and analyzed by using the finite element method (FEM). To highlight the advantages of the proposed FI-PMESPWG, an original permanent magnet embedded salient pole wind generator (PMESPWG) model is adopted for comparison under the same operating conditions. The calculating results show that the air-gap flux densities of FI-PMESPWG are intensified with the same magnet amounts because the PMs are set in a form of V shape in each pole. The difference between d-axis inductance and q-axis inductance of the proposed FI-PMESPWG is reduced. Thus, the output power of the proposed FI-PMESPWG reaches a higher value than that of the original PMESPWG at the same current phase angle. The cogging torque is diminished because the flux path is changed. All the analysis results indicate that the electromagnetic characteristics of the proposed FI-PMESPWG are significantly better than that of the original PMESPWG.This paper presents an improved flux intensifying permanent magnet embedded salient pole wind generator (FI-PMESPWG) with mirror symmetrical magnetizing directions permanent magnet (PM) for improving generator’s performances. The air-gap flux densities, the output voltage, the cogging torque and the d- and q-axis inductances of FI-PMESPWG are all calculated and analyzed by using the finite element method (FEM). To highlight the advantages of the proposed FI-PMESPWG, an original permanent magnet embedded salient pole wind generator (PMESPWG) model is adopted for comparison under the same operating conditions. The calculating results show that the air-gap flux densities of FI-PMESPWG are intensified with the same magnet amounts because the PMs are set in a form of V shape in each pole. The difference between d-axis inductance and q-axis inductance of the proposed FI-PMESPWG is reduced. Thus, the output power of the proposed FI-PMESPWG reaches a higher value than that of the original PMESPWG at the same curr...

This paper is aimed to investigate the array plasma antenna parameters to help the optimization of an array plasma antenna. Single plasma antenna is transformed into array plasma antenna by changing the operating parameters. The re-configurability arises in the form of striations, due to transverse bifurcation of plasma column by changing the operating parameters. Each striation can be treated as an antenna element and system performs like an array plasma antenna. In order to achieve the goal of this paper, three different configurations of array plasma antenna (namely Array 1, Array 2 and Array 3) are simulated. The observations are made on variation in antenna parameters like resonance frequency, radiation pattern, directivity and gain with variation in length and number of antenna elements for each array plasma antenna. Moreover experiments are also performed and results are compared with simulation. Further array plasma antenna parameters are also compared with monopole plasma antenna parameters. The study of present paper invoke the array plasma antenna can be applied for steering and controlling the strength of Wi-Fi signals as per requirement.

This paper analyzes the MHD flow of micropolar fluid induced by peristaltic waves passing through the porous saturated channel at large Reynolds number. The flow model is formulated in the absence of assumptions of lubrication theory which yields the governing equations into a non-linear set of coupled partial differential equations which allows studying the peristaltic mechanism at non-zero Reynolds and wave numbers. The influence of other involved parameters on velocity, stream function and microrotation are discussed through graphs plotted by using Galerkin’s finite element method. Besides that, the phenomena of pumping and trapping are also analyzed in the later part of the paper. To ensure the accuracy of the developed code, obtained results are compared with the results available in the literature and found in excellent agreement. It is found that the peristalsis mixing can be enhanced by increasing Hartmann number while it reduces by increasing permeability of the porous medium.

Most of the published papers regarding the design of flux-switching permanent magnet machines are focused on the analysis and optimization of electromagnetic or mechanical behaviors, however, the evaluate of the parameter sensitivities have not been covered, which contrarily, is the main contribution of this paper. Based on the finite element analysis (FEA) and simplified equivalent magnetic circuit, the method proposed in this paper enables the influences of parameters on the electromagnetic performances, i.e. the parameter sensitivities, to be given by equations. The FEA results are also validated by experimental measurements.

Propagation characteristics of electromagnetic (EM) waves in partially ionized plasma slabs are studied in this paper. Such features are significant to applications in plasma antennas, blackout of re-entry flying vehicles, wave energy injection to plasmas, and etc. We in this paper developed a theoretical model of EM wave propagation perpendicular to a plasma slab with a one-dimensional density inhomogeneity along propagation direction to investigate essential characteristics of EM wave propagation in nonuniform plasmas. Particularly, the EM wave propagation in sub-wavelength plasma slabs, where the geometric optics approximation fails, is studied and in comparison with thicker slabs where the geometric optics approximation applies. The influences of both plasma and collisional frequencies, as well as the width of the plasma slab, on the EM wave propagation characteristics are discussed. The results can help the further understanding of propagation behaviours of EM waves in nonuniform plasma, and applications of the interactions between EM waves and plasmas.

In this paper, we show theoretically and experimentally that the reactive quasiparticle tunnel current of the superconductor tunnel junction could be directly measured at specific bias voltages for the higher harmonics of the quasiparticle tunnel current. We used the theory of quasiparticle tunneling to study the higher harmonics of the quasiparticle tunnel current in superconducting tunnel junction in the presence of rf irradiation. The impact of the reactive current on the harmonic behavior of the quasiparticle tunnel current was carefully studied by implementing a practical model with four parameters to model the dc I-V characteristics of the superconducting tunnel junction. The measured reactive current at the specific bias voltage is in good agreement with our theoretically calculated reactive current through the Kramers-Kronig transform. This study also shows that there is an excellent correspondence between the behavior of the predicted higher harmonics using the previously established theory of quasiparticle tunnel current in superconducting tunnel junctions by J.R. Tucker and M.J. Feldman and the measurements presented in this paper.

Polyurethane is a promising candidate for the potting of embedded electronics due to its shock absorbing properties. This paper discusses the less known strain hardening and shock mitigation properties of 4,4′-methylenediphenyl diisocyanate based polyurethane under dynamic loading. This study is reported in a strain rate range of 1600–2900 s−1 under compression using a split-Hopkinson pressure bar (SHPB). The experimental stress–strain behavior of polyurethane was modeled with Hollomon’s equation to analyze its hardening behavior in dynamic environments. Jointly, the incident, reflected, and transmitted strain signals of the SHPB are analyzed in time and frequency domains to understand the shock absorbing properties of polyurethane. Polyurethane was found to absorb more shock for more intense loading. It was observed to mitigate 81% of shock energy with frequencies up to 10 kHz.

The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of two fields can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory., Comment: 11 pages, minor changes

The basic particle electron obeys various theories like electrodynamics, quantum mechanics and special relativity. Particle under different experimental conditions behaves differently, allowing us to observe different characteristics which become basis for these theories. In this paper, we have made an attempt to suggest a classical picture by studying the requirements of these three modern theories. The basic presumption is: There must be certain structural characteristics in a particle like electron which make it obey postulates of modern theories. As it is ‘difficult’ to find structure of electron experimentally, we make a mathematical attempt. For a classical approach, we require well defined systems and we have studied a system with two charged particles, proton and electron in a hydrogen atom. An attempt has been made to give a model to describe electron as seen by the proton. We then discuss how the model can satisfy the requirements of the three modern theories in a classical manner. The paper discusses basic aspects of relativity and electrodynamics. However the focus of the paper is on quantum mechanics.

Laser shock peening (LSP) can induce the compressive residual stress (CRS) on the surface of the material, and surface nanocrystallization can be realized with a nanocrystal layer, thereby significantly improving the high-cycle fatigue performance. However, due to weak material constrain and the high working temperature of thin aero-engine compressor blades, CRS and refined grain structure are more likely to result in stress relaxation and microstructural recovery under thermal stress load, resulting in reducing the anti-fatigue effect of LSP. In this paper, on the basis of the surface nanocrystallization induced by LSP, residual stress and microstructure of TC11 titanium alloy thin components were measured and observed. The residual stress relaxation was characterized and the microstructure evolution was discussed. Also, the thermal stability mechanism of CRS and the nanostructure on the surface were analyzed. The experimental results show that after thermal loads, the CRS was decreased, and the stress relaxation amplitude was increased with an increase in temperature. After annealing at 400 °C, the dislocation density was significantly reduced, but the grain sizes of surface nanostructure did not greatly increase. After annealing at 400 °C for 2 h, the fatigue strength of the LSPed specimen was reduced compared with that before annealing, but it was still increased compared with the original state without LSP, especially under high-power density for multiple LSP treatment. It can be concluded that the surface nanostructure has good stability and effectively retards the initiation of fatigue cracks on the surface, which ensures the effectiveness of LSP under thermal loads.

This paper describes an improved modeling and simulation analysis of a variable-length reel take-up system for hose retrieval/deployment during aerial refueling. Based on a previously developed finite segment model, full reel acceleration is applied to the first rigid link connected to the towing point. The variation in the length of the hose and its rate of change are distributed evenly across all of the hose segments through a re-discretization technique, and the dynamics of the hose’s motion are regarded as a series of quasi-static processes. First, numerical simulations of the steady-state trailing hose are compared with previous results and flight data. The non-linear dynamics of a variable-length hose–drogue system during aerial refueling are then analyzed under various retrieval/deployment conditions. The results indicate that the finite segment model is prone to inducing chain-link oscillations in the hose dynamics, which are not appropriate for such a flexible body. In two application cases, the non-physical oscillations were well filtered using the proposed method, achieving a simultaneous combination of accuracy, stability, and robustness. Several advantages of the simulated hose dynamics provide a theoretical basis and platform for subsequent research into control strategies for suppressing the hose whipping phenomenon during hook-up.

A mechanically reconfigurable reflector (MRR) can adapt its geometry to facilitate a space antenna’s ability to scan along different angles. The reflector geometries corresponding to various scanning angles are calculated by coordinate change. The proper mechanical properties of the MRR are important for reconfiguration accuracy and actuation of the reflector system. The ratio of bending stiffness to Young’s modulus (D/E) is an essential parameter for the smooth reshaping of the MRR. In previous MMR research, materials with a small Young’s modulus were used, and the D/E ratio is increased by increasing shell thickness. In order to increase the D/E ratio while maintaining a thinner shell thickness, this paper proposes an auxetic lattice material for a reconfigurable reflector shell. The auxetic lattice material allows the raw material of the reflector shell to have a high Young’s modulus resulting in a smaller thickness. By optimizing the stacking sequence of carbon fiber composite, the bending stiffness of raw material is improved. Compounding the stacking sequence with elliptic voids array structure in reflector shell, the in-plane effective Young’s modulus is significantly decreased while maintaining a small decrease in bending stiffness. For a given target shape, the geometric parameters of the elliptic void are determined by the comparison of the reshaping accuracy calculated through simulation.

Mediating the divergent interest of vehicle stability and strengthened path tracking performance when aiming at the design of a path tracking controller for autonomous vehicles is a challenging issue. Accordingly, this paper proposes an improved-LQR (linear quadratic regulator) control applied using an improved path planning algorithm. A feedforward and feedback LQR control is constructed by applying the path optimization solution method, which is a different traditional polynomial trajectory fitting method, and then solving the path planning information and the control input parameter in real time to make the tracking error as convergent as possible. To verify the superiority of the improved-LQR, this study compares the proposed controller and model predictive control by the traditional path solving method on a closed-loop test road using Carsim/Simulink. The comparative results show the efficiency, accurate tracking, vehicle stability, and reliability of the proposed controller.

The NanChang Spherical Tokamak (NCST) is a new compact tokamak (with an aspect ratio of R/a = 1.67) for exploring the merging compression by which the plasma start-up is highly efficient. In this paper, a magnetic diagnostic system is designed, calibrated, and constructed on the NCST to meet the requirements of measurements. Based on detailed testing and analysis, the reliability of the sensors is guaranteed by optimizing the support structure and installation process. In addition, high-precision positioning equipment is utilized to ensure the installation accuracy of the sensors. During the start-up phase of the NCST, plasma currents on the order of a few kiloamperes were measured despite that the commensurate signal of eddy current is also found in the conducting structure. The magnetic diagnostic system is now completely operational and meets the requirements of the physical analysis on the NCST.

In this paper, the dielectric breakdown properties in SF6/CO2 mixed gas, the development of the streamer in SF6/CO2 mixed gas, and the distribution of each component with time were studied. First, the electron transport parameters (mean energy, longitudinal diffusion coefficients, Townsend coefficient, critical reduced electric field coefficients, and electron energy distribution function) in SF6/CO2 mixtures with different ratios in the E/N range of over 50–1000 Td were obtained by two-term Boltzmann equation analysis. Then, coupled with the Boltzmann drift–diffusion equation and Poisson equation, the hydrodynamic model of discharge of SF6/CO2 mixtures in a strongly non-uniform electric field was established. Many different influence factors are considered, such as the gas mixture ratio, applied voltage, space temperature, space pressure, and electrode structures. The results indicate that the increase in SF6 content in the mixed gas will reduce the ionization rate of the total mixed gas, and therefore, it takes a longer time for breakdown. The higher the pressure, the more concentrated the form of the streamer. As the temperature increases, the shape of the streamer head becomes more scattered, and it loses its contoured shape at about 3000 K; in addition, the existence of the maximum electron number density value appears at the tip of the rod electrode rather than at the streamer head. The simulation also revealed that the dielectric strength of SF6/CO2 mixtures is stronger than that of SF6/N2 mixtures and reached a turning point at an SF6 ratio of 60% under extremely non-uniform electric fields, which agreed well with experiments.

Owing to continual advances in computational fluid dynamics, simulations of fluids have emerged as an important means of analyzing the aerodynamic characteristics of flapping-wing flight. This study establishes an aerodynamic model of bionic flapping-wing flight and uses dynamic hybrid grid technology to divide its flow field and other parts. We formulate equations to control the discretized flow field and combine the Navier–Stokes equation (N–S equation) with the theory of dynamic vortices to solve the flow field of the motion of flapping wings. We analyzed the lift and drag generated by the flapping wing at different wind speeds, amplitudes, frequencies, and chordal torsion angles. The results show the following: (1) wind speed had a significant influence on the lift resistance of the flapping wing. When the wind speed was 1 m/s, the lift force was 1.544 N and increased 4.3 times to 6.636 N when the wind speed was 5 m/s. The resistance increased from 0.39 to 0.88 N. (2) Changes in the amplitude of flutter had little effect on the average lift resistance. When the amplitude was increased from 15° to 45°, the lift force increased to only 0.757 N and drag changed by little. (3) The increase in the flapping frequency improved flight lift. When the frequency was increased from 1 to 5 Hz, the lift increased by 2.9 N (1.78 times) and resistance increased by only 0.08 N. (4) Increasing the chord torsion angle increased flight lift. The lifts at β = 5° and 15° were 6.636 and 6.654 N, respectively, 0.85 and 0.87 N greater than those at β = 0°. As the torsion angle continued to increase, the lift decreased, while the resistance increased more quickly. When β = 15°, the resistance increased by 1.53 N, 9.6 times larger than that at 0°. Increasing the flight speed and flapping frequency can increase flight lift. A small increase in the chord torsion angle increased flight lift, but an excessively large angle led to a substantial increase in drag. Increasing the amplitude of flapping can increase the instantaneous lift generated but has a smaller effect on the average lift. By revealing the influence of different parameters on the lifting resistance of a flapping wing during flight, this paper provides a theoretical foundation for the design and control of bionic flapping-wing aircraft.